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No power to fuel pump

dkloder

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Hey guys,

I have just replaced the engine in my VR Commodore. I took the engine and gearbox out of another car and dropped in mine. Everything connected up perfect, but will not start. Engine turns over, but no fire. This car has a fuel pump history, but even then, you could at least hear it running when it was working. Since putting the motor in, it has stopped. I removed the power plug on the tank and ran a test light, no power. I called the NRMA and they found a lose wire under a relay, but still no go. After testing everything, he concluded the fuel pump was no good (he even said he could hear it buzzing, I couldnt) and that it was not producing enough pressure. Im not convinced. There is no 12v at the fuel pump. I connected an old battery directly to it, and although it did not run under full power (the battery was a bit dead), it still ran. So given that all the relays, fuses have been tested and are working fine, What else could the problem be?? Im not going to replace the fuel pump if there is no power there. What else could cause a loss of power to the pump?? Could we have pinched a wire that runs to it.

Cheers all, great site.

D
 

woteva

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wamboin23

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the power does not run through the oil pressure switch.

it only runs through it if the fuel pump relay is not turned on for whatever reason.

to the OP, is the fuel pump relay turning on?
 

hako

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It's possible the OP is confused or whatever.....when you turn the ignition ON, the pump will only be powered for a second or two....not continuously. It will only get power continuously when the engine starts and oil pressure is up. So if you turn the ignition on, then check the power at the pump, there will be NO power.
 

dkloder

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The guy from the NRMA checked the relay and it was working. My main concern is that we have not connected a wiring plug somewhere. When I disconnected the plug next to the tank, I was not getting any power on reds, and even while the engine cranked. The fuel level cable did have power. The NRMA mechanic checked all the usual things, but for some reason he thought the pump was running and said it was the pump that had failed. Pump is working when attached to its own power.
 

hako

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The guy from the NRMA checked the relay and it was working. My main concern is that we have not connected a wiring plug somewhere. When I disconnected the plug next to the tank, I was not getting any power on reds, and even while the engine cranked. The fuel level cable did have power. The NRMA mechanic checked all the usual things, but for some reason he thought the pump was running and said it was the pump that had failed. Pump is working when attached to its own power.
You should NOT get power with the key on reds.....except for a brief 1 or 2 second blast to prime the system. However, as you know the pump runs under it's own power, try powering the pump and then crank and see if it starts.
When you replaced the engine, did you use the same series VR engine?...I seem to remember that the series 2 had sequential injection and also a cam position sensor so maybe the problem lies there???
Another thing is that all Commodores need a fully charged battery to start......anything suspect will fail. Good Luck. ps...try swapping the FP relay with another from the relay bank.....also there is a fuse somewhere in the circuit...number 12???
 

dkloder

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It's possible the OP is confused or whatever.....when you turn the ignition ON, the pump will only be powered for a second or two....not continuously. It will only get power continuously when the engine starts and oil pressure is up. So if you turn the ignition on, then check the power at the pump, there will be NO power.
Before the change, you used to be able to hear the pump for a second or so, nothing now. This is how I knew there was a power issue. Im not sure what the NRMA guy thought he was hearing, but it was not the pump.
 

dkloder

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I'll have to check the other car to see if its the same series. Battery is fully charged and the car turns over quickly. NRMA mechanic cleared any fuse or relay issues. Looks like Im pulling out the pump from the other car, even though I know its not likely to solve the issue.
 

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did you swap in a whole new harness with the engine and trans if so did you plug in the dash to engine loom plug under the dash if you didnt plug that in or if you have a harness from a different model some pins are swapped in the plugs and are in the wrong places.do you have spark or at least power to the dfi and to the injectors
 

dkloder

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Injectors, spark plugs, its all working. Just missing the fuel pressure. As for the wiring, the only looms that changed, afaik, were the ones that went from the motor to the computer. I dont remember any looms being disconnected to the inside of the car other than the loom that went behind the glove box to the computer. We have pulled the computer out of the other car, thats an easy thing to change, should we start there and see what happens?? I'll confirm the series today to get that issue out of the equation.
 
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