Fuel gauge pegged to the top, car shuts off

Shawn_Mc

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Oct 1, 2021
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A bizarre issue. I've owned this 1989 5.0 Fox body convertible since brand new. It's got 199K miles on it. All mine. Car still gets 22mph on the original 5.0 that's never had a valve cover off and doesn't burn any more oil now than it did when new (which was a lot in my opinion). The only things Ive had to fix on this car was an alternator, a water pump and I rebuilt the transmission.

Recently the fuel gauge started pegging toward the top when I topped off the tank. No biggie. Then I ended up with a no start issue. I had spark, had to be fuel. I replaced the fuel pump and the sender (remember the gauge issue) while I had the tank out. Car fired right up, ran great for 20 minutes. Then another no start. Close to 20 years ago I had to replace the ignition module because it died. So I did that. Still no start (mind you, I'm in the parking lot of the Autozone, no meter, no tools etc). Still no start, got it home.
I'm checking for fuel pressure again, none. Drop the tank again, check the fuel pump, It runs. Check the relay, It's working. Put it all back, it fires up. Runs great. For 20 minutes.
When it dies, it literally feels like the ignition is being cut, not like it's running out of fuel. Then I noticed that when it cuts out, the Fuel gauge is not just pegged, the needle has disappeared into the dash. Then it'll come back. when the gauge is working, the car runs perfect, but when the gauge acts up. its a wild card.

Another strange thing about the gauges, the volt meter shows low volts, but running, at the battery, 14.5v on my meter (BluePoint)

Could that fuel slosh board be shorting the entire ignition power circuit? I cant find a decent schematic for this car anywhere. I'm also (was) an ASE certified mechanic, so it's not like Im short on experience. But this intermittent stuff...OMG... Is there a bad Cap on that slosh board that's ruining my day?
 
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revhead347

Apparently my ex-husband made that mistake.
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That sounds like a nightmare. Pull the slosh board and see if it fixes it.

Kurt
 

KRUISR

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When you get the no start condition, if you try to restart can you hear the fuel pump re-prime the system before cranking?

I chased a random no start (no fuel pump priming) problem. I replaced the fuel pump relay a couple times and would still get random no starts. It turned out to be the plug connection in the driver kick panel where the power for the fuel pump goes through.
 

Shawn_Mc

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When you get the no start condition, if you try to restart can you hear the fuel pump re-prime the system before cranking?

I chased a random no start (no fuel pump priming) problem. I replaced the fuel pump relay a couple times and would still get random no starts. It turned out to be the plug connection in the driver kick panel where the power for the fuel pump goes through.
I can usually hear it. I pulled the seat to diagnose the relay too. But I'll check that plug. But since the last time I had the tank out, and messed with the pump relay, it'll always start. When it dies, it's like a power shut of is being kicked on and off. But dont get any lights, I dont get a check engine until the engine actually stops.
Where could I get one of those Slosh modules? Because all this weirdness started when I noticed the volt guage reading low, then the fuel gauge reading way high when the tank was full. Im wondering if all this goes away If I unplug the sender entirely at the tank, which would be a pain in the ass, just to try...I hate intermittent stuff.
 

manicmechanic007

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The slosh module sure should have nothing to do with a no start condition
However the gauge and pump wiring go thru the troublesome connector at the top of the pump module assembly
A short there could cause both problems
I have a slosh module in my garage but you should have no trouble finding several at the junkyard cheap
I'm with Kurt, pull it out and try it again
 

Shawn_Mc

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The slosh module sure should have nothing to do with a no start condition
However the gauge and pump wiring go thru the troublesome connector at the top of the pump module assembly
A short there could cause both problems
I have a slosh module in my garage but you should have no trouble finding several at the junkyard cheap
I'm with Kurt, pull it out and try it again
I found a new reproduction module, I'll install that and see how it goes. The no start seems to have gone away for now. But as soon as I drive over a bumpy road (car is lowered a little too) it'll cut out randomly. I'll look for that plug behind the kick panel. Once I get it back to being a no brainer reliable again, Ive already got new interior here, waiting to be installed. Ive got all the hard and wear parts for the AC to be replaced too. It just leaks at every connection. This was my first new car in Oct of 1988. And the way I drove that car, as a young guy, dont let anyone ever tell you the 302 wasnt pretty tough.
 
