Electrical Starting Issue... Confused 91 GT

[Shooter50]

91 GT convertible.. Been sitting for a while. But have never had this issue with other (fox) projects being dormant.. First problem, everything looks great at the starting relay.. but Im not getting the ground from the computer and the (inertia bypassed) pump does not run. (problem 1). HAVE a new pump, fuel filter and I get 40-42 lbs of pressure at the test valve, with the jumper wire to the diagnostic port.. I also have spark at the coil and plugs..
Fuel pressure and spark should give me enough to at least move the car. with the jumper, so I can dig in.. Turns over but wont start. Ideas?

 

[Steel1]

Have you had the distributor out lately, if so was it reinstalled at TDC ?

 

[General karthief]

Read and follow step by step.

Cranks OK, but No Start Checklist for Fuel Injected Mustangs

Cranks OK, but No Start Checklist for Fuel Injected 5.0 Mustangs model years 1986-1995 A word about this checklist before you start: it is arranged in a specific order to put the most likely failure items first. That will save you time, energy and money. Start at the top of the list and work...

www.stangnet.com

 

[Shooter50]

Have you had the distributor out lately, if so was it reinstalled at TDC ?

No, Ive never even messed with the timing on this car, motor/fuel system is all stock.

 

[Steel1]

karthief gave you a great checklist, I would start going through it and post results/questions.

 

[Shooter50]

Read and follow step by step.

Cranks OK, but No Start Checklist for Fuel Injected Mustangs

Cranks OK, but No Start Checklist for Fuel Injected 5.0 Mustangs model years 1986-1995 A word about this checklist before you start: it is arranged in a specific order to put the most likely failure items first. That will save you time, energy and money. Start at the top of the list and work...

www.stangnet.com

Well Ive done everything on that list and Im leaning towards "failed computer".

I'm getting power to everything that's supposed to have power. Have spark, Pump relay, injectors.

Not getting the ground from the computer to the (fuel pump) relay or ground at injector.

Off to pull the computer, probably check the ecc relay.. If there's a sticky for this stage id appreciate.

My problem is the car is backed into a corner (fence) and cant move it right now to get to the passenger side, gonna have to twist my back to get in there.. Good times..

 

[General karthief]

You pretty much have to get the right door open to get the kick panel off and get to the computer, if not you can break the plastic trim

 

[Shooter50]

You pretty much have to get the right door open to get the kick panel off and get to the computer, if not you can break the plastic trim

Yeah, I know where it is, Im at it from the inside of the car, looking for its relay first, dont see it yet. woof.. Also kind of surprised its a A9M.. Heard of them, but first one Ive come across and Ive seen a lot of these.. Figuerd it would be a A9L (its a stock manual), Might be some California Bull.. lol

 

[Shooter50]

Soo, I should have known. The usual suspects these days.. I’m gonna order some caps and hope it saves this computer... Also would be nice if anyone has any intel on computer models.. The forums are useless on this.. Either people get the most common backwards or guess about others.. my understanding was A9L were manual, A9P auto.. People still get that twisted so I don’t know jack about this A9M.. again a stock GT with manual.. Yet people suggest it’s an auto comp.

 

[Shooter50]

Bump..

So I have replaced capacitors on the Computer, they were toast, but still no luck..
Have crank and spark, computer relay works properly, power is correct at pump relay and injectors.
Still not getting (computer) ground at injectors or pump relay.. (fuel pump will run if I jump test ground)

Any test procedures for computer/harness connector? Other Ideas appreciated..

 

[Shooter50]

Bump..

So I have replaced capacitors on the Computer, they were toast, but still no luck..
Have crank and spark, computer relay works properly, power is correct at pump relay and injectors.
Still not getting (computer) ground at injectors or pump relay.. (fuel pump will run if I jump test ground)

Any test procedures for computer/harness connector? Other Ideas appreciated..

 

[Shooter50]

bump
@General karthief
anything?

 

[jrichker]

What I am hearing is that you read the Cranks OK but no Start checklist but didn't necessarily do all of the tests.
For the engine to not run, at least one of the tests has to fail. How do I know that? I am the guy who wrote the checklist...

The computer provides ground for all actuators, injectors and solenoids, it does not provide power to any of these items.

Are you getting a pulse at the injectors when using a noid light?

