No power to fuel pump

[dkloder]

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]

You have a V6 ?? The power to the fuel pump goes through a oil pressure sensor when key switch is on. This sensor is bypassed when the key is in the start position.
Do you have a wiring diagram ?? Have a look at this -->http://www.memcals.com/pdf/VRV6%20Ma...%20Diagram.pdf

[wamboin23]

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]

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]

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]

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]

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]

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.

[delcowizzid]

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]

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.

[dkloder]

Have checked the series of the motors. We have put a series I in and pulled out a Series II. What now??

[Cheap6]

Maybe check again the connectors near the PCM. I think that there are three(?). I've been caught before forgetting one of them and one does connect to the fuel pump relay.

If you jumper power and earth to the fuel pump (get the pump working under its own power again) does the car start?

If you jumper the switched side of the fuel pump relay does the pump run (that will tell you if the problem is on the PCM - switching - side or the fuel pump - switched - circuit for the relay)?

Do you have a CEL with the ignition "on", engine off i.e. is the anti-theft allowing the PCM to work? (You can have spark from the DFI without the PCM working).

Have you checked that the fuel pump hoses are the correct way around on the fuel rail i.e. feed not swapped with return (I know you have said that the pump is not getting power but it can't hurt to check everything ).

Series I and Series II VR work the same way, both are batch fire, firing the injectors in groups of three but that said, there may be minor differences in the engine wiring harness.

[dkloder]

Sorry for my ignorance, but what is the PCM and CEL?? Between the relay box and the connector at the fuel pump, are there any other plugs or connections in the harness that could have been pulled out by accident, cutting the power to the pump?? Thanks for your help Cheap6. Actually, thanks to everyone for your input so far..

[FstStig]

PCM is your Powertrain Control Module It examies the fuel, coolant temp, camshaft(if camshaft sensor is there) crankshaft(CAS), Ignition, valve timing, and Air intake. If one of these fails then it will turn on the Check engine light. I suggest you check your MAP sensor (Manifold Absolute Pressure Sensor) It measures the amount of fuel pressure going into your injectors, if this is stuffed then it will stop the car from firing, will allow it to crank but not fire.

[Cheap6]

PCM: Powertrain Control Module - computer
CEL: Check Engine Light - the little orange engine silhouette with the exclamation mark inside it in the row of lights under the instruments.

There is a connector that runs a wire to the fuel pump on the driver's side , behind the kick panel, purple wire but you shouldn't have touched that (did you?).

What happens to the fuel pump when you bridge with a wire the terminals that connect to the fuel pump relay pins 87 and 30, ignition "on" (see the side and underneath of the relay for the pin #'s)? Does the pump run? (Relay oriented as installed to match the pin locations.)

[dkloder]

Well, we found the problem. One of the guys had disconnected a wiring connector above the computer. I can only assume he thought it was connected to the computer itself. Anyway, we plugged it back in and away she went, and out coolant poured from between the radiator and the aircon radiator. Not too sure why, that was never touched. Anyway, main problem solved, and we go tthe fuel pump changed anyway which was bound to fail eventually. Think we have the linkage on backwards on the gearbox, but sending it to the mechanic to tidy up a few lose ends.

[delcowizzid]

told you dash to engine loom everyone forgets to plug that in LOL

[dkloder]

yeah, cheers Delco. I was thinking more under the dash near the steering wheel rather than over by the computer. Didnt think anyone got under that part so didnt look LOL

I'll hijack my own thread here. We have a problem with the gear linkage. Not sure which way it goes in. Does the locking bolt face the gearbox or to the outside??

[weston]

told you dash to engine loom everyone forgets to plug that in LOL

Hi delcowizzid im doing a VH with a series one VNV6 in her with the trans andusing the whole vn loom in the car, i to have the problem with my pump not seem to be working and womder if the s1 vns have this plug you were saying of dkloaders vr.
How many wires are involved on this plug so i can look at mine and see if its plugged in i think it is but never know. Best to my knowledge i can hear the fuel pump relay and have even swapped one of the others to check and seems right but the pump has no sound and i checked the four wires at the tank with my test light but nothing?
I also pulled off the supply hose from the tank and put on a short bit into a bottle and cranked the motor but it didnt even pump one bit of fuel, is it power related or is the pump shagged, i would realy like to get the car started soon cheers