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manicmechanic007

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It probably needs a gauge and has an additional no start or intermittent dying problem
Replaced a few gauges over the years at the dealer
Pull the cluster put a dvom on the fuel sender wires and road test or interrogate
If an over bumps issue inspect the harness real good everywhere
They made us give it the "wiggle test"
Interrogate the harness (means slap it around pull on it yank it try to get it to fail while you are testing)
You can drive the car to denver with the cluster out
Make sure it is not your TFI module coil or stator build a test module
Tape a fuel pressure gauge to the windshield and test drive with test TFI installed
 

Bree

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Mine acted like that once. Is it throwing any codes? If not, could be the main computer. I had mine rebuilt through Auto Zone for about $200
 

Shawn_Mc

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Id love to find a schematic for the instrument cluster. Ive solved a couple really weird issues with this car that were electrical. My oil pressure gauge jumps all over hell. It has since new. Id take it in, they'd replace the sender, it'd be fine for a month...start doing the exact same thing again. When I was in Tech school, I found a decent schematic and noticed the 12v source for the oil pressure and the water temp were the same leg. The water temp sender was erratic, but the gauge didn't react, the oil pressure gauge would, It was acting like a capacitor and the spikes would impact the oil pressure gauge. I changed the temp sender and the oil pressure gauge stabilized.
I got the new slosh board, I'll get it in there and check all the connections and things.
When the car is running, it runs great. The alternator is brand new. I changed that when I noticed the low voltage on the gauge. I should have put the DVOM on it and checked before. The new alternator shows exactly the same as the old one on the OEM gauge. But the Meter at the battery shows 14.5V while running. And while the OEM gauge drops when I turn on the AC to full and the headlights at the same time, the measured voltage at the battery doesn't. Which sounds more like a bad connection somewhere...and there's that need for decent schematic again. When I was at school almost 20 years ago, I had access to the Ford schematics. Ya get spoiled quick with real information.
 
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Mustang5L5

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Id love to find a schematic for the instrument cluster.

Ask and ye shall receive

Oil pressure and fuel Guage are both tied into the slosh module for power along with the fasten seat belts light
57A53AD5-B9A5-4CE0-915C-725FEB5BE2C4.jpeg
0E6B97E0-9038-47A3-9ADA-A5FEA0D61856.jpeg
88F217C1-3975-4037-A840-65E27423CC90.jpeg
 
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Shawn_Mc

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Ask and ye shall receive

Oil pressure and fuel Guage are both tied into the slosh module for power along with the fasten seat belts light
57A53AD5-B9A5-4CE0-915C-725FEB5BE2C4.jpeg
0E6B97E0-9038-47A3-9ADA-A5FEA0D61856.jpeg
88F217C1-3975-4037-A840-65E27423CC90.jpeg
Is that schematic for an 89'? Reason I ask, it has connections for monitors that I dont have.

Who published that schematic? What book. I have seen anything that detailed since I saw the actual Ford detailed schematics in school.

Id love to get my hands on a version of that specifically for my car. 1989 5.0 LX Convertible manual car.

The only question I have about that particular drawing is, are the diodes on the fuel gauge slosh module on the board, or in the lines? It'd make more sense if they were on the board. But you know...engineers happen...
 

Mustang5L5

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Is that schematic for an 89'? Reason I ask, it has connections for monitors that I dont have.

Who published that schematic? What book. I have seen anything that detailed since I saw the actual Ford detailed schematics in school.

Id love to get my hands on a version of that specifically for my car. 1989 5.0 LX Convertible manual car.

The only question I have about that particular drawing is, are the diodes on the fuel gauge slosh module on the board, or in the lines? It'd make more sense if they were on the board. But you know...engineers happen...

