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[omegod]

Got a spare pump and crank sensor knocking about cheap if needed

[terry paget]

Thanks chaps. Today I fitted two good violet relays, GM90 494 959, cranked engine, did not start. Had wife crank engine while I thumped centre of tank with plastic mallet (found it hard to kick there) but, in vain. did not start. All worth trying, thanks for tips.  I am out tomorrow, using OE03EWW, 3.2 with slipping clutch, but will renew investigation Saturday. I shall test volts on wires to pump on cranking and report back. Any new suggestions, please keep them coming.

[05omegav6]

Crank sensor it is then

[terry paget]

Crank sensor it is then

I hope you are right. Al. I have changed five in the past, it is a simple job, However, my memory is that when a V6 Omega refuses to start, but cranks vigorously, the first thing I check is fuel feed by loosening the feed hose and cranking. If fuel spurts out, the fault lies elsewhere, almost certainly crank position sensor. In this case, fuel did not spurt out. So I suspect fuel feed failure.

Senators were devils to start in the winter if they had more than five days without use. The distributor right at the front behind the cheese grater grill got damp, then it would either not start at all, or start on two or three, and take quite a long run to dry everything out. Omegas are much better, with coil packs at the rear of the engine and no distributors.

I will keep in touch. I shall check there are 12 volts to the pump when cranking, if there are  not I shall bring 12 volts to it. If there are 12 volts to it and it pumps, then it must be crank sensor.

I have not checked for spark at plug. I suppose I could take a lead off, put a spare plug in it, lay it on the head and crank engine. No spark would confirm crank sensor fault. Spark would suggest dead pump.

Any thoughts?

[05omegav6]

You're unlikely to find voltage at the pump without the engine running, based on Marks' suggestion that it doesn't prime when the ignition is switched on

[terry paget]

You're unlikely to find voltage at the pump without the engine running, based on Marks' suggestion that it doesn't prime when the ignition is switched on

With just the ignition on, no. But with the starter cranking, yes . Otherwise the poor thing has no chance of starting. I believe the fuel pump relay is activated by the starter relay circuitry. Once the engine starts the crank signal sensor holds it in.

[05omegav6]

The engine will run for about 5 seconds with the contents of the fuel rail

[Marks DTM Calib]

You're unlikely to find voltage at the pump without the engine running, based on Marks' suggestion that it doesn't prime when the ignition is switched on

With just the ignition on, no. But with the starter cranking, yes . Otherwise the poor thing has no chance of starting. I believe the fuel pump relay is activated by the starter relay circuitry. Once the engine starts the crank signal sensor holds it in.

Its not, its activated along with the spark and injectors once a valid crank pulse is seen (hence why we see miss diag sometimes as when the crank sensor fails people rush off checking the fuel pump relay and fuel pump as there is no fuel to rail).

Fuel pump is under ECU control

[terry paget]

You're unlikely to find voltage at the pump without the engine running, based on Marks' suggestion that it doesn't prime when the ignition is switched on

With just the ignition on, no. But with the starter cranking, yes . Otherwise the poor thing has no chance of starting. I believe the fuel pump relay is activated by the starter relay circuitry. Once the engine starts the crank signal sensor holds it in.

Its not, its activated along with the spark and injectors once a valid crank pulse is seen (hence why we see miss diag sometimes as when the crank sensor fails people rush off checking the fuel pump relay and fuel pump as there is no fuel to rail).

Fuel pump is under ECU control

Thanks Fuse 18. Just to get this straight, fuel pump relay is actuated by the ECU when it gets valid crank sensor pulses and by nothing else. Thus, with ignition on, engine still, no pulses, no volts to pump. But with starter cranking engine we get crank sensor pulses, which trigger volts to pump.

So if I check spark at plug lead when cranking and find one, crank sensor is OK, fault must lie in pump (or leads to it). If I get no spark, crank sensor is dead.

Please confirm.

[philhoward]

Sounds a logical assumption to me.

[Marks DTM Calib]

From memory, K43 is the injection system relay that supplies the pos volts for the injectors (plus some of the vac actuators) and is ECU controlled, this switched pos feed from K43 then turns the fuel pump relay on (K44).

[terry paget]

You were all right and I was wrong. Found no spark this morning. So it's crank sensor. It's a 2.5 so model is it's critical that I replace with original fitment, which is labelled GM 90462061. Have you got one, Omegod?

Thanks for your help chaps, saved me wasting my time playing with the fuel pump.