Is the computer main power ground connected?

Have you dumped the computer codes?





Computer & interchange information for 5.0 Mustang

Revised 16-Oct-2011 to add O2 sensor harness warnings

The Mass Air computers from 89-93 are interchangeable with a few exceptions. Just be sure you use the MAF & MAF sensor from the same series computer. The auto transmission computers use a different start circuit than the manual computers. You can use an auto trans computer in a 5 speed car with no problems or changes. I have done it in my original 89 Mustang GT, and I know it works OK. I would recommend avoiding using a 5 speed computer in an auto trans car due to the possibility of damaging the computer’ internal signal ground circuitry.

The odd duck is the 93 Cobra computer, labeled X3Z which is internally calibrated for 24 lb injectors. Use the MAF & MAF sensor from the X3Z computer to avoid problems with the computer's internal calibration. Try and avoid the 93 Cobra computer if you can.

Some cautions about O2 Sensor harnesses need to be observed to avoid damage to the computer.
Only run a 5 speed trans O2 harness with an A9L. Do not run an Auto O2 sensor harness with an A9L. Doing so will damage the computer’s internal signal ground.
Only run an Auto trans O2 sensor harness with an A9P in a car that has an Auto trans. Using a 5 speed trans O2 sensor harness with an Auto trans will cause no crank problems.
See http://forums.corral.net/forums/general-mustang-tech/1094179-oxygen-sensor- harnesses-manual-auto-differences-year-differences.html for more O2 sensor wiring harness info
If you have a damaged computer with signal ground problems, See http://www.stangnet.com/mustang-forums/749974-computer-issue.html#post7490537 for Joel5.0’s fix to the computer internal signal ground.

All the following are mass air unless they say Speed Density
8LD - MANUAL 88 5.0L Mustang Mass Air - California
8LF - Auto 88 5.0L Mustang Mass Air- California
8LG - Auto 88 5.0L Mustang Mass Air- California
A9L - 89-93 5.0L Mustang 5-spd Mass Air
A3M - 93 5.0L Mustang 5-spd Mass Air
A3M1 - 93 5.0L Mustang 5-spd Mass Air
X3Z - 93 5.0L Cobra 5-spd Mass Air internally calibrated for 24 lb injector
A9P - 89-93 5.0L Mustang Auto Mass Air
A9S - 88 5.0L Mustang California Mass Air
C3W - 89-93 5.0L Mustang Auto
DA1 - 87 5.0L Mustang 5-spd Speed Density
J4J1 - 94-95 5.0L SVT Cobra 5-spd
T4M0 - 94-95 5.0L GT Vert 5-spd
U4P0 - 94-95 5.0L GT Auto
W4H0 - 94-95 5.0L GT
ZA0 - 95 Cobra R
D9S - 88 Lincoln LSC Speed Density

 

[Olivethefet]

I had the same thing happen to my computer. I bought new capacitors and still had the same issue. I ended up sending my to Cardone. Actually I went to NAPA and then they sent it there. Maybe you have another issue, but if it comes down to it you can send it off.

 

[General karthief]

I'm with Alabama Nick on this one, if you went through the checklist (thanks again to jrichker) and did the steps, I should note: I had to do the checklist twice then again redo certain steps and it also was my computer, send it off or get another.
I got another (lucky) and down the road I go.

 

[Shooter50]

What I am hearing is that you read the Cranks OK but no Start checklist but didn't necessarily do all of the tests.
For the engine to not run, at least one of the tests has to fail. How do I know that? I am the guy who wrote the checklist...

The computer provides ground for all actuators, injectors and solenoids, it does not provide power to any of these items.

Are you getting a pulse at the injectors when using a noid light?

Is the computer main power ground connected?

Have you dumped the computer codes?





Computer & interchange information for 5.0 Mustang

Revised 16-Oct-2011 to add O2 sensor harness warnings

The Mass Air computers from 89-93 are interchangeable with a few exceptions. Just be sure you use the MAF & MAF sensor from the same series computer. The auto transmission computers use a different start circuit than the manual computers. You can use an auto trans computer in a 5 speed car with no problems or changes. I have done it in my original 89 Mustang GT, and I know it works OK. I would recommend avoiding using a 5 speed computer in an auto trans car due to the possibility of damaging the computer’ internal signal ground circuitry.