It’s an ‘89 EVTM. The extra lights are the warning pod that comes on the GT only (or you can add them to the LX)



I have a spare cluster I can take a pic of to show where the diodes are.
 
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Shawn_Mc

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It’s an ‘89 EVTM. The extra lights are the warning pod that comes on the GT only (or you can add them to the LX)



I have a spare cluster I can take a pic of to show where the diodes are.
Man, I bought that manual and the body/chassis/electrical too. And the same for my Dodge. I wish I'd seen those years ago. Ive been working on motorcycles for the last couple decades. Those are published by Helms.

Thanks a bunch. I found a new repro slosh module that's actually much better than the OEM unit. I'll swap that in next week and check some connections and look for harness issues.

Thanks again!!
 
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Mustang5L5

Put lubricant all over the balls
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So...... Just asking for a friend.......where'd ya get da repro module, or is it a secret?
You know in case 'google' and all :shrug:

Google knows it all

 
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jrichker

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Fuel Quantity gauge troubleshooting 87-93 Mustangs

Revised 8-Apr-2017 to add warning about non-interchangeable fuel tank senders between 79-86 and 87-93 Mustangs.

54945


The red/yellow wire (power supply to gauge & sender) should have 12 volts when the ignition is in the start or Run position.

Troubleshooting the gauge and sender circuit:
Since the sender uses a variable resistor, sum the resistor values of 22 Ohms (empty value) & 145 Ohms (full value). That gets you 167, which you divide by 2: that gets you 83.5. So in theory, 83.5 ohms is 1/2 full. A trip to Radio Shack for the closest combination of resistors to make 83.5 ohms gets you one 68 Ohm (Catalog #: 271-1106) + one 15 Ohm (Catalog #: 271-1102) for a total of 83 Ohms at the cost of $2 plus tax. Wire the resistors in series to make a resistor pack and cover it with heat shrink tubing or electrical tape. The 83 Ohms is close enough to the 83.5 Ohm figure that it shouldn't matter. Disconnect the electrical connector shown in the diagram for the tank sender unit. Connect one end of the resistor pack to the yellow/white wire on the body side fuel sender electrical connector and the other end of the resistor pack to ground. Make sure nothing is touching that isn't supposed to and turn the ignition switch to Run. If I am correct, the fuel gauge will read 1/2 full, or very close to it. If it does not, then the odds are that the gauge or anti-slosh unit are bad.

How and why the test works…
Most of the fuel gauge failures give a stuck on full or stuck on empty as a problem symptom. Using a resistor combination that mimics 1/2 tank allows you to decide if the gauge and anti-slosh module are the problem source.

If the gauge reads about 1/2 tank with the resistor combination, that points to the sender as being the culprit.

If the gauge reads full or empty with the resistor pack in place of the sender, then the gauge or anti-slosh module is at fault.

Fuel gauge sender testing and replacement
The next steps require dropping the fuel tank and removal of the fuel level sender. Here are some useful tips...

I have done the tank removal three times, and the main issues are getting the car up on jack stands and getting the gas out of the tank. DO NOT try to do this job without jack stands. Becoming a pancake is not part of the repair process.

Pumping out the old gas:
If the old pump still works, you can use it to pump the tank out.
1.) Separate the pressure line (the one with the Schrader valve on it) using the fuel line tools.
Look in the A/C repair section for the fuel line tools. They look like little plastic top hats. You will need the 1/2" & 5/8" ones. The hat shaped section goes on facing the large part of the coupling. Then you press hard on the brim until it forces the sleeve into the coupling and releases the spring. You may need someone to pull on the line while you press on the coupling.
61yoVRLxcXL._SL1350_.jpg


OR

Twmjj23EpRXMFfHYVG6hYEK53GOKCWWvYG9-LefxImTo50cmW1.jpg


View: https://www.youtube.com/watch?v=vRTjYAxvaCs

Use a piece of garden hose to run from the pressure line to your bucket or gas can. Make sure it is as leak proof as you can make it. Fire and explosion are not part of the repair process...

