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Fuel pump still won't turn on


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zmaster: car is a 75 280z correct? Stock fuel injection correct? OK... to answer some of your questions the thermotime, tps and the ECU have nothing to do with the fuel pump getting juice. Like woldson mentioned at the begining of the thread, the AFM (air flow meter) has a cutout switch designed to cut juice to the fuel pump if the engine isn't running. It's a saftey feature so if the engine stalls in an accident fuel doesn't start a fire. Later model ZXs also had a cutoff switch wired into the oil pressure switch but you Z does not have this feature. Here is how to test it real easy. Pop the boot between the air filter and the AFM off. Turn the ignition to the on position with the engine not running. Stick your finger in there and tilt the flapper open a little bit, you should hear the fuel pump run. When the ignition switch is in the start position the fuel pump gets juice. If you wire the fuel pump directly without this saftey feature do so only temporarily to test the fuel pump. Just jumper it with a 12v source. You should be able to hear it run. Your ignition switch could be bad, check the fusable links as well. Read the EFI bible and trace the wiring harness down using the schematic Cozy Z Cole Larry posted. Keep at it man, you'll get it. And when you do, you'll be driving a cool thirty year old car nobody else has!!!

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i've been wanting to drive this car since may 11 of 2007.... its just been sitting and collecting dust for about 6 months then I really started working on it. i think you are right i think this problem could be the ignition switch....... I'll check this tomorrow. thanks for all of the help. I'll post tomorrow whether or not this was the problem or not.

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well i had to order the ignition switch from autozone because advance auto would have been in about 4 days, and autozone comes in in 2 days, so about friday or saturday my ignition switch will come in, but i can't put it on until monday morning, going out of town.

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ignition switch did not work at all!!! does anyone know which wire is the power wire to the fuel pump relay?? I have been thinking, maybe if i take a wire directly from the battery to the fuel pump relay, maybe that will get the fuel pump running properly again. what is everyones opinion on this??

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I've got a 260z, and at the moment I'm too lazy to figure out why the pump won't run by itself, but I have the same problem I think.

 

I just ran speaker wire from the battery up through the shifter with a switch, then back to the pump to run it whenever I want to. I'll get around to troubleshooting the stock wiring... eventually.

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That is exactly what i did to mine... Can you run your car with that switch on all the time, or do you have to turn that switch on and off??? I think if you run your car with that switch on all the time you will make your car run rich, or will the fuel pressure regulator send the extra fuel back to the fuel pump???

 

 

I'm starting to think it is the ecu, because i think it is supposed to send a little electricity to the fuel pump relay to turn the relay on which in turn turns the fuel pump on....and now I don't hrear the injectors pulse when the key is in the on position. Are they supposed to pulse to prime all of the cylnders???

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Well I can't speak for that. I'm running carbs on my L28, so the floats regulate my fuel for me. Dead-heading probably isn't too good on my pump, but w/e. I just leave mine on as long as the car is running, but yes a fuel pressure regulator would regulate the fuel flow, so no it shouldn't run rich.

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Ah well good then.

 

If that pic was shot with the car running, and assuming it's after the FPR then you have a problem somewhere. FI cars are supposed to have like 40+ psi of fuel pressure IIRC. Don't quote me on that, but I know that less than 10psi is definitely too low. You might have either a bad pump, the pump isn't getting enough voltage, or the FPR is bad. I'd check all of that if I were you.

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So you wired 12v through a switch to the pump and it turned on.

That eliminates any ground issues from the pump . Still doesn't eliminate the AFM or the ECU. Check for a ground signal coming from the ECU. Get the ECU pinout and look for the fuel pump signal. When the ECU is powered up just before starting the car, you should get a short to ground on that wire. That will ground the relay and send power to the pump. If not, you have a problem with the ECU. If you do have ground, then check the connection to the relay. That connection should also get ground when the ECU is powered up. If it doesn't, then you have a bad connection from the ECU to the pump relay.

Your gonna get tired of that pump switch after awhile.

Just think, if you get it running right, you'll have bragging rights.

My pressure is released when the engine is turned off after several minutes also. I think that is normal. :wink:

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