91 5.0 No Injector Pulse

hello. i've been using the checklist and some other threads and just wanted to get a second opinion before i go further. i'll briefly cover what i've done so far.
the car is a 91 lx with a 5 speed. ran like a champ last year, hasn't had any work or anything done to it in the interim.
the car sat outside all winter. i started it in february, and it ran like a champ. let it idle for a few minutes and shut it down.
a couple weeks ago i went out to drive it, and no start.
i sprayed some starting fluid in the vacuum line to the brake booster, and it fired right up.
checked injectors with a noid light, and got no pulse.
injectors have 12.3v (current battery voltage)
tps voltage is .99v.
fuel pump runs and primes, fuel pressure at rail. when i jumper at the self test connector, the pump runs continuously and sounds fine.
when i key on, the check engine light lights up very briefly, and then stays off. when jumpering the self test connector and keying on, there is no flash whatsoever.
also, if i leave the key on, every couple seconds, the fuel pump will clunk as if it's trying to prime again, but the MIL stays off. sometimes it will clunk twice or three times in rapid succession.
at first i thought that perhaps the eec relay was kicking on and off, but the power to the injectors and the tps are both constant, they do not kick on and off. and when i jumper the tester the pump runs constantly.
i'm thinking the eec might just be fried.
thoughts?

thanks in advance for any help. this site has been a great resource for various issues in the past, and is again for this one, but i thought my specific weirdness in this case warranted a question. lol
 
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Do the checklist below. No injector pulse is usually a PIP problem.

Fuel injectors inoperative, one or more injectors either on all the time or will not squirt.

Revised 27-Jan-2008 to include expanded testing for proper power to injector wiring


Tools needed: Noid light, Multimeter (volts & ohms), 10 MM socket &
extension, & ratchet.

Note: Do all of the steps and do them in order. The results of the subsequent tests are based on the prior tests being successfully passed.

1.) Each injector has a red power wire to provide power to the injector. Turn the ignition switch to Run and remove each injector electrical connector and use the Multimeter to check for 12 volts on the red wire. Each injector should have 12 volts +/- .5 volt. More voltage is always better than less voltage. No 12 volts on a singe injector and the wiring for that injector is broken inside the engine fuel injector harness.

No 12 volts on all injectors:
A.) Check for a bad connection at the 10 pin connector. Check for 12 volts at red wire on the MAF or TAD/TAB solenoids mounted on the aft side of the passenger strut tower. Good 12 volts there and you have a wiring problem with the 10 pin connectors or associated wiring.

See the graphic for the location of the 10 pin connectors:
TPS_IAB_Pic.jpg


See the graphic for the 10 pin connector circuit layout.
salt-pepper-10-pin-connectors-65-jpg.68512


The injector power pin is the VPWR pin in the black 10 pin connector.


B.) Bad ECC power relay. The relay is on top of the computer, it provides power to the fuel injector system.
It is somewhat difficult to get to, since it requires you to remove the computer from its 2 bolt mounting.. If the relay or socket is bad, you will not have 12 volts on any of the red wires in the engine compartment or to pins 37/57 on the computer. The pins 37/57 are the main power feed to the computer.
fuel-alt-links-ign-ac.gif


C.) Blown fuse link – The blue fuse link for the computer is up near the starter solenoid. Check for no 12 volts on the ECC relay socket or computer black/orange wires. No 12 volts and the fuse link is blown open. If the fuse link blows, there is no power for any of the computer functions.

D.) Bad wiring. Broken or damaged red wire to the chassis side of the 10 pin connectors.



Some basics about the computer:
Remember that the computer does not supply power for any actuator or relay. It provides the ground necessary to complete the circuit. That means one side of the circuit will always be hot, and the other side will go to ground or below 1 volt as the computer switches on that circuit.


2.) Get a noid light form AutoZone or other auto parts store, or even better
a set of them
24238.jpg

This set is from http://www.toolking.com/ProductInfo.aspx?productid=12492 and costs about $25.

3.) Use the noid light to determine that the injector pulses and isn’t stuck in the on position.
It you have a set of them install all of them and compare the pulse intensity. Install the noid lights, turn the ignition switch to Run and crank the engine. A light that doesn’t pulse and stays on has a short to ground in the computer side of the circuit. That can be either a wiring fault or a failed computer.
If this is the case, remove the passenger side lick panel and disconnect the computer connector.
There is one 10 MM bolt holding it in place. Pull the connector all the way out of the computer so that you can see the computer side pins.

eec04.gif


Use the list from the graphic below to find the fuel injector pins for the injectors that
didn’t turn the noid light off.

