Electrical Electrical Puzzles

BugsOli

15 Year Member
Jul 1, 2013
56
20
19
Belgium
Hi guys, after searching on the Internet and here, I could'nt find any answer hence this first post...

First, the background: bought a 1987 GT Convertible here in The Netherlands, one of the previous owner asked a shop to install an aftermarket alarm (yikes) with a integrated circuit-breaker and a remote control to open the doors.
One day, I take the car for a ride and BAM, no more battery (it was dead anyway) so I bought a brand new one and leave the car like that; 3 days after, want to take car and BAM, new battery totally drained!

Ok I think, maybe the alarm is draining the battery I tell myself, since when you remove the key the circuit-breaker kicks in and you have to use the remote to deactivate it.

So this winter, I've tackled to remove everything related to the alarm: the wires, the siren, the circuit-breaker, the trunk & hood detectors, etc. and found out what it is to have broken wires, especially on the ignition switch:
IMG_0921.JPG
IMG_0924.JPG
IMG_0929.JPG

After buying a new switch on NPD to get the proper wire size & connectors, I managed to rewire everything with Posi-Locks because I didn't want to put heat on heat shrinks due to the tight space under the steering column:
IMG_0967.JPG
IMG_0968.JPG

I've installed new battery cables (NEG & POS), cleaned the NEG post terminal next to the battery and reinstalled the battery (fully charged) only with the POS cable since I don't want to end-up with fried fuses (yet).

Now when I measure the resistance on the fuses panel, I get between 1.5 & 4.0 ohms on nearly every fuses except fuses #6, 11, 18 where I read 35 ohms.

For the fuse #11, I think it comes from the fact that the previous owner had installed an aftermarket amp with a 12-CD changer in the trunk and rewired everything from the radio to this installation so I've removed everything and I think I've forgot a ground somewhere.

Fuses #6 & 18 are bugging me, is it normal to have such a high resistance? The key is not on the ignition and only the POS battery side is wired.

Thanks,
Oliver
 
  • Sponsors (?)


PM me your email address and I will send you a complete Ford Factory 89 Mustang electrical diagram set. The zip file is 2.5 MB and is too big to fit through Stangnet's email gateway. The 89 and 87 body harness are pretty much the same. The EFI harness wiring harness is the major difference.

89 Mustang wiring diagrams zip package–

They are in a zip file format to reduce the size of the package. If you don't have Windows 7 or Windows 8, you’ll need WinZip or other Windows archive tool to extract them from the zip file.. See www.majorgeeks.com - Download Freeware and Shareware Computer Utilities for a free download.
The diagrams show the location area and the connectors are drawn to the same shape as those in the car.
You will need the Adobe Acrobat viewer which is also a free download – www.adobe.com/products/acrobat/readstep2.html - Adobe Reader download - All versions
 
Thanks J, I'll send you a PM.

Yesterday, I managed to restore some good resistance in my #18 fuse, but lost it on the #1, 4, 6, 8, 9 & 10 fuses!
I don't get what's missing, I've checked all the grounds and repaired the one above the RH headlamps which was frayed with a crimper and thermo insulation...

I've also removed the #11 fuse since my radio is missing and all the wires coming out of the factory amp were broken (I've cut them neatly and left as-is for now).

I'm getting tired of this stupid stuff... I have infinite resistance on the yellow wires at the ignition switch, could this be it? The battery is not wired at all
 
A little update: the car starts right away now but the idle is too low so the engine is dying if I don't push on the gas pedal so I'm going to check the TPS, clean the TB, MAF & IAC.
The only thing not working is the trunk release and the dash lights, all coming from fuse #6 I believe...
 
You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix. :D

It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 134,000 hits, which indicates it does help fix idle problems quickly and inexpensively.
 
Hello J, you are right, this check list is damn good and I've read thoroughly.
I've managed to get my idle perfect by cleaning the IAC & TB and I've verified my TPS which was set at 0.93 volts, so I changed the value to 0.98 volts and now it's idling perfectly!!!

