Fuel upgrades, car won't run. Need help ASAP! :(

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.

mansonozz said:

Set my TPS to .97 this morning. Still no luck.

My mechanic friend came over and we tried pulling codes, but the comptuer is not readable. Any ideas now?

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What do you mean not readable? Maybe it's bad? Got another or a friend with one that you could try??

I've only got a DA1 computer which is speed density. I just sold my maf computer to a friend which is in his car right now, sorry...

Are you using a scanner, or the old paperclip and test light trick? You probably can't keep it running long enough, huh?

just trying to help out

Hey , I'm in West Springfield. I have a mass air computer you can try if you want.

Sounds good! Try out Tinos computer hopefully thats the problem.

Check the voltage of the Signal Retun wire & the v-ref wire down at the EEC, if voltage is good there (KOEO), then run a jumper wire from the Signal Return to a good chassis ground. Try to pull the codes ... if the codes will pull with the Signal return wire grounded chances are the EEC is shot....

BUT

Are you getting power back to the FP or no? Have you checked the wiring for the pump/relay/inertia switch?

Good Luck!!
Mike

=Printed those out, labeled 88-91. Mine is a 92 and most wires are colored different. But from those we got the idea that the EEC power relay was shot, since it wasn't powering back to the computer.

Thanks on the other explanations, I'm going to be busy tonight!

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Pull off any of the fuel injector connectors and look for +12 volts on the red wire. No +12 volts, ECC relay is suspect. If +12 volts is good, then the computer is suspect.

Look for VREF (+5 Volts) at the TPS ,MAP or EGR sensors.

Check the ground at pins 40 & 60 on the computer with it powered up. You will need to probe the pins from the back of the connector, a safety pin or paper clip is helpful. There should be less than .5 volt between the computer ground pins and battery negative post.

Look for +12 volts on pin 1 of the computer: no +12 and the ECC relay is inop. You'll need your safety pin or paper clip again to gain access to the back of the pin.

So what's the verdict OZ man ?

I hope it's not something that will kill an eec, such as if you put in another and it fries it.

Well if you've checked the wiring well where your having issues, checked your power & grounds good & it's not any of the specific components it only leaves the EEC I just had to replace mine after what 7 years? Put the new one in & I have no issues what so ever now. FWIW ...good luck man!

Mike

Its a long shot, but hit the inertia switch so it pops and reset it. See what happens, worked for me once..