88-91_5.0_EEC_Wiring_Diagram.gif


4.) Set the Multimeter to low scale Ohms and measure between the computer ground located below the computer and the suspect fuel injector pins. You should see greater than 100 K Ohms resistance. If you see less than 100 Ohms, the wiring between the injector and the computer has a short to ground and needs service.
Check the harness and look for damage, kinks or frayed spots.

5.) A single noid light that never turns on is either a wiring fault, or a failed computer. Either the injector has no DC power or the computer has failed and cannot switch the injector circuit to ground. Determine if the injector has power by using the Multimeter to check for 12 volts on the red wire on the suspect injector connector. No 12 volts and you have a wiring fault.
Check the harness and look for damage, kinks or frayed spots. Check the 10 pin salt & pepper shaker connectors for bent pins, corrosion and damage.

See http://oldfuelinjection.com/?p=85 for some help on cleaning and tightening up the 10 pin connectors.

If none of the noid lights flash and you have 12 volts at each injector, check to see that you have good spark. Before you even think about replacing the computer, see step 6.

Next Check the fuel injector wiring end to end. Each fuel injector has a red wire (power) and an non-read wire (computer controlled ground). Set the Multimeter to low ohms and measure each non red fuel injector wire from the fuel injector connector to the matching pin on the computer connector. You should see less than 2 Ohms. More than that means a bad connection or bad wiring.


6.) Use an ohmmeter set on the low resistance scale and measure the resistance of each injector across the two contacts inside the electrical connector. You should see between 11-16 ohms. More or less than that is a bad injector. Next measure between either one of the contacts and the metal on the injector body. You should see greater than 100,000 ohms. Don’t hold the metal probe tips with your bare hands when you make this measurement. It will give incorrect results if you do.

Once you have determined that the suspect injectors have good power and good wiring, the computer is the likely suspect, since a ground is required to complete a circuit and make it function. The computer provides the ground: if doesn’t, then the noid light will not flash.

7) If you have gotten this far, then the problem is likely ignition related. Remember the noid test using all of the noid lights? All of them were supposed to be equally bright. Since you have already tested all the electrical side of the fuel injector circuit, the one remaining common item is the pip sensor inside the distributor. A failing pip sensor, damaged shutter wheel or bent distributor shaft could all cause the pulse delivered to the injectors to be faulty. A bad pip sensor will cause all the injectors not to fire and you will have no spark. Dumping the codes will usually show a code 14.


8) Spark plugs indicate one or more cylinders not firing: use the Multimeter to measure the resistance of the spark plug wires. The wires should measure 2000 ohms per foot of length. A 2 foot wire would be 4000 ohms and a 3 foot wire would be 6000 ohms. Some Taylor and Accel wires have metal cores and will measure much less: that’s OK.
Next examine the spark plug wires very carefully for burn spots, cracks and damaged insulation. One good thing to try is to start the engine while the car is a very dark area, open the hood and look for sparks or blue glow. They indicate the electricity is leaking out of the spark plug wires.

Thanks to Tmoss & Stang&2birds at www.veryuseful.com/mustang/tech/engine/ for some of the graphics
 
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ok, i finally got outside to work on the car a little more today.

i disconnected the eec connector and checked the grounds on the 3 injectors i could easily reach, and all was well, they have continuity and showed no resistance to speak of.
i verified the computer grounds.
after that i hooked the connector back up, and just to double check and because i now have a spark voltage tester, i hooked it up and had my wife crank the engine. imagine my surprise when after cranking a few seconds it tried to start!
i hooked the plug wire back up, and got in the car, and realized that the fuel pump is now running all the time with key on.
i did get the car to start, and it ran pretty poorly, rich, rough idle, wouldn't rev, started cutting and popping over about 1500 rpm.
after i ran it for a couple minutes and shut it down, i tried running codes, which still wouldn't work, and the check engine light would never turn off, even after sitting with KOEO for a few minutes. (i was so dumb-founded when it was running that i didn't think to check then)
after a few more key cycles, it went back to the condition from my first post, all the same symptoms. i unhooked the computer again, and hooked it back up, and it went back to running the pump constantly and would run poorly.

ok long story short, i removed the computer from the car, and heard something rattling around inside! I brought it in the house, and opened it up, and found this:
2014-08-10 17.29.47.jpg


now, obviously this computer is fried, and i need a new one. my concern is, do you have any idea what would've caused this? i don't want whatever it was to repeat.

here's a second view showing the whole board, and what looks like maybe light heat damage near the rear port. all the traces on the board look good, however, so i'm not sure if it's just discoloration from something else.
2014-08-10 17.36.42.jpg

you can just see the diode that burnt/broke off at the bottom of the photo.

thoughts?
thanks,
Eric
 
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Unless you are really good at electronics, I would suggest you either look for a source to get the current computer repaired or a replacement. Try eBay, I heard that there is a repair service that is reasonable. You send them your computer, they send it back repaired for a fixed price. Caps fail due to time and age, and if one goes, most of the rest are probably marginal as well.