2.) Jumper the fuel pump test point to ground.

attachments\68357\


Turn the ignition switch to the Run position. the fuel pump will pump the tank almost dry unless the battery runs down first.

Some 5 gallon paint pails lined with garbage bags are good to hold the gas. The garbage bags provide a clean liner for the pails and keep the loose trash out of the gas so you can reuse it. If you decide to use a siphon, a piece of 1/2" garden hose stuck down the filler neck will siphon all but a gallon or so of the gas.

Remove the filler neck bolts and put them in a zip bag. Disconnect the supply & return lines by removing the plastic clips from the metal tubing. If you damage the clips, you can get new ones form the auto part store for just a few dollars. I have used tie-wraps, but that is not the best choice. Then you remove the two 9/16" nuts that hold the T bolts to the straps. Put the nuts in the zip bag with the filler bolts. Pull the plastic shield down and away from the tank. Once the tank drops a little bit you can disconnect the wiring for the pump & fuel quantity sender.

The fuel gauge sender assembly comes out by removing a large metal ring that unscrews from the tank. There is a separate mounting/access plate for the fuel pump and fuel gage. You are supposed to use a brass punch to tap on the ring so that you don't make sparks. Look closely at the rubber O ring gasket when you remove the fuel gauge sender.
When you install the metal ring that holds the sender in place, watch out for the gasket O ring. Some RTV may be helpful if the ring is not in excellent condition.

The tank to filler pipe seal is a large rubber grommet. Inspect it for hardening, tears and damage. At $20 from the Ford dealer, it might be a good idea to replace it.

I used a floor jack to help lift the tank back in place. You may find that it is the only time you really can make good use of a helper.

All resistance measurements should be made with the power off.

Note from bstrd86 - 86 and older fuel tank sender units are 73 ohms empty, 8-12 ohms full. The 87-93 fuel tank senders are of 22 Ohms empty & 145 Ohms full. The two different groups of sensors are not interchangeable


The yellow/white wire will show a voltage that varies with the movement of the float on the sender unit. To test the sender, set your Ohmmeter or DVM on low Ohms. Then disconnect the sender and connect the Ohmmeter or DVM to the yellow/white and black wires from the sender unit. Move the float arm while watching the Ohmmeter or DVM. You should see the reading change from 22 to 145 ohms +/- 10%.

If the Ohmmeter or DVM resistance readings are way off, replace the tank sender unit.

Use extreme caution if you do the next step. Fumes from the gas tank can easily ignite and cause a fire or explosion.
With the sender unit out of the tank and connected to the body wiring harness, turn the ignition switch to the Run position. Move the float arm and the fuel gauge indicator should move. If you are very careful, you can use a pair of safety pins inserted in the connector for the yellow/white and black wires to measure the voltage as you move the float arm. The voltage will change, but I have no specs for what it should be.
Do not short the safety pins together or to ground. If you do, you may damage the anti-slosh module or create a spark. A spark with the fuel tank open could cause a fire or an explosion.

If the voltage does not change and the tanks sender passed the resistance tests, the anti-slosh module or gauge is bad.


The 87-89 module is shown below.
[
Slosh_Module_Original.jpg


This is what the 90-93 module looks like.
lrs-10849_1937.jpg


LRS has the 90-93 module as a standard catalog item, cost is about $160



Inexpensive anti-slosh module repair - should work on 87-93 anti-slosh modules

Copied from DrBob

I worked on an 88 Mustang today that had similar symptoms. Short version, I took the “anti slosh module” off of the back of the instrument cluster and replaced the electrolytic capacitor. Fixed it for $1.39 with a part from Radio Shack.

In an attempt to help other folks, here’s the long version.
Remove the “anti slosh module” located on the back of the instrument cluster. There was a single Torx screw holding mine to the cluster.

Find the electrolytic capacitor. It will be the largest, 2 wire component on the board. The capacitor may have a red or blue plastic wrapper on it. Mine was red.

