New pump Now im pissed.

have you replaced the fuel filter.

did you change the eec relay?? also have you tried jumpering power to the pump side of the inertia switch if the pump does not come on check your fuel pump ground at the plug by the tank, just ring the ground wirle for resistance. good luck I chased a fuel pump problem for months. I finally changed the eec relay and re connected the metal strap from the filler area back to the tank and it has worked ever since. chris

Back to the checklist...

Fuel Pump Troubleshooting for 87-90 Mustangs

Clue – listen for the fuel pump to prime when you first turn the ignition switch on. It should run for 5-20 seconds and shut off. To trick the fuel pump into running, find the ECC test connector and jump the connector in the lower RH corner to ground. See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html for a description of the test connector. 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. A tire pressure gauge can also be used if you have one - look for 37-40 PSI. Beware of fire hazard when you do this.

No fuel pressure, possible failed items in order of their probability:
A.) Tripped inertia switch – press reset button on the inertia switch. The 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.
C.) Clogged fuel filter
D.) Failed fuel pump
E.) Blown fuse link in wiring harness.
F.) Fuel pressure regulator failed. Remove vacuum line from regulator and inspect for fuel escaping while pump is running.

The electrical circuit for the fuel pump has two paths, a control path and a power path.

The control path consists of the inertia switch, the computer, and the fuel pump relay coil. It turns the fuel pump relay on or off under computer control. The switched power (red wire) from the ECC relay goes to the inertia switch (red/black wire) then from the inertia switch to the relay coil and then from the relay coil to the computer (tan/ Lt green wire). The computer provides the ground path to complete the circuit. This ground causes the relay coil to energize and close the contacts for the power path. Keep in mind that you can have voltage to all the right places, but the computer must provide a ground. If there is no ground, the relay will not close the power contacts.

The power path picks up from a fuse link near the starter relay. Fuse links are like fuses, except they are pieces of wire and are made right into the wiring harness. The feed wire from the fuse link (orange/ light blue wire) goes to the fuel pump relay contacts. When the contacts close because the relay energizes, the power flows through the contacts to the fuel pump (light pink/black wire). The fuel pump has a black wire that supplies the ground to complete the circuit.

Remember that the computer does not source any power to actuators, relays or injectors, but 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.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

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

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif

Now that you have the theory of how it works, it’s time to go digging.

Look for 12 volts at the Orange/Lt. Blue wire (power source for fuel pump relay). No voltage or low voltage, bad fuse link, bad wiring, bad ignition switch or ignition switch wiring or connections. There is a mystery connector somewhere under the driver’s side kick panel, between the fuel pump relay and the fuse link.

Turn on the key and jumper the fuel pump test connector to ground as previously described. Look for 12 volts at the Light Pink/Black wire (relay controlled power for the fuel pump). No voltage there means that the relay has failed, or there is a broken wire in the relay control circuit.

Check the Red/black wire, it should have 12 volts. No 12 volts there, either the inertia switch is open or has no power to it. Check both sides of the inertia switch: there should be power on the Red wire and Red/Black wire. Power on the Red wire and not on the Red/Black wire means the inertia switch is open.

The Tan/Lt Green wire provides a ground path for the relay power. With the test connector jumpered to ground, there should be less than .75 volts. Use a test lamp with one side connected to battery power and the other side to the Tan/Lt Green wire. The test light should glow brightly. No glow and you have a broken wire or bad connection between the test connector and the relay. To test the wiring from the computer, remove the passenger side kick panel and disconnect the computer connector. It has a 10 MM bolt that holds it in place. With the test lamp connected to power, jumper pin 22 to ground and the test lamp should glow. No glow and the wiring between the computer and the fuel pump relay is bad.

If all of the checks have worked OK to this point, then the computer is bad. The computers are very reliable and not prone to failure unless there has been significant electrical trauma to the car. Things like lightning strikes and putting the battery in backwards or connecting jumper cables backwards are about the only thing that kills the computer.