If you are a skilled electronics technician, http://www.digikey.com/product-search/en/capacitors/aluminum-capacitors/131081?k=electrolytic cap is a good source for parts. Look for replacement caps with a 105 degree C temp rating and the longest lifetime at 105 C temp. You can use a higher voltage rating, but not a lower voltage rating.
 
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Thanks for the info. I don't think it's something I want to tackle myself, as I haven't really done much soldering. There's a couple electronics repair shops in the area i might have talk to. Otherwise I'll probably just go with a reman.
Thanks again
 
ok, this problem is still ongoing.
i bought a computer from a reputable user on another site, and installed it. got the same basic issues as the old computer. the current condition is as follows:
the car will start, but runs like complete crap. it's missing, and blowing some black smoke, and when attempting to rev it slightly, it shakes and misses badly.
the fuel pump still runs constantly in koeo. with the computer unhooked, it does not run. with the computer hooked up, and the icm unplugged, it still runs.
with koeo, the mil stays on constantly, and never shuts off. i can not get any flash when jumpering the self test connector.

after all my earlier testing, the only thing i had not really verified was the pip signal, because i assumed since it had spark, it had pip.
i checked the continuity of the pip from the icm plug to the 60 pin, and continuity was there, with no undue resistance.
however after some further research i've read about the necessity for 6.5v pip for proper injector pulse. i do not have a graphing dvom, but when connecting my meter and viewing the max voltage, the highest i've gotten is about 6.55, with several hitting in the low 6v range prior to reaching that point.

do you think it's possible that the pip is barely sufficient for pulse, and that i'm getting intermittent injector pulse or something because of it?
my training has always been that if you replace a part and get the same problem as before, that the part was not the problem. as such i'm reluctant to condemn this computer immediately, though i regret buying a used one instead of a reman, just because of the ease of swapping it for a different one.

i'm getting pretty frustrated with this issue. i have training in diagnostics and repair, and don't usually get stumped, but this thing is really killing me. some insight would really be appreciated.
thanks
Eric
 
You may have multiple problems. Let's start with the computer first.

No flash when dumping the codes.

Computer will not go into diagnostic mode on 91-95 model 5.0 Mustangs

Revised 7-June-2014 to change resistance figures to wiring checks

How it is supposed to work:
The grey/red wire (pin 46) is signal ground for the computer. It provides a dedicated ground for the EGR, Baro, ACT, ECT, & TPS sensors as well as the ground to put the computer into self-test mode. If this ground is bad, none of the sensors mentioned will work properly. That will severely affect the car's performance. You will have hard starting, low power and drivability problems. Since it is a dedicated ground, it passes through the computer on its way to the computer main power ground that terminates at the battery pigtail ground. It should read less than 1 ohm when measured from anyplace on the engine harness with the battery pigtail ground as the other reference point for the ohmmeter probe.

What sometimes happens is that the test connector grey/red wire gets jumpered to power which either burns up the wiring or burns the trace off the pc board inside the computer. That trace connects pins 46 to pins 40 & 60.

The STI (Self Test Input ) is jumpered to ground to put the computer into test mode. Jumpering it to power can produce unknown results, including damage to the computer. The ohm test simply verifies that there are no breaks in the wiring between the test connector and the computer input.

How to test the wiring :
With the power off, measure the resistance between the computer test ground (grey/red wire) on the self- test connector and battery ground. You should see less than 1 ohm.

attachment.php


If that check fails, remove the passenger side kick panel and disconnect the computer connector. There is a 10 MM bolt that holds it in place. Measure the resistance between the grey/red wire and pin 46 on the computer wiring connector: it should be less than 1 ohm. More than 1 ohm is a wiring problem. If it reads 1 ohm or less, then the computer is suspect. On the computer, measure the resistance between pin 46 and pins 40 & 60: it should be less than 1 ohm. More than that and the computer’s internal ground has failed, and the computer needs to be repaired or replaced.

See http://www.stangnet.com/mustang-forums/749974-computer-issue.html#post7490537 for Joel5.0’s fix for the computer internal signal ground.

