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[John_Clayton]

Can anyone tell me exactly where the Fuel Pump Relay is? The Haynes manual says it's no. K44. It has a photo (p.4A.15) but it's different to mine so doesn't help. The Vauxhall handbook doesn't help either. I have 2 purple relays at the back of the relay box by the battery. Then there's 3 orange ones, then a grey one, 2 green ones, a black one, a white one and another orange one right at the front. I can't see the wire colours without taking them all out. I don't have any power on the fuel pump or the fuse so want to check the relay.

[TheBoy]

Check Tech info section, Marks_DTM posted up details of relay box for each engine type

[Kevin Wood]

Of the two purple relays at the back of the box, it's the one nearest the  passenger side wing, IIRC.

Kevin

[John_Clayton]

Thanks for those replies. The layout on my Omega doesn't match the one Mark shows in the Technical section and the Haynes manual talks about early and late cars so presumably they changed the layout at some point.

[John_Clayton]

Of the two purple relays at the back of the box, it's the one nearest the  passenger side wing, IIRC.

It turned out to be the one furthest from the wing (i.e. nearest the engine). According to the plan on the cover it's relay no.40. Anyway, the relay isn't switching when I turn the ignition on. I'm getting supply to it but I can measure 12 volts on both coil pins so it's not being earthed, i.e. no voltage drop across the coil. The Haynes wiring diagram shows that wire going into the Control Module which I assume is the ECM. I've done the paperclip test but only get codes 12 and 31. Any ideas?

[Grumpy]

You haven't said what your problem is that is causing you to check
your fuel pump is running.
Is this a failure to start?

I'll make a possible incorrect assumption that your V6 is set up
similar to my 4 pot.
What happens here, is that when you initially turn on your ignition,
the ECU signals the fuel pump to run for a few seconds to prime
your fuel system. It then switches the pump off and isolates the
relay (probably via the Earth return, haven't rechecked the wiring
diagram).

It will not then re-energise the relay and switch the pump back on
until it gets a valid Crank Sensor signal.

Does this information help you at all with regard as to when you are
checking your relay and the results you are getting.?

[John_Clayton]

You haven't said what your problem is that is causing you to check
your fuel pump is running.
Is this a failure to start?

Correct. I've completely rebuilt the engine and it won't start. There's no pressure in the fuel system as I've loosened the nuts on the fuel pipes at the engine and nothing comes out. There's no power on the pump or the fuse (as I mentioned in my first post) hence the focus on the relay. Do I get another ECM (expensive!) or have I overlooked something?

[Grumpy]

Making the assumption that your ECU, Fuel Pump and Relay were
working prior to removing and rebuilding your engine, I would
consider that it is more likely that you have a defect in the items
you have removed and worked on than the items left in place and
not touched.

I would arm myself with the wiring diagram and a multimeter and
set about checking all disturbed circuits within the engine bay.
First for continuity, to ensure the circuit is complete and undamaged,
and then for correct operation when powered in the correct sequence.
Pay particular attention for damaged connectors or trapped/chafed
wires.

The expensive ECU would be last on my list for replacement to be
quite honest.

[Marks DTM Calib]

It could still be total failure of the crank sensor...........a code 31 is for no signal.....and if the wire or sensor is totally knackered then you will get a 31 and the above symptoms.


It doesn;t sudgest ECU at fault as its booting up and talking to you as proven by the paper clip test.

[Kevin Wood]

I have found my V6 doesn't even prime the fuel system with the ignition switch. It doesn't energise the fuel pump until the engine is first cranked so it has a different strategy to the 4 pots.

You could check the fuel pump is priming by removing the relay and bridging the contacts (the two wider pins). It should run continuously then.

Does sound like a crank sensor failure though. Given that the wiring on these fails gradually in the hot environment, if it has been pulled about a little during the engine rebuild this may have hastened the failure.

Is there any sign of life? Fuel injectors firing? Coil pack firing? If not, it points to the crank sensor.

Kevin

[John_Clayton]

.....................
Is there any sign of life? Fuel injectors firing? Coil pack firing? If not, it points to the crank sensor.

I found a bad connection at the large circular connector behind the battery and the fuel pump now runs when the relay is shorted. However, with the relay in place I only get about one volt at the terminal when the engine is cranked.  

I've checked a plug lead. There's no spark on no.1 plug lead. I don't know how to test the injectors. I've also checked the crank sensor. I get a resistance of about 800 ohms between 2 of the terminals, and it changes when the engine is cranked so I assume it's working OK.

I could check every single circuit but it would takes forever so I'm going to call in a mobile diagnostic specialist. Thanks for all the help to date.  

[Kevin Wood]

If you've had one dodgy connection there you could have more, so make sure that connector is properly home.

What happens to the dash lights when you turn on the ignition and subsequently crank it? Have you got a flashing EML (immobiliser issue?).

If not, my suspicion is still crank sensor. Most other circuits from the ECU to the engine would result in some activity. I.E. Injectors - 6 separate circuits. Engine would fire unless all 6 are shot. 3 Separate coil pack signals, etc.

Kevin

[John_Clayton]

The saga continues. A mobile repair guy came round yesterday and diagnosed a crankshaft sensor fault, as suggested by Kevin. However, I bought and fitted a new sensor and it's made no difference. I've therefore started tracing the wiring back to the ECU. According to the Haynes manual the sensor goes to pins 48 and 49 on the ECU. Well, not on my engine it doesn't! One goes to pin 12 and I don't know where the other goes. Another guy (recommended by the first chap) is meant to be turning up tonight but hasn't arrived yet. The only good news is that I don't have a deadline to get the car going - at least not for a few weeks! Any comments?