Now I need to check my fuse #6 ;)

Last question: you say in the check list at point #8
8.) MAF meter on CAI system that needs clocking or protection from engine compartment air turbulence. A cone type filter located inside the engine compartment is almost sure to have surge problems due to the hot, turbulent airflow around it.
The problem is: I've bought the car with the Pro-M 77mm already in it (I've replaced the filter with a new K&N), a bullet type as you can see on this picture:
IMG_0135.JPG

Could this setup explain the "rocking chair" effect I experience at slow speed when the car is really hot? It's hard to explain this effect, it's like the car is going to stall then I depress the clutch and it's ok, etc.
 
Hello J, you are right, this check list is damn good and I've read thoroughly.
I've managed to get my idle perfect by cleaning the IAC & TB and I've verified my TPS which was set at 0.93 volts, so I changed the value to 0.98 volts and now it's idling perfectly!!!

Now I need to check my fuse #6 ;)

Last question: you say in the check list at point #8

The problem is: I've bought the car with the Pro-M 77mm already in it (I've replaced the filter with a new K&N), a bullet type as you can see on this picture:
IMG_0135.JPG

Could this setup explain the "rocking chair" effect I experience at slow speed when the car is really hot? It's hard to explain this effect, it's like the car is going to stall then I depress the clutch and it's ok, etc.
That is a possible cause. Also make sure that the NSS (Neutral Safety Switch) and Clutch switches are working correctly. They both affect the idle/stall conditions.
 
Thanks J, I'll have a look at that.
Here is another problem: yesterday I went for a really long drive (more than 100 miles) to go to work and I drove with the cruise control on all the time set at 65 mph (yes, nearly all electrical stuff is working now except my dash lights!).
The drive went smooth (all highway) but when I reached a traffic jam around 20 miles from my destination, I got a BIG problem: after having stopped in the traffic for 30 seconds, I drove off in 1st, then stomped on the gas when in 2nd gear, then passed to 3rd gear and then BAM, no more power, the RPM & speed gauges dropped to 0 but the engine was still turning and was still around 2500 RPM but the whole ignition stopped like that on the left lane (it's kinda stressful...).
I've managed to get to the emergency lane and stopped the car but could'nt start it again: the fuel pump was working and the engine was cranking but nothing could make it start.
Do you guys think it might be the ignition wire coming from the steering column?
 
When it won't start, run the checklist...

Cranks OK, but No Start Checklist for Fuel Injected Mustangs

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 your way down. Jumping around will possibly cause you to miss just what you need to see to find and fix the problem. Don’t skip any steps because the next step depends on the last step working correctly.


Revised 12-Dec-2011 to replace 10 pin salt & pepper connector graphic.

All text applies to all models unless stated otherwise.

Note: 94-95 specific changes are in red

1.) Remove push on connector (small red/blue wire) from starter solenoid and turn ignition switch to the Run position. Place car in neutral or Park and set the parking brake. Remove the coil wire from distributor & and hold it 3/8” away from the engine block. Jumper the screw to the big bolt on the starter solenoid that has the battery wire connected to it. You should get a nice fat blue spark.
Most of the items are electrical in nature, so a test light, or even better, a voltmeter, is helpful to be sure they have power to them.

