Fuel Pump questions

Make sure the ground is hooked up by the battery. May have forgot to hook it back up when hiding the wires..

Did you try reseting the inertia switch yet?

lxsteed said:

The battery is in the trunk, so I know thats still hooked up.

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Not the battery ground itself, but the ground for the EEC harness. The ground will have a plug on it about 6-8 inches fron the ground loop, if it's still there. If not just cut the plug off and ground it to the body..

if u got an electric fuel pump, those &*$%ing things will go out instantly, so if all the switchs like one under the seat and in the trunk are fine, ur pump may have just stopped working.

check your fusable links and fuses blus the relay

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.

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 or connections. There is a mystery connector (one I haven’t found) under the dash somewhere, 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 and only if you have followed the test procedure to this point and still haven’t found the problem, the computer is suspect.

OK i read through the post but i still have a question. I'm trying to get my motor started for the first time. It'll start but shut down right away.. The fuel pump primes but only when I have it in the start position, not in the accessory like it used to. I know this because I turned the key without depressing the clutch and heard it. What could be going wrong here? Someone please help, I've been waiting 6 months to get the motor back in this thing. Thanks

it is not supposed to prime when in acc. position anyway

lxsteed said:

Ok, need more help. I figured out there was a wire that I grounded, that needed to be power, switched that, now I have 12V all the time to the Green/yellow wire, and 12V ignition on power at the tan/light green wire. But no power from the pink/black wire that goes to the fuel pump.

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Ok, this is probably your problem b/c this other guy and myself had this problem too. Green/Yellow should be a constant 12v, Pink/Black wire is 12v for 2 seconds with the ignition "on" position, Red/Black wire should be constant 12v with ignition "on" position, and Tan/light green wire is ground. Make sure the grounded wire is on the tan/lt.green wire. Ok now, check the EEC relay located above the computer behind the passenger kicker panel. If you have a/c in your car still, the blower fan assembly is going to be a bother. So I suggest removing the harness from computer first (10mm bolt), then remove the plastic hold-down bracket, then the computer. On the EEC relay, check the red wire with ignition "on", you should see 12v, if not run a wire from the red/lt.green wire from under the steering wheel to the EEC relay. This should solve your problem.

lxsteed said:

The Pink/Black wire should be 12 all the time while the key is on. That is the wire I have my toggle switch wired in to. Why would I have to do all that work if it worked before just fine?

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Thats what I said before I started on mine. All I know is that the EEC Relay triggers the Fuel Pump Relay. You won't get the full 12v.