Hav you checked the fusable link up near the starter solenoid? I had that go out and I didn't even know it existed. I tried replacing everything as well and that was the problem.

RsStanG1987 said:

I did not connet that strap from the filler yet.. Is it possible that is my problem?

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The stap on the filler is to pass any static electricty to chassis ground. Leave it loose and you risk a static electric spark while fueling your car.

Go back and do the checklist first, then start here.

The pump power ground is a black wire in the same harness as the pump power. Make sure the black wire is securely connected to ground.

If you have an ohmmeter, disconnect the power & ground leads at the quick connector. Measure the resistance of the pump side wiring between the lt pink/black wire and the black wire. You should see less than 2 ohms. More than that is some bad wiring/bad connections on the pump.

RsStanG1987 said:

Well I heard from a friend thatv the EEC relay could be bad. Im gonna change that relay then go from there.

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Not to be rude, but tossing parts at it costs money and wastes time. JR is trying to help you and his flow-chart-like list systematically troubleshoots the system.

30 seconds with your meter would tell you what you are missing at the FP relay or at the FP connector. As for the EEC relay, when you turn the key on do you hear any sensors or solenoids click? If so, the EEC relay is likely fine. I really would follow JR's list; paying specific attention to the values you read at the FP relay socket is important (that socket is like a 4 way stop in the road and gives you a direction to pursue).

Good luck.

RsStanG1987 said:

I know what your saying its just the fact that i dont have a test light and need to get the car going asap. I dont think that any other sensors are clicking or making noise either now that i think about it. Im gonna go outside and double check. I know i know trouble shoot.

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Harbor Freight puts test lights on sale for 99 cents all the time. They also put DMM's on sale for 4 bucks. 5 bucks very well spent.

HISSIN50 said:

Harbor Freight puts test lights on sale for 99 cents all the time. They also put DMM's on sale for 4 bucks. 5 bucks very well spent.

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do you really want a 99 cent test light? and a 4 dollar muti meter sounds like a piece of poo. buy good tools.

a .99 cent test light will work wonders and save head aches and time if you dont even have a test light. All he is doing is testing for power, whats wrong with a sihtty test light for that?

86bluecobra said:

do you really want a 99 cent test light? and a 4 dollar muti meter sounds like a piece of poo. buy good tools.

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I have good test lights and good meters, as well as the cheap stuff. I use the cheap stuff day in and day out. As you should with any meter or light, you bench test it before use. And those cheapies work very well for me. A test light is so simple, there is no need for a good one for most of us (and the price is right if you break it).
Inexpensive DMM's are a relatively simple item, and most dont know how to use all the functions on a cheapie, let alone a more expensive unit. I choose to pick where I spend more money on a quality tool and where I can use something which will net the same results for a cheaper price.

Bottom line is that a cheap tool will help RS out more than nothing at all.

RsStanG1987 said:

Where the hell is harbor freight?

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Try Harborfreight.com . I think they have a store locator. If not, a test light from the parts store is under 5 bucks (I think). Just dont use a test light on computer controlled circuits.

I applaud your desire to get the proper diagnostic tools to evaluate the problem. The first time you troubleshoot a particular part or system and dont have to buy that part to see if it fixes the issue, you will have paid for the test light and/or meter.

Good luck.

RsStanG1987 said:

Where the hell is harbor freight?

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In Orlando, it is in the shopping center on the corner of 436 & Howel Branch Rd. There is a Burger King on the corner across from it. They were having a sale on the cheap DVM's - under $3 if I remember correctly.

If you go on a sunny Saturday, you can watch them race RC cars in one corner of the parking lot :

Yes, that Harbor Freight tool store is godly JR. I'm there like every week walking around like a kid in a candy store.

Another good thing to check with the DMM is to check for 12v at the quick disconnect coming from the car right by the rear bumper. I think you can also check 12v at the bottom rear spot at the trouble code hook up. Mine says 12v anyways.