No spark, possible failed items in order of their probability:
A.) MSD or Crane ignition box if so equipped
B.) PIP sensor in distributor. The PIP sensor supplies the timing pulse to trigger the TFI and injectors. A failing PIP sensor will sometimes let the engine start if the SPOUT is removed. See paragraph 5A – Using a noid light will tell if the PIP is working by flashing when the engine is cranking.
C.) TFI module: use a test light to check the TFI module. Place one lead of the test light on the red/green wire on the ignition coil connector and the other lead on the dark green/yellow wire on the ignition coil connector. If the TFI is working properly, the test light will flash when the engine is cranked using the ignition switch.
D.) Coil
E.) No EEC or computer power - EEC or computer relay failure
86-93 models only: EEC relay next to computer - look for 12 volts at the fuel injector red wires.
94-95 models only: EEC or PCM power relay in the constant control relay module. Look for 12 volts at the fuel injector red wires.
Both 86-93 and 94-95 models: No 12 volts with the ignition switch in the run position on the fuel injector red wires. The relay has failed or there is no power coming from the ignition switch. Make sure that there is 12 volts on the red/green wire on the coil before replacing the relay.
F.) No EEC or computer power - fuse or fuse link failure
86-93 models only: Fuse links in wiring harness - look for 12 volts at the fuel injector red wires. All the fuse links live in a bundle up near the starter solenoid. Look for a 20 gauge blue fuse link connected to 2 black/orange 14 gauge wires.
94-95 models only: 20 amp EEC fuse in the engine compartment fuse box. Look for 12 volts at the fuel injector red wires.
G.) Ignition switch - look for 12 volts at the ignition coil red/lt green wire. No 12 volts, blown fuse link or faulty ignition switch. Remove the plastic from around the ignition switch and look for 12 volts on the red/green wire on the ignition switch with it in the Run position. No 12 volts and the ignition switch is faulty. If 12 volts is present in the Run position at the ignition switch but not at the coil, then the fuse or fuse link is blown.
Note: fuses or fuse links blow for a reason. Don’t replace either a fuse or fuse link with one with a larger rating than stock. Doing so invites an electrical fire.
Ignition fuse links may be replaced with an inline fuse holder and 5 amp fuse for troubleshooting purposes.
94-95 models only: Check inside fuse panel for fuse #18 blown – 20 amp fuse
H.) Missing or loose computer power ground. The computer has its own dedicated power ground that comes off the ground pigtail on the battery ground wire. Due to it's proximity to the battery, it may become corroded by acid fumes from the battery.
In 86-90 model cars, it is a black cylinder about 2 1/2" long by 1" diameter with a black/lt green wire.
In 91-95 model cars it is a black cylinder about 2 1/2" long by 1" diameter with a black/white wire.
You'll find it up next to the starter solenoid where the wire goes into the wiring harness
I.) Computer. Don’t replace the computer just because you don’t understand how it works. Computers seldom fail, it usually is a sensor or wiring problem that causes the problems.
J.) Bad or missing secondary power ground. It is located between the back of the intake manifold and the driver's side firewall. It supplies ground for the alternator, A/C compressor clutch and other electrical accessories such as the gauges.
K.) Engine fires briefly, but dies immediately when the key is released to the Run position. Crank the engine & when it fires off, pull the small push on connector (red/blue wire) off the starter relay (Looks like it is stuck on a screw). Hold the switch in the crank position: if it continues to run there is a problem with either the ignition switch or TFI module. Check for 12 volts at the red/green wire on the coil with the switch in the Run position. Good 12 volts, then replace the TFI. No 12 volts, replace the ignition switch.

Wiring Diagrams:

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring Mustang FAQ - Engine Information Everyone should bookmark this site.

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

Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/91-93_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for 94-95 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/94-95_5.0_EEC_Wiring_Diagram.gif


AutoZone wiring diagrams: You can navigate to the diagrams yourself via Repair Info | AutoZone.com and select the car year, make, model and engine. That will enable you to bring up the wiring diagram for your particular car.

2.) Spark at coil wire, pull #1 plug wire off at the spark plug and check to see spark. No spark, possible failed items in order of their probability: [/b]
A.) Moisture inside distributor – remove cap, dry off & spray with WD40
B.) Distributor cap
C.) Rotor
D.) Spark Plug wires
E.) Coil weak or intermittent - you should see 3/8" fat blue spark with a good coil

3.) Spark at spark plug, but no start.
Next, get a can of starting fluid (ether) from your local auto parts store: costs a $1.30 or so. Then pull the air duct off at the throttle body elbow, open the throttle, and spray the ether in it. Reconnect the air duct and try to start the car. Do not try to start the car without reconnecting the air duct.

Two reasons:
1.) If it backfires, the chance for a serious fire is increased.
2.) On Mass Air cars, the computer needs to measure the MAF flow once the engine starts.
If it starts then, you have a fuel management issue. Continue the checklist with emphasis of fuel related items that follow. If it doesn’t, then it is a computer or timing issue: see Step 4.

Clue – listen for the fuel pump to prime when you first turn the ignition switch on. It should run for 2-4 seconds and shut off. To trick the fuel pump into running, find the EEC test connector and jump the connector in the Upper RH corner to ground. The EEC connector is near the wiper motor and LH hood hinge.

attachment.php


If the relay & inertia switch are OK, you will have power to the pump. Check fuel pressure – remove the cap from the Schrader valve behind the alternator and depress the core. Fuel should squirt out, catch it in a rag. Beware of fire hazard when you do this. In a pinch, you can use a tire pressure gauge to measure the fuel pressure. It may not be completely accurate, but you will have some clue as to how much pressure you have. If you have any doubts about having sufficient fuel flow/pressure, rent a fuel pressure test gauge from the auto parts store. That will tell you for sure if you have adequate fuel pressure.