If the first ground check was good, there are other wires to check. Measure the resistance between the STI computer self-test connector (red/white wire) and pin 48 on the computer main connector: it should be less than 1.5 ohms. More than 1 ohms is a wiring problem

The following is a view from the computer side of the computer wiring connector: it is for an A9L, A9P computer.
eec-iv-computer-connector-for-5-0-mustang-gif.88243


a9x-series-computer-connector-wire-side-view-gif.71316


Diagram courtesy of Tmoss & Stang&2birds

Check out the diagram and notice all the places the grey/red wire goes. Almost every sensor on the engine except the MAF is connected to it.
91-93 5.0 Mustangs
91-93_5.0_EEC_Wiring_Diagram.gif




Complete computer, actuator & sensor wiring diagram for 94-95 Mass Air Mustangs
94-95_5.0_EEC_Wiring_Diagram.gif



See the graphic for the 10 pin connector circuit layout.
salt-pepper-10-pin-connectors-65-jpg.68512



See the following website for some help from Tmoss (diagram designer) & Stang&2Birds
(website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine
 
Did you use a test light on pin 1 (PIP) Dark Blue wire on the tfi module while cranking it? The test light will flash. When it does, that that signal is sent to the PCM, which in turn pulses ground to the injectors to fire them. If no blinking light, no pulse to PCM.
 
You may have multiple problems. Let's start with the computer first.

How to test the wiring :
With the power off, measure the resistance between the computer test ground (grey/red wire) on the self- test connector and battery ground. You should see less than 1 ohm.

If the first ground check was good, there are other wires to check. Measure the resistance between the STI computer self-test connector (red/white wire) and pin 48 on the computer main connector: it should be less than 1.5 ohms. More than 1 ohms is a wiring problem
Computer test ground: .5 ohm to negative battery post
STI to pin 48: .2 ohm

the computer ground near the battery was in pretty nasty shape, which i'd seen a while ago, and planned on cleaning up, so today i pulled it, sanded off the paint and undercoating the previous owner sprayed all over it, and used a through bolt and nut to get a nice solid connection. i had checked the resistance from it to the battery previously though, and it was a couple tenths of an ohm prior to clean up.

triple checked after the pinouts, and still no self test, MIL still lights constantly in KOEO, never shuts off. this time i stared at it for 30 or 40 seconds, just to be triple canine certain.

i am eagerly awaiting the next step. not sure i can express how much i appreciate having someone with a deep understanding of this stuff to help me out.
 
Hello again. Due to life being life and me being lazy, it's been a year since i've worked on this car. I went out today and messed around with it. I installed the new distributor i had ordered from last year, figuring just in case the pip was bad, and while it seemed to run just a hair smoother, the check engine light was still on, and koeo the fuel pump still ran constantly.
i let the car run for a while to circulate the oil and get some warmth in the engine, and because i needed to move it, and it ended up idling for about ten minutes or so. At one point the check engine light suddenly turned off, and it started running right. Throttle response was crisp, it didn't stumble at all, revved smoothly, and returned to idle without stumbling or trying to die. It ran that way for another minute or two and i shut it down.
When i restarted it, it went back to solid CEL and running rich and rough. I let it run for a few minutes again, and after a while it again cleared up, and the light went out. And once again, shutting it down and restarting it returned it to running poorly.
After that, i left it koeo, and the light was on with the fuel pump running continuously as before. I wiggled the ten pin connectors, pulled them from the mounts and shook the wires and them, wiggled all the wiring to all the sensors, etc, and nothing changed.
Three times though, when i wasn't actually touching or wiggling anything, the fuel pump stopped, and the CEL went out. I didn't restart it at those times, but i cycled the key, and each time it continued running the pump and lighting the CEL, for a random amount of time, before finally stopping the pump and light.
I was and still am planning on cleaning and tightening the ten pin connectors, and until it started raining, i was going to try to get the light to go out/pump to stop, and then try to run the self test.
I guess this wasn't a very helpful update, but that's where i am today. Does this seem like the computer itself, maybe?
Thanks again
Eric
 
When the CEL come on, dump the codes...

Dump the codes: Codes may be present even if the Check Engine Light (CEL) isn't on.

Dumping the computer diagnostic codes on 86-95 Mustangs

Revised 26-July-2011. Added need to make sure the clutch is pressed when dumping codes.

Codes may be present even if the check engine light hasn’t come on, so be sure to check for them.

Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

Post the codes you get and I will post 86-93 model 5.0 Mustang specific code definitions and fixes. I do not have a complete listing for 94-95 model 5.0 Mustangs at this time.

Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. On a manual transmission car, be sure to press the clutch to the floor.
Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.

Underhoodpictures007-01.jpg


Underhoodpictures010.jpg


If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

attachment.php


The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.

attachment.php


The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.


WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems. This is crucial: the same wire that provides the ground to dump the codes provides signal ground for the TPS, EGR, ACT and Map/Baro sensors. If it fails, you will have poor performance, economy and driveablity problems

Some codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off, and clutch (if present) is pressed to the floor, and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

Your 86-88 5.0 won't have a working Check Engine Light, so you'll need a test light.
See AutoZone Part Number: 25886 , $10
4




Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see Equus Digital Ford Code Reader (3145) Equus - Digital Ford Code Reader 3145.
It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $22-$36.
41P3GQVDSHL._SS270_.jpg
 
When the CEL come on, dump the codes...

Dump the codes: Codes may be present even if the Check Engine Light (CEL) isn't on.

Dumping the computer diagnostic codes on 86-95 Mustangs

Revised 26-July-2011. Added need to make sure the clutch is pressed when dumping codes.

Codes may be present even if the check engine light hasn’t come on, so be sure to check for them.

Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

Post the codes you get and I will post 86-93 model 5.0 Mustang specific code definitions and fixes. I do not have a complete listing for 94-95 model 5.0 Mustangs at this time.

Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. On a manual transmission car, be sure to press the clutch to the floor.
Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.

Underhoodpictures007-01.jpg


Underhoodpictures010.jpg


If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

attachment.php


The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.

attachment.php


The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.


WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems. This is crucial: the same wire that provides the ground to dump the codes provides signal ground for the TPS, EGR, ACT and Map/Baro sensors. If it fails, you will have poor performance, economy and driveablity problems

Some codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off, and clutch (if present) is pressed to the floor, and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

Your 86-88 5.0 won't have a working Check Engine Light, so you'll need a test light.
See AutoZone Part Number: 25886 , $10
4




Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see Equus Digital Ford Code Reader (3145) Equus - Digital Ford Code Reader 3145.
It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $22-$36.
41P3GQVDSHL._SS270_.jpg
 
Thanks for your response.
This morning i was able to get it to dump KOEO codes, but i couldn't get it to start, and the battery is on the charger now. I'll see if i can get it started tomorrow morning.
KOEO codes are:
21
24
85
It's 35 degrees outside this morning, fyi.
When i would key on, it was still running the fuel pump continuously, and would stop it and begin the self test at completely random intervals. Once, it stopped the pump and started flashing the codes after 14 seconds, and several other times ranging from 40 seconds to over a minute. but, aside from one time when i cycled the key after about two minutes, it did eventually stop the pump and kick into self test mode every time i keyed on.
There were a couple of times where the pump would stop, then cycle on for a few more seconds, and then cycle on for a few seconds again after the codes had flashed through a couple times. It's like the computer was randomly restarting or something.
 
Two of the codes (21 & 24) are probably because of the cold weather outside, but here they are for reference sake.

The code 85 is missing gas vapor recycler.


Code 21 – ECT sensor out of range. Broken or damaged wiring, bad ECT sensor.
Note that that if the outside air temp is below 50 degrees F that the test for the ECT can be in error. Warm the engine up until you get good hot air from the heater and then dump the codes again.

The ECT sensor has absolutely nothing to do with the temperature gauge. They are different animals. The ECT sensor is normally located it the passenger side front of the engine in the water feed tubes for the heater.

The ACT & ECT have the same thermistor, so the table values are the same

ACT & ECT test data:

Use Pin 46 on the computer for ground for both ECT & ACT to get most accurate readings.

Pin 7 on the computer - ECT signal in. At 176 degrees F it should be .80 volts

Pin 25 on the computer - ACT signal in. At 50 degrees F it should be 3.5 volts. It is a good number if the ACT is mounted in the inlet airbox. If it is mounted in the lower intake manifold, the voltage readings will be lower because of the heat transfer.

a9x-series-computer-connector-wire-side-view-gif.71316


Voltages may be measured across the ECT/ACT by probing the connector from the rear. A pair of safety pins may be helpful in doing this. Use care in doing it so that you don't damage the wiring or connector.

Here's the table :

50 degrees F = 3.52 v
68 degrees F = 3.02 v
86 degrees F = 2.62 v
104 degrees F = 2.16 v
122 degrees F = 1.72 v
140 degrees F = 1.35 v
158 degrees F = 1.04 v
176 degrees F = .80 v
194 degrees F = .61
212 degrees F = .47 v
230 degrees F = .36 v
248 degrees F = .28 v

Ohms measures at the computer with the computer disconnected, or at the sensor with the sensor disconnected.

