Fuel pump help needed NOW!!!

Cycle the key 10-20 times. That will build up the pressure in the system. The fuel pump cycles for 5-20 seconds only. it will not run longer than that, hence the need to cycle the key. If you are not building up pressure there is most likely a leak somewhere.

Since you just got the motor in the car, did you replasce the ground straps for the motor? If not that may be your problem. Since it is only coming on in the start position it sounds like a wiring problem. Check all your grounds to the computer and the harness under the hood. Also check and make sure that you have all the connectors plugged together that should be.

What year is your car, maybe I can email you some of the wiring diagrams that I have so that you can trace some of the wiring.

Are you sure it is not running in the Run position? The reason I ask is that you will not always hear the fuel pump from inside the car when it is running. Best thing to do to make sure is to tap into the wires with a test light or multimeter at the tank (there is a little connector back there that'll make this easy). Have someone carnk on the motor and see if the pump is getting voltage when it is supposed to.
If it is that might eliminate the fuel pump.

It almost sounds like there is something else wrong, but keep going in the direction you are if that is what you think is wrong.

Kinda hard to determine things over the internet......and I can't drive to NY to help out. (sorry).

Are you sure that everything is gettin power when you turn the key to run after start?

Did you change anything in the ignition from stock?

The reasont that I ask is that if you wired anything you may have just tapped the wrong wires. Just a thought. I still can't figure out how the fuel system wouldn't work in the run postition, just in start.


By the way the orange wire on the fuel injector harness is a ground. I just looked it up in the wiring diagrams. Make sure that you ground that one for sure.

I had a similar problem when I tried to fire up my car with the new motor. Check to see that you have the wiring correct on the solenoid, everything except the starter cable should be on the side that is always live.

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.

NP. Surprised that it was something to do with the pump. It's easy to miss things in the dark , and when you are tired.....