The odd duck is the 93 Cobra computer, labeled X3Z which is internally calibrated for 24 lb injectors. Use the MAF & MAF sensor from the X3Z computer to avoid problems with the computer's internal calibration. Try and avoid the 93 Cobra computer if you can.

Some cautions about O2 Sensor harnesses need to be observed to avoid damage to the computer.
Only run a 5 speed trans O2 harness with an A9L. Do not run an Auto O2 sensor harness with an A9L. Doing so will damage the computer’s internal signal ground.
Only run an Auto trans O2 sensor harness with an A9P in a car that has an Auto trans. Using a 5 speed trans O2 sensor harness with an Auto trans will cause no crank problems.
See http://forums.corral.net/forums/general-mustang-tech/1094179-oxygen-sensor- harnesses-manual-auto-differences-year-differences.html for more O2 sensor wiring harness info
If you have a damaged computer with signal ground problems, See http://www.stangnet.com/mustang-forums/749974-computer-issue.html#post7490537 for Joel5.0’s fix to the computer internal signal ground.

All the following are mass air unless they say Speed Density
8LD - MANUAL 88 5.0L Mustang Mass Air - California
8LF - Auto 88 5.0L Mustang Mass Air- California
8LG - Auto 88 5.0L Mustang Mass Air- California
A9L - 89-93 5.0L Mustang 5-spd Mass Air
A3M - 93 5.0L Mustang 5-spd Mass Air
A3M1 - 93 5.0L Mustang 5-spd Mass Air
X3Z - 93 5.0L Cobra 5-spd Mass Air internally calibrated for 24 lb injector
A9P - 89-93 5.0L Mustang Auto Mass Air
A9S - 88 5.0L Mustang California Mass Air
C3W - 89-93 5.0L Mustang Auto
DA1 - 87 5.0L Mustang 5-spd Speed Density
J4J1 - 94-95 5.0L SVT Cobra 5-spd
T4M0 - 94-95 5.0L GT Vert 5-spd
U4P0 - 94-95 5.0L GT Auto
W4H0 - 94-95 5.0L GT
ZA0 - 95 Cobra R
D9S - 88 Lincoln LSC Speed Density

Hey thanks, the checklist is great. The only thing i didn't do was the ether beause I'd moved on to the Injectors already.

I did use noid light, no pulse. Also used probe and meter to double check. Get 12v on constant to Injectors like they should but not getting ground on the other wire when cranking.

All the grounds are good, checked the one by the batt, the strap behind engine is good and the one right by the ECM harness.
From what i can tell using the wiring diagram I have, also checked and have gound at pins 20, 40, 60 and 49 right at the ECM connector.

Ive been disconnecting the battery when Im done each day, so I didn't think there would be any codes.

So yeah, not getting grounds at the injectors and have to jump the ground at the test port, to get ground at pump relay.

Thats what led me to the ECM, one capacitor leg was just cooked and the others looked bad. So I replaced them and still nothing. I dont see anything obvious on the board, and dont know how to test it. Was thinking about testing the caps with the ECM in the car, but I dont know what the values should be.

Thanks again.

PS, The link for the "ground signal" fix in that write up is dead

 

[jrichker]

Hey thanks, the checklist is great. The only thing i didn't do was the ether beause I'd moved on to the Injectors already.

I did use noid light, no pulse. Also used probe and meter to double check. Get 12v on constant to Injectors like they should but not getting ground on the other wire when cranking.

All the grounds are good, checked the one by the batt, the strap behind engine is good and the one right by the ECM harness.
From what i can tell using the wiring diagram I have, also checked and have gound at pins 20, 40, 60 and 49 right at the ECM connector.

Ive been disconnecting the battery when Im done each day, so I didn't think there would be any codes.

So yeah, not getting grounds at the injectors and have to jump the ground at the test port, to get ground at pump relay.

Thats what led me to the ECM, one capacitor leg was just cooked and the others looked bad. So I replaced them and still nothing. I dont see anything obvious on the board, and dont know how to test it. Was thinking about testing the caps with the ECM in the car, but I dont know what the values should be.

Thanks again.