50 degrees F = 58.75 K ohms
68 degrees F = 37.30 K ohms
86 degrees F = 27.27 K ohms
104 degrees F = 16.15 K ohms
122 degrees F = 10.97 K ohms
140 degrees F = 7.60 K ohms
158 degrees F = 5.37 K ohms
176 degrees F = 3.84 K ohms
194 degrees F = 2.80 K ohms
212 degrees F = 2.07 K ohms
230 degrees F = 1.55 K ohms
248 degrees F = 1.18 k ohms

Diagram courtesy of Tmoss & Stang&2birds

88-91_5.0_EEC_Wiring_Diagram.gif


See the following website for some help from Tmoss (diagram designer) & Stang&2Birds
(website host) for help on 88-95 wiring Mustang FAQ - Wiring & Engine Info

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
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Code 24 - Intake Air Temperature (ACT) sensor out of range.
Bad sensor, bad wiring. The ACT for Mustangs built before 95 is in the
#5 intake runner. It measures the air temperature in the intake to help
computer the proper air/fuel ratio.

Note that that if the outside air temp is below 50 degrees F that the test for the ACT can be in error. Warm the engine up to operating temperature and retest.

ACT & ECT test data:

The ACT & ECT have the same thermistor, so the table values are the same

Pin 7 on the computer - ECT signal in. at 176 degrees F it should be .80 volts

Pin 25 on the computer - ACT signal in. at 50 degrees F it should be 3.5 volts.
It is a good number if the ACT is mounted in the inlet airbox. If it is mounted in
the lower intake manifold, the voltage readings will be lower because of the heat transfer.
Here's the table :

50 degrees F = 3.52 v
68 degrees F = 3.02 v
86 degrees F = 2.62 v
104 degrees F = 2.16 v
122 degrees F = 1.72 v
140 degrees F = 1.35 v
158 degrees F = 1.04 v
176 degrees F = .80 v
194 degrees F = .61
212 degrees F = .47 v
230 degrees F = .36 v
248 degrees F = .28 v

Ohms measures at the computer with the computer disconnected,
or at the sensor with the sensor disconnected.

50 degrees F = 58.75 K ohms
68 degrees F = 37.30 K ohms
86 degrees F = 27.27 K ohms
104 degrees F = 16.15 K ohms
122 degrees F = 10.97 K ohms
140 degrees F = 7.60 K ohms
158 degrees F = 5.37 K ohms
176 degrees F = 3.84 K ohms
194 degrees F = 2.80 K ohms
212 degrees F = 2.07 K ohms
230 degrees F = 1.55 K ohms
248 degrees F = 1.18 k ohms


Code 85 CANP solenoid - The Carbon Canister solenoid is inoperative or missing.

Revised 11 –Jan_2015 to add warning about vacuum leaks due to deteriorated hose or missing caps on vacuum lines when the solenoid is removed.

Check vacuum lines for leaks and cracks. Check electrical wiring for loose connections, damaged wiring and insulation. Check solenoid valve operation by grounding the gray/yellow wire to the solenoid and blowing through it.
The computer provides the ground for the solenoid. The red wire to the solenoid is always energized any time the ignition switch is in the run position.

If you disconnected the carbon canister and failed to properly cap the vacuum line coming from under the upper intake manifold, you will have problems. You will also have problems if the remaining hose coming from under the upper intake manifold or caps for the vacuum line are sucking air.

Charcoal canister plumbing - one 3/8" tube from the bottom of the upper manifold to the rubber hose. Rubber hose connects to one side of the canister solenoid valve. Other side of the solenoid valve connects to one side of the canister. The other side of the canister connects to a rubber hose that connects to a line that goes all the way back to the gas tank. There is an electrical connector coming from the passenger side injector harness near #1 injector that plugs into the canister solenoid valve. It's purpose is to vent the gas tank. The solenoid valve opens at cruse to provide some extra fuel. The canister is normally mounted on the passenger side frame rail near the smog pump pulley.

attachment.php


It does not weigh but a pound or so and helps richen up the cruse mixture. It draws no HP & keeps the car from smelling like gasoline in a closed garage. So with all these good things and no bad ones, why not hook it up & use it?


The purge valve solenoid connector is a dangling wire that is near the ECT sensor and oil filler on the passenger side rocker cover. The actual solenoid valve is down next to the carbon canister. There is about 12"-16" of wire that runs parallel to the canister vent hose that comes off the bottom side of the upper intake manifold. That hose connects one port of the solenoid valve; the other port connects to the carbon canister.

The purge valve solenoid should be available at your local auto parts store.

Purge valve solenoid:
6



The carbon canister is normally mounted on the passenger side frame rail near the smog pump pulley.
Carbon Canister:
CP2000photo%20primary__ra_p.jpg
 
I was able to get the car started this morning. However it would never return to normal and give codes.