The wrapper should have printing on it. Look for printing that looks something like this:
100uF+25V

The “100uF” tells you this is a 100 micro Farad capacitor. The “+25V” tells you the capacitor is rated for 25 Volts. Yours may be different. You may use a higher voltage part but don't use a lower rated voltage part. If you use a lower voltage part the capacitor might open later on down the road or it could be as bad as catching fire.

If you can’t find the printing you’ll need to remove the part. You have to anyway so nothing wasted. However pay close attention to the way the capacitor is oriented on the board.

One end of the capacitor will be bare metal with a wire sticking out. The other end should have some sort of insulation over it with a wire sticking out. The bare metal end is the negative end while the insulated end is the positive end. Pay attention to which end is connected to which hole on the board.

Get a replacement part. I got mine at Radio Shack, $1.39. Here’s the info:
100µF 35V 20% Axial-Lead Electrolytic Capacitor
Model: 272-1016 | Catalog #: 272-1016

See www.Digikey.com for better capacitors – these are rated for automotive use and 105° C temp which is needed to survive the hot environment found in automotive electrical circuits.
P/N 4215PHCT-ND $2.10
OR
P/N 4201PHCT-ND $2.59

Fuel tank sender unit:

Be sure to get the lock ring and a new seal if you order the tank sender unit.



For the No Start condition, use the checklist below...
It’s Decision Tree time:

No spark = go to step #1 & 2.
Good spark - what is a good spark can be a subjective judgment. If you have any doubts, borrow a known good coil from another pre 1996 Ford.
If you do have good spark = go to step # 3

Engine fires off and then dies = go to step # 4
Make sure that you have fuel pressure when the engine fires off. Leave the fuel pressure gauge connected while testing so that you can observe what the fuel pressure is doing.

Fuel pressure OK while cranking
Go to step # 5
Be sure to use a noid light to see if the injectors are pulsing. Use the most accessible fuel injector connector for the noid test.

Noid light pulses and fuel pressure is good.
Go to step #6


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 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 27-Oct-2020 to add need for good PIP signal to keep the fuel pump running after initial 1-3 second prime.

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, Crane, or other ignition box if present - Bypass it and return to stock configuration if possible. Do this as a temporary measure to eliminate it as a possible problem source.
B.) PIP sensor in distributor. The PIP sensor supplies the timing pulse to trigger the TFI, fuel pump, and injectors. The computer looks for a continuous stream of PIP pulses to keep the fuel pump constantly running. 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.
See the Ignition switch wiring diagram for more information on the ignition wiring fuse link because it is the next thing to be tested. You will need a Multimeter or DVM and know how to use the Ohms function to check continuity between the red/green wire on the ignition coil and the red/green wire on the ignition switch. Make sure that the ignition switch is in the off position when you do the check. You should see less than 1 Ω (Ohm) between the red/green wire on the coil and the red/green wire on the ignition switch. More than 1 Ω means that the fuse link may have blown open and needs to be replaced. If you get 1 Ω or less means the fuse link is OK and the ignition switch is bad.

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.

attachments\68357


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.



64326




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.
attachments\610738


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.
 
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Shawn_Mc

Member
Oct 1, 2021
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Anahiem
Google knows it all


National Parts Depot, Ocala Florida.
Had it in stock. It wasn't cheap, but it wasn't an arm and leg either. $155 to the door.
 

Shawn_Mc

Member
Oct 1, 2021
31
8
18
59
Anahiem
Fuel gauge is working correctly now. I found the volt meter connections on the back were a tad loose, I put a 1/3rd of a turn on them, cleaned some contacts and that gauge reads exactly the same as my DVOM. Even the oil pressure gauge is more stable.
This is kind of a weird thing, the engine cutting out seems to be getting less and less. As it warms up, it disappears completely. Im going to have to drive this thing until it fails completely.
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
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polk county florida
Yeah, this is a great idea :nice:

Im going to have to drive this thing until it fails completely.
and when it dies in the middle of an intersection or in traffic where stupid people will do stupid things while on their social media devices (it's not a phone anymore, it's a companion like a therapy animal) like smash into you.
but I digress,