PS, The link for the "ground signal" fix in that write up is dead

Dump codes sticky

Look at the top of the 5.0 Tech forum where the sticky threads are posted. One of them is how to dump the computer codes. Codes may be present even if the CEL (Check Engine Light) isn’t on. You don’t need a code reader or scanner – all you need is a paper clip, or if your lady friend has a hair pin, that will do the job.
I highly suggest that you read it and follow the instructions to dump the codes. http://www.stangnet.com/mustang-forums/threads/how-to-pull-codes-from-eec4.889006/

No pulse from the injectors is probably a PIP problem, may show a code 14 dumping the codes. Code 14 - Ignition pickup (PIP) was erratic – the Hall Effect sensor in the distributor is failing. Bad sensor, bad wiring, dirty contacts. Factory tach will sometimes read erratically.

Revised 8-Apr-2017 to correct SPOUT problem symptoms wording

The PIP is a Hall Effect magnetic sensor that triggers the TFI and injectors. There is a shutter wheel alternately covers and uncovers a fixed magnet as it rotates. The change in the magnetic field triggers the sensor. They are often heat sensitive, increasing the failure rate as the temperature increases.

PIP Sensor functionality, testing and replacement:
The PIP is a Hall Effect magnetic sensor that triggers the TFI and injectors. There is a shutter wheel alternately covers and uncovers a fixed magnet as it rotates. The change in the magnetic field triggers the sensor. A failing PIP sensor will often set code 14 in the computer. They are often heat sensitive, increasing the failure rate as the temperature increases.

Some simple checks to do before replacing the PIP sensor or distributor:
You will need a Multimeter or DVM with good batteries: test or replace them before you get started.. You may also need some extra 16-18 gauge wire to extend the length of the meter’s test leads.
Visual check first: look for chaffed or damaged wiring and loose connector pins in the TFI harness connector.
Check the IDM wiring – dark green/yellow wire from the TFI module to pin 4 on the computer. There is a 22K Ohm resistor in the wiring between the TFI and the computer. Use an ohmmeter to measure the wire resistance from the TFI to the computer. You should see 22,000 ohms +/- 10%.
Check the PIP wiring - dark blue from the TFI module to pin 56 on the computer. Use an ohmmeter to measure the wire resistance from the TFI to the computer. You should see 0.2-1.5 ohms.
Check the SPOUT wiring – yellow/lt green from the TFI module to pin 36 on the computer. Use an ohmmeter to measure the wire resistance from the TFI to the computer. You should see 0.2-1.5 ohms.
Check the black/orange wire from the TFI module to pin 16 on the computer. Use an ohmmeter to measure the wire resistance from the TFI to the computer. You should see 0.2-1.5 ohms.
Check the red/green wire; it should have a steady 12-13 volts with the ignition switch on and the engine not running.
Check the red/blue wire; it should have a steady 12-13 volts with the ignition switch in Start and the engine not running. Watch out for the fan blades when you do this test, since the engine will be cranking.
If you do not find any chaffed or broken wires, high resistance connections or loose pins in the wiring harness, replace the PIP sensor or the distributor.

The PIP sensor is mounted in the bottom of the distributor under the shutter wheel. In stock Ford distributors, you have to press the gear off the distributor shaft to get access to it to replace it. Most guys just end up replacing the distributor with a reman unit for about $75 exchange

PIP problems & diagnostic info
Spark with the SPOUT out, but not with the SPOUT in suggests a PIP problem. The PIP signal level needs to be above 6.5 volts to trigger the computer to pulse the fuel injectors, but only needs to be 5.75 volts to trigger the TFI module. Hence with a weak PIP signal, and the SPOUT in, you could get spark but no injector pulse. You will need an oscilloscope or graphing DVM to measure the output voltage since it is not a straight DC voltage.

See http://www.wellsmfgcorp.com/pdf/counterp_v8_i2_2004.pdf and http://www.wellsmfgcorp.com/pdf/counterp_v8_i3_2004.pdf for verification of this little detail from Wells, a manufacturer of TFI modules and ignition system products.