The ECT voltage prior to starting was 3.65, and the ACT was 3.57. Neither seem out of line if 3.50 is 50 degrees.

The carbon canister is gone, which i suspected. Sometime earlier in the car's life someone removed it, and i don't have one to reinstall. i haven't traced the wiring yet to see how much is left.

I also double checked the MAF voltage at idle, around 1.08, and the TPS is at 1.0. I checked the BAP voltage, however when i looked for a voltage chart, i see that it should be checked for frequency. my dvom has a frequency function, so i'll check that out tomorrow. Although i did disconnect it, and then restart the car, to see if it would act any different, and it ran exactly the same.
 
Sorry to thread jack..i ran a noid test on the driver side injector harness. Number 8 stays on and is brighter than the 5 6 or 7. This is after i swapped to a known working injector harness. Im guessing another computer that works should solve that issue? I did run codes and i recieved a code 11. What else could cause the brighter noid light issue on number 8?
 
@fredfifty

If the noid light is always on, that means the injector stays turned on; it never turns off.
If it isn't clogged, it is constantly squirting fuel.
There probably is a short to ground in that injector harness.



I'm fixing to dump a lot of very technical stuff on your plate, so you may want to print it out and highlight the sections that relate to your current problem.


For your particular problem start at Step 3 below...

Fuel injectors inoperative, one or more injectors either on all the time or will not squirt.

Revised 11 Aug 2018 to clarify injector wiring continuity testing


Tools needed: Noid light, Multimeter (volts & ohms), 10 MM socket &
extension, & ratchet.

Note: Do all of the steps and do them in order. The results of the subsequent tests are based on the prior tests being successfully passed.

1.) Each injector has a red power wire to provide power to the injector. Turn the ignition switch to Run and remove each injector electrical connector and use the multimeter to check for 12 volts on the red wire. Each injector should have 12 volts +/- .5 volt. More voltage is always better than less voltage. No 12 volts on a singe injector and the wiring for that injector is broken inside the engine fuel injector harness.

No 12 volts on all injectors:
A.) Check for a bad connection at the 10 pin connector. Check for 12 volts at red wire on the MAF or TAD/TAB solenoids mounted on the aft side of the passenger strut tower. Good 12 volts there and you have a wiring problem with the 10 pin connectors or associated wiring.

See the graphic for the location of the 10 pin connectors:
TPS_IAB_Pic.jpg


See the graphic for the 10 pin connector circuit layout.
68512.jpg


The injector power pin is the VPWR pin in the black 10 pin connector. [/b]

B.) Bad ECC power relay. The relay is on top of the computer, it provides power to the fuel injector system. This is relevant ONLY if you do not have power to all injectors.
It is somewhat difficult to get to, since it requires you to remove the computer from its 2 bolt mounting.. If the relay or socket is bad, you will not have 12 volts on any of the red wires in the engine compartment or to pins 37/57 on the computer. The pins 37/57 are the main power feed to the computer.

fuel-alt-links-ign-ac.gif


C.) Blown fuse link – The blue fuse link for the computer is up near the starter solenoid. Check for no 12 volts on the ECC relay socket or computer black/orange wires. No 12 volts and the fuse link is blown open. If the fuse link blows, there is no power for any of the computer functions.

D.) Bad wiring. Broken or damaged red wire to the chassis side of the 10 pin connectors.



Some basics about the computer:
Remember that the computer does not supply power for any actuator or relay. It provides the ground necessary to complete the circuit. That means one side of the circuit will always be hot, and the other side will go to ground or below 1 volt as the computer switches on that circuit.


2.) Get a noid light from AutoZone or other auto parts store, or even better a set of them.
oes-25142_xl.jpg

This one is from http://www.summitracing.com/parts/oes-25142?seid=srese1&gclid=CMXk7M6dmM0CFdgOgQodGUMHWQ and costs about $6.

3.) Use the noid light to determine that the injector pulses and isn’t stuck in the on position.
It you have a set of them install all of them and compare the pulse intensity. Install the noid lights, turn the ignition switch to Run and crank the engine. A light that doesn’t pulse and stays on has a short to ground in the computer side of the circuit. That can be either a wiring fault or a failed computer. \

Disconnect all 8 fuel injector connectors from the injectors and leave them disconnected for steps 4-6.

If this is the case, remove the passenger side lick panel and disconnect the computer connector.
There is one 10 MM bolt holding it in place. Pull the connector all the way out of the computer so that you can see the computer side pins.

Use the list from the graphic below to find the fuel injector pins for the injectors that didn’t turn the noid light off.

