I'm trying to get my motor started for the first time. It'll start but shut down right away. I'm getting spark and fuel pressure. 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
Fuel pump help needed NOW!!!
- Thread starter Andy00018
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Stang951
Founding Member
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.
Stang951
Founding Member
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.
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.
Yea, I hear everything clicking on only in the start position, but once i release it nothing. The fuel pump is suppossed to turn on in the accessory position right? Its like it starts then once I release the key so the car can idle it just shuts down? I'm almost positive it has something to do with the fuel pump.
I have a 91. Yea I replaced the ground strap, there was only 1, I put it from a behousing to engine bolt then wired to the firewall. I double checked all the connectors and the harness has 1 wire not hooked up. Its an orange wire coming from where the fuel injector wires are coming from. It wasnt hooked up before I took the motor out, and i think its the injector ground wire, i heald it down to ground it but nothing different happened. I took out the relay under the seat and put it back but I dont know if that would have anything to do with it, do you think it could have went bad? But its wierd that the pump is turning on not in the accessory but the start position. Also I didnt touch the computer.
Stang951
Founding Member
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).
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).
Yea, I'm positive its not running in the run position. This isnt a problem I expected to have after putting in my motor. Again its getting spark, It is getting fuel but when I put it back in the run the car dies instantly. I hold it for a second longer and it stays on, but i dont want to hold it for too long because I dont want to grind out the starter. I could be wrong about the pump but its almost like its the only thing it could be, plus the odd fact that it only turns on in the start position. Do you think it could be the relay by an chance, or is that sorta eliminated because it does turn on. Thanks by the way for helping me out.
Stang951
Founding Member
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.
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.
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.
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.
Thank you everybody!!! And especially Stang951, I got it running, it ended up being one stupid little connector under the hood that I didnt hook up, It was hidden next to the battery and the other side of it was tucked under the solenoid and I thought it was running to it, hard to tell at 9 last night. when i hooked it up I got the pump to come on in the run position then it started right up. Good thing it was something dumb and free!!!
Stang951
Founding Member
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.....
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