 

[Shooter50]

Dump codes sticky

Look at the top of the 5.0 Tech forum where the sticky threads are posted. One of them is how to dump the computer codes. Codes may be present even if the CEL (Check Engine Light) isn’t on. You don’t need a code reader or scanner – all you need is a paper clip, or if your lady friend has a hair pin, that will do the job.
I highly suggest that you read it and follow the instructions to dump the codes. http://www.stangnet.com/mustang-forums/threads/how-to-pull-codes-from-eec4.889006/

No pulse from the injectors is probably a PIP problem, may show a code 14 dumping the codes. Code 14 - Ignition pickup (PIP) was erratic – the Hall Effect sensor in the distributor is failing. Bad sensor, bad wiring, dirty contacts. Factory tach will sometimes read erratically.

Revised 8-Apr-2017 to correct SPOUT problem symptoms wording

The PIP is a Hall Effect magnetic sensor that triggers the TFI and injectors. There is a shutter wheel alternately covers and uncovers a fixed magnet as it rotates. The change in the magnetic field triggers the sensor. They are often heat sensitive, increasing the failure rate as the temperature increases.

PIP Sensor functionality, testing and replacement:
The PIP is a Hall Effect magnetic sensor that triggers the TFI and injectors. There is a shutter wheel alternately covers and uncovers a fixed magnet as it rotates. The change in the magnetic field triggers the sensor. A failing PIP sensor will often set code 14 in the computer. They are often heat sensitive, increasing the failure rate as the temperature increases.

Some simple checks to do before replacing the PIP sensor or distributor:
You will need a Multimeter or DVM with good batteries: test or replace them before you get started.. You may also need some extra 16-18 gauge wire to extend the length of the meter’s test leads.
Visual check first: look for chaffed or damaged wiring and loose connector pins in the TFI harness connector.
Check the IDM wiring – dark green/yellow wire from the TFI module to pin 4 on the computer. There is a 22K Ohm resistor in the wiring between the TFI and the computer. Use an ohmmeter to measure the wire resistance from the TFI to the computer. You should see 22,000 ohms +/- 10%.
Check the PIP wiring - dark blue from the TFI module to pin 56 on the computer. Use an ohmmeter to measure the wire resistance from the TFI to the computer. You should see 0.2-1.5 ohms.
Check the SPOUT wiring – yellow/lt green from the TFI module to pin 36 on the computer. Use an ohmmeter to measure the wire resistance from the TFI to the computer. You should see 0.2-1.5 ohms.
Check the black/orange wire from the TFI module to pin 16 on the computer. Use an ohmmeter to measure the wire resistance from the TFI to the computer. You should see 0.2-1.5 ohms.
Check the red/green wire; it should have a steady 12-13 volts with the ignition switch on and the engine not running.
Check the red/blue wire; it should have a steady 12-13 volts with the ignition switch in Start and the engine not running. Watch out for the fan blades when you do this test, since the engine will be cranking.
If you do not find any chaffed or broken wires, high resistance connections or loose pins in the wiring harness, replace the PIP sensor or the distributor.

The PIP sensor is mounted in the bottom of the distributor under the shutter wheel. In stock Ford distributors, you have to press the gear off the distributor shaft to get access to it to replace it. Most guys just end up replacing the distributor with a reman unit for about $75 exchange

PIP problems & diagnostic info
Spark with the SPOUT out, but not with the SPOUT in suggests a PIP problem. The PIP signal level needs to be above 6.5 volts to trigger the computer to pulse the fuel injectors, but only needs to be 5.75 volts to trigger the TFI module. Hence with a weak PIP signal, and the SPOUT in, you could get spark but no injector pulse. You will need an oscilloscope or graphing DVM to measure the output voltage since it is not a straight DC voltage.

See http://www.wellsmfgcorp.com/pdf/counterp_v8_i2_2004.pdf and http://www.wellsmfgcorp.com/pdf/counterp_v8_i3_2004.pdf for verification of this little detail from Wells, a manufacturer of TFI modules and ignition system products.

Was hoping for a window, but Its been raining all day, Picked up a solid scanner anyway (overdue) and will post codes and PIP test results in the morning if this lets up. Thanks again brother..

 

[90sickfox]

My 1989 gt 5 speed ( so called ultralight ) had an A9M computer. I still have it and I have a break out box for testing it. Could compare readings. I can get all the info you need on it.

I forget things a bunch so I may need some reminding to get to it.