71316.gif


88243


88-91_5.0_EEC_Wiring_Diagram.gif


4.) Set the multimeter to low scale Ohms and measure between the computer ground located below the computer and the suspect fuel injector pins. You should see greater than 100 K Ohms resistance. If you see less than 100K Ohms, the wiring between the injector and the computer has an internal short to ground and needs service.
Check the harness and look for damage, kinks or frayed spots. A Short to ground would result in an injector that never turned off.

5.) A single noid light that never turns on is either a wiring fault, or a failed computer. Either the injector has no DC power or the computer or wiring has failed and cannot switch the injector circuit to ground. Determine if the injector has power by using the multimeter to check for 12 volts on the red wire on the suspect injector connector. No 12 volts and you have a wiring fault.


If none of the noid lights flash and you have 12 volts at each injector, check to see that you have good spark. Before you even think about replacing the computer, see step 6.

Check the injector wiring for open circuit or broken wiring or bad connections.
Check the harness and look for damage, kinks or frayed spots. Check the 10 pin salt & pepper shaker connectors for bent pins, corrosion and damage.

Next check the fuel injector wiring for open circuits. Set the multimeter to low scale Ohms. Each fuel injector has a red wire (power) and a non-red wire (computer controlled ground).

Inside the car, take a short piece of 14 gauge bare wire and jumper it to the ground below the computer. Use the computer wiring diagram and select one of the injectors. The recommended procedure is to start with cylinder #1 and test each injector in numerical sequence 1,2,3, etc. Then stick the ground wire into the computer wiring harness socket for the injector you want to test. Don’t forget to move the ground inside the car each time you test a different injector.

Under the hood, set the multimeter to low ohms and ground one of the test leads to the engine block. Then measure the resistance between the non-red fuel injector wire in the fuel injector connector and the meter ground on the engine block. You should see less than 1 Ohm. More than that means a bad connection or bad wiring.

The 10 pin connectors are the first place to look for problems when it fails the above test.

Engine side testing Unplug the black 10 pin connector from its’ mating half. Use the 10 pin connector diagram in this tech note to locate the injector you are currently testing. Measure the resistance between the non-red injector wire and the injector pin on the engine mounted side of the fuel injector harness; you should see 1 Ohm or less. More than that indicates a broken wire or bad connection.

Body side testing Use the 10 pin connector diagram in this tech note to locate the injector you are currently testing. Again, the black connector that is connected to the car body side of the wiring harness is the one to use for this test. Make sure that you test the injector pin for the wire side of the computer wiring harness pin that you grounded. Ground one lead of the multimeter on the engine block and check the resistance; you should see 1 Ohm or less. Test all 8 injectors in numerical sequence, and move the grounding wire at the computer wiring harness each time you test a different injector.

6.) Use an ohmmeter set on the low resistance scale and measure the resistance of each injector across the two contacts inside the injector electrical connector. You should see between 11-16 ohms. More or less than that is a bad injector. Next, measure between either one of the contacts and the metal on the injector body. You should see greater than 100,000 ohms. Don’t hold the metal probe tips with your bare hands when you make this measurement; It will give incorrect results if you do.

Once you have determined that the suspect injectors have good power and good wiring, the computer is the likely suspect, since a ground is required to complete a circuit and make it function. The computer provides the ground: if doesn’t, then the noid light will not flash. If the noid light stays on, the computer has an internal failure.

7) If you have gotten this far, then the problem is likely ignition related. Remember the noid test using all of the noid lights? All of them were supposed to be equally bright. Since you have already tested all the electrical side of the fuel injector circuit, the one remaining common item is the pip sensor inside the distributor. A failing pip sensor, damaged shutter wheel or bent distributor shaft could all cause the pulse delivered to the injectors to be faulty. A bad pip sensor will cause all the injectors not to fire and you will have no spark. Dumping the codes will usually show a code 14.


8) Spark plugs indicate one or more cylinders not firing: use the multimeter to measure the resistance of the spark plug wires. The wires should measure 2000 ohms per foot of length. A 2 foot wire would be 4000 ohms and a 3 foot wire would be 6000 ohms. Some Taylor and Accel wires have metal cores and will measure much less: that’s OK.
Next examine the spark plug wires very carefully for burn spots, cracks and damaged insulation. One good thing to try is to start the engine while the car is a very dark area, open the hood and look for sparks or blue glow. They indicate the electricity is leaking out of the spark plug wires.

Thanks to Tmoss & Stang&2birds at www.veryuseful.com/mustang/tech/engine/ for some of the graphics

Thanks also to www.oldfuelinjection.com for some of the graphics.
 
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