Fuel pump wont prime or pump... HELP!

You did check fuses as well right. Make sure that the fuel pump is getting power with a test light or volt meter, and assuming you did rehook the harness on the tank, as well as properly run the lines from the fuel pump housing to the pump itself, you probally got a bad pump.

Drop tank, check for power to the housing, if it still has power, pull the pump and check power to the pump itself, if it has power, then it is the pump. I know, I know, it's a PITA, I went through it last week.

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 wire) then from the inertia switch to the relay coil and then from the relay coil to the computer (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 brown 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




Be sure to check out the links to the diagrams -they are worth their weight in gold when you are trying to understand and troubleshoot a problem.

jrichker im trying to find that fuse link you said is around the starter relay i have a 1995 mustang gt and my starter relay is in the fuse panel under the hood i have a regular fuse for the fuel pump in the fuse box but im not seeing the fuse link in the wiring harness would it be rite around the fuse box ?

Bottlerocket - it is VERY important that you check to see if power is going to the tank side of the connector. I had a similar problem where my pump would work when it wanted to. It ended up being the connector right at the back of the fuel tank, where the pump pigtails plug into the harness. Take a test light and make sure you are getting power through those connections. Good luck.

nate12281 said:

jrichker im trying to find that fuse link you said is around the starter relay i have a 1995 mustang gt and my starter relay is in the fuse panel under the hood i have a regular fuse for the fuel pump in the fuse box but im not seeing the fuse link in the wiring harness would it be rite around the fuse box ?

Click to expand...

The fusible link pertains to fox III's. As you noted, in 94 they cleaned things up under the hood and installed a secondary fusebox with a fuse for the FP.

If you need to test the FP pathways, the FP relay is housed in the CCRM.

Good luck.

tunedin302 said:

Bottlerocket - it is VERY important that you check to see if power is going to the tank side of the connector. I had a similar problem where my pump would work when it wanted to. It ended up being the connector right at the back of the fuel tank, where the pump pigtails plug into the harness. Take a test light and make sure you are getting power through those connections. Good luck.

Click to expand...

Same here... When I dropped the tank for drilling my battery box the harness got a bit stretched and caused the wire to pull itself a bit out of the connector. Pushed it back in and it was good to go