 

[Shooter50]

Dump codes sticky

Look at the top of the 5.0 Tech forum where the sticky threads are posted. One of them is how to dump the computer codes. Codes may be present even if the CEL (Check Engine Light) isn’t on. You don’t need a code reader or scanner – all you need is a paper clip, or if your lady friend has a hair pin, that will do the job.
I highly suggest that you read it and follow the instructions to dump the codes. http://www.stangnet.com/mustang-forums/threads/how-to-pull-codes-from-eec4.889006/

No pulse from the injectors is probably a PIP problem, may show a code 14 dumping the codes. Code 14 - Ignition pickup (PIP) was erratic – the Hall Effect sensor in the distributor is failing. Bad sensor, bad wiring, dirty contacts. Factory tach will sometimes read erratically.

Revised 8-Apr-2017 to correct SPOUT problem symptoms wording

The PIP is a Hall Effect magnetic sensor that triggers the TFI and injectors. There is a shutter wheel alternately covers and uncovers a fixed magnet as it rotates. The change in the magnetic field triggers the sensor. They are often heat sensitive, increasing the failure rate as the temperature increases.

PIP Sensor functionality, testing and replacement:
The PIP is a Hall Effect magnetic sensor that triggers the TFI and injectors. There is a shutter wheel alternately covers and uncovers a fixed magnet as it rotates. The change in the magnetic field triggers the sensor. A failing PIP sensor will often set code 14 in the computer. They are often heat sensitive, increasing the failure rate as the temperature increases.

Some simple checks to do before replacing the PIP sensor or distributor:
You will need a Multimeter or DVM with good batteries: test or replace them before you get started.. You may also need some extra 16-18 gauge wire to extend the length of the meter’s test leads.
Visual check first: look for chaffed or damaged wiring and loose connector pins in the TFI harness connector.
Check the IDM wiring – dark green/yellow wire from the TFI module to pin 4 on the computer. There is a 22K Ohm resistor in the wiring between the TFI and the computer. Use an ohmmeter to measure the wire resistance from the TFI to the computer. You should see 22,000 ohms +/- 10%.
Check the PIP wiring - dark blue from the TFI module to pin 56 on the computer. Use an ohmmeter to measure the wire resistance from the TFI to the computer. You should see 0.2-1.5 ohms.
Check the SPOUT wiring – yellow/lt green from the TFI module to pin 36 on the computer. Use an ohmmeter to measure the wire resistance from the TFI to the computer. You should see 0.2-1.5 ohms.
Check the black/orange wire from the TFI module to pin 16 on the computer. Use an ohmmeter to measure the wire resistance from the TFI to the computer. You should see 0.2-1.5 ohms.
Check the red/green wire; it should have a steady 12-13 volts with the ignition switch on and the engine not running.
Check the red/blue wire; it should have a steady 12-13 volts with the ignition switch in Start and the engine not running. Watch out for the fan blades when you do this test, since the engine will be cranking.
If you do not find any chaffed or broken wires, high resistance connections or loose pins in the wiring harness, replace the PIP sensor or the distributor.

The PIP sensor is mounted in the bottom of the distributor under the shutter wheel. In stock Ford distributors, you have to press the gear off the distributor shaft to get access to it to replace it. Most guys just end up replacing the distributor with a reman unit for about $75 exchange

PIP problems & diagnostic info
Spark with the SPOUT out, but not with the SPOUT in suggests a PIP problem. The PIP signal level needs to be above 6.5 volts to trigger the computer to pulse the fuel injectors, but only needs to be 5.75 volts to trigger the TFI module. Hence with a weak PIP signal, and the SPOUT in, you could get spark but no injector pulse. You will need an oscilloscope or graphing DVM to measure the output voltage since it is not a straight DC voltage.

See http://www.wellsmfgcorp.com/pdf/counterp_v8_i2_2004.pdf and http://www.wellsmfgcorp.com/pdf/counterp_v8_i3_2004.pdf for verification of this little detail from Wells, a manufacturer of TFI modules and ignition system products.

Soo, I just had a break in the weather.. I had tried the old jumper code trick and was getting no check engine light flashing. So I had figued the was either no codes or the bulb might be burnt out. So I bought a scanner, and its not linking up.. Also discovered that if i wait a good 20 seconds (between ign on) I can now hear the fuel pump finally run on its own. Curiously that was not the case before, might have fixed that with cap repair. Going back out to run the pip tests.. If you have any Ideas in the mean time I appreciate your help.. Maybe this narrows it down.