4.) No fuel pressure, possible failed items in order of their probability:
A.) Tripped inertia switch – Coupe & hatch cars hide it under the plastic trim covering the driver's side taillight. Use the voltmeter or test light to make sure you have power to both sides of the switch
B.) Fuel pump power relay – located under the driver’s seat in most stangs built before 92. On 92 and later model cars it is located below the Mass Air Flow meter. Look for 12 volts at the Pink/Black wire on the fuel pump relay.
C.) Clogged fuel filter
D.) Failed fuel pump
E.) 86-90 models only: Blown fuse link in wiring harness. Look for 12 volts at the Orange/Lt Blue wire on the fuel pump relay.
91-93 models only Blown fuse link in wiring harness. Look for 12 volts at the Pink/Black wire on the fuel pump relay.
The fuse links for all model years 86-93 live in the wiring harness near the starter solenoid.
94-95 models only: 20 amp fuel pump fuse in the engine compartment fuse box. Look for 12 volts at the Dark green/yellow wire on the constant control relay module.
F.) Engine seem to load up on fuel and may have black smoke at the tailpipe. Fuel pressure regulator failed. Remove the vacuum line from the regulator and inspect for fuel escaping while the pump is running. If fuel is coming out the vacuum port, the regulator has failed. Check the regulator vacuum line for fuel too. Disconnect it from the engine and blow air though it. If you find gas, the regulator has failed.

5.) Fuel pressure OK, the injectors are not firing.
A.) The PIP sensor in the distributor tells the computer when to fire the injectors. A failing PIP sensor will sometimes let the engine start if the SPOUT is removed.
A noid light available from any auto parts store, is one way to test the injector circuit to see if the injectors are firing. The noid light plugs into the fuel injector harness in place of any easily accessible injector. Plug it in and try to start the engine: it will flash if the injector is firing.

I like to use an old injector with compressed air applied to the injector where the fuel rail would normally connect. I hook the whole thing up, apply compressed air to the injector and stick it in a paper cup of soapy water. When the engine cranks with the ignition switch on, if the injector fires, it makes bubbles. Cheap if you have the stuff laying around, and works good too.
B.) Pull an injector wire connector off and look for 12 volts on the red wire when the ignition switch is on.
C.) No power, then look for problems with the 10 pin connecter (salt & pepper shakers at the rear of the upper manifold).

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.


D.) No power and the 10 pin connections are good: look for broken wiring between the orange/black wire on the EEC relay and the red wire for the 10 pin connectors.
E.) TPS voltage exceeds 3.7 volts with the throttle closed. This will shut off the injectors, since the computer uses this strategy to clear a flooded engine. Use a DVM, a pair of safety pins, and probe the black/white and green wires to measure the TPS voltage.
On a 94-95 Mustang, probe the black/white and grey/white wires to measure the TPS voltage.
It should be .5-.1.0 volts with the key on, engine not running. Note that if the black/white wire (signal ground) has a bad connection, you will get some strange readings. Make a second measurement using the battery post as the ground to eliminate any ground problems. If the readings are different by more than 5%, you may have a high resistance condition in the black/white signal ground circuit.

6.) Spark & fuel pressure OK.
A.) Failed IAB or improperly set base idle (no airflow to start engine). Press the throttle ¼ way down and try to start the car. See the "Surging Idle Checklist for help with all your idle/stall problems.
B.) Failed computer (not very likely)
C.) Engine ignition or cam timing off: only likely if the engine has been worked on recently. If you removed the distributor, there is a good probability that you installed it 180 degrees out of time.
D.) Firing order off: HO & 351 use a different firing order from the non HO engines.
HO & 351W 1-3-7-2-6-5-4-8
Non HO 1-5-4-2-6-3-7-8
E.) No start when hot - Press the throttle to the floor & try starting it if you get this far. If it starts, replace the ECT.
F. ) Engine that has had the heads off or valves adjusted. Do a compression test to make sure the valves are not adjusted too tight. You should have a minimum of 90 PSI on a cold engine.