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Discussion Starter #1
ok, so im trying to get my car running, (91 coupe, auto). when i turn the key on, the fuel pump isnt kicking on. i checked the fuses, theyre fine. i got a wiring diagram and busted out the multimeter, and im getting voltage to the relay on both hot wires. ok great. but when i turn the key on i dont get voltage out of the green/yellow wire. if i run a jumper wire across the relay, the pump kicks on, so its a bad relay, too easy... right? well i got a new relay, and it did the same thing, no change. maybe that relay is bad too? so i got ANOTHER one, no change. still, if i jump the relay the pump kicks on. if i have a jumper wire across it, the pump kicks on and stays on, and when i go to start it it seems like it starts but when i let off the key it dies instantly, although the pump is still on. so it almost acts as if the computer is shutting it off... which brings me to the next possible scenario. my low oil level sensor is bad, i know for a fact. (the wire came out of it) would this cause a no start? according to every wiring diagram ive looked at, it is no where near the fuel pump circuit, but will the computer not allow the engine to run if this is bad? please help!!!!

thanks, Jason
 

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Discussion Starter #3
[QUOTE='95.0 stang]Just to be sure, check the fuel pump cutoff switch in the trunk to make sure it didn't trip for any reason.[/QUOTE]
its fine, 110% positive
 
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Look at your wiring diagram, I'm to lazy to go get mine out of the car, and check all the voltages at the ignition switch.
 

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Discussion Starter #5
the ignition switch is new so i dont think it could be that.... also im only getting 11.3 volts to the fuel pump relay. how many volts does it need before it will kick the relay on?
 
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It shouldn't need more, the battery alone can't do much better than that. You said you checked hot wires, did you make sure everything was grounded too?
 

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A disconnected low oil level switch will not cause a no start. (Ask me why I'm so sure).
You can try taking the EEC diagnostic plug under the hood, and hold it so that the terminals are facing you. Now turn it so that the longer side is on the bottom. It should look like a house with the pent side facing up. Find the far right terminal (it would be downstairs). Connect that terminal to a good ground and turn the key to run. The fuel pump should run continuously.
You could also try testing the EEC relay too.
Have you changed out the starter solenoid, or had those wires off?
Also check your fusible links.
 

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Discussion Starter #8
meangreen92 said:
A disconnected low oil level switch will not cause a no start. (Ask me why I'm so sure).
You can try taking the EEC diagnostic plug under the hood, and hold it so that the terminals are facing you. Now turn it so that the longer side is on the bottom. It should look like a house with the pent side facing up. Find the far right terminal (it would be downstairs). Connect that terminal to a good ground and turn the key to run. The fuel pump should run continuously.
You could also try testing the EEC relay too.
Have you changed out the starter solenoid, or had those wires off?
Also check your fusible links.
now by doing that test, im testing the ground side of the control circuit of the fuel pump relay, correct?
 

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The Gree/Tan wire goes to the EEC and the EEC ground that wire to pick up the relay secondary curuit (coil) and turn on the pump (primary power circuit). Sounds like the solid state device in your computer that grounds the relay coil might be bad. You can fix this if you don't want to buy a new EEC just for that problem by running the Green/Tan wire through the primary circuit of a new relay and using an ignition "run" source to pick up the new relays secondary circuit. When the key is on the pump will be on and the inertia switch is still in the circuit for protection. Down side is the pump is on anytime the key is on. you could also wire a switch between the "run" power source and the secondary circuit of the new relay so that you could override the pump run in the key on position.
 

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jason91notch said:
ok, so im trying to get my car running, (91 coupe, auto). when i turn the key on, the fuel pump isnt kicking on. i checked the fuses, theyre fine. i got a wiring diagram and busted out the multimeter, and im getting voltage to the relay on both hot wires. ok great. but when i turn the key on i dont get voltage out of the green/yellow wire. if i run a jumper wire across the relay, the pump kicks on, so its a bad relay, too easy... right? well i got a new relay, and it did the same thing, no change. maybe that relay is bad too? so i got ANOTHER one, no change. still, if i jump the relay the pump kicks on. if i have a jumper wire across it, the pump kicks on and stays on, and when i go to start it it seems like it starts but when i let off the key it dies instantly, although the pump is still on. so it almost acts as if the computer is shutting it off... which brings me to the next possible scenario. my low oil level sensor is bad, i know for a fact. (the wire came out of it) would this cause a no start? according to every wiring diagram ive looked at, it is no where near the fuel pump circuit, but will the computer not allow the engine to run if this is bad? please help!!!!

thanks, Jason
You might have an EEC related problem. You are concentrating on the FP relay and I would check the EEC Power relay instead. Check it the same way you did the FP relay at the beginning. You might want to also check the EEC ground wire near the battery. If your car has both relays in the engine compartment relay box, I would check the small diode at the opposite end of the box from the FP relay location, IGN goes through this diode to the EEC relay. BTW, could you do a codes scan KOEO?lol
 

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fuel pump problem

check the ground signal coming from the ecm, if your not getting a signal for 3 seconds when you hit the key its probally the tfi on the bottom of the distributor, it controls the fuel pump operation through the ecm.(if no one believes me loosen your distributor,turn the key to the on position and crank the distributor left to right, the fuel pump will keep kicking off and on, just dont start the car during the test) the eec test harness has a wire in it that comes directly fom the ecm for the fuel pump you can test it fom there(remember that the ecm f/p signal is a GROUND signal.
 

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LXR4Ti said:
check the ground signal coming from the ecm, if your not getting a signal for 3 seconds when you hit the key its probally the tfi on the bottom of the distributor, it controls the fuel pump operation through the ecm.(if no one believes me loosen your distributor,turn the key to the on position and crank the distributor left to right, the fuel pump will keep kicking off and on, just dont start the car during the test) the eec test harness has a wire in it that comes directly fom the ecm for the fuel pump you can test it fom there(remember that the ecm f/p signal is a GROUND signal.
The 3 second priming is independent from the TFI. The reason why you activate the FP with the distributor is that the ECM is seeing the engine "cranking" by exercising the stator signal when you move the dist. left to right and activates the FP relay. This should be a good way to check the ground signal that goest to the FP relay like LXR4Ti mention.
 

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Joel5.0 said:
The 3 second priming is independent from the TFI. The reason why you activate the FP with the distributor is that the ECM is seeing the engine "cranking" by exercising the stator signal when you move the dist. left to right and activates the FP relay. This should be a good way to check the ground signal that goest to the FP relay like LXR4Ti mention.
This is correct..........
 
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