Omega starting problem

Looking for ideas ...

I have an Omega 2.5 V6 petrol with 82K on the clock that refused to start
over the weekend There was plenty of life in the battery but after an
uncharacteristically and unreasonably long period of cranking, the engine
refused to fire even once. Work circumstances forced me to leave it for the
mobile mechanic to look at today, and now it's working, but he hasn't 'fixed
it'. He reports that the car would not start for him either, but after an
hour of poking around and checking the ECU fault codes (no fault showing) he
tried again and it burst into life. He's concerned that he could find
nothing wrong whilst agreeing that there definitely WAS something wrong.
His only suggestion is that he changes "the main relay" (?) as a precaution
without any real evidence to suggest that it was the cause. For the sake of
twenty quid I told him to go ahead. He'll do it tomorrow (while I'm here)
'cos he has to collect it from a Vauxhall main dealer in the morning.

I've just arrived home from work and the car started normally enough,
although for the first minute or so, "chugged" a little bit as if it was
running rich, but it cleared and the idle setlled down smoothly. It doesn't
usually do that AFAICR but it may be that I normally drive off (gently)
instead of listening to the engine idling.

A bit of history :

- the car, which I have had from new, has almost never ever started on the
first turn of the key, but almost without fail (apart from now!) has started
on the second turn.
- the 'leaky rocker cover mod' was recently (couple of weeks ago) carried
out after discovering mucky leads and oil in the "plug 'oles". It was
noticed when doing a plug change to try to cure an occasional 'cough' when
accelerating hard. Rocker covers, gaskets, plugs and plug leads were all
changed and the car has run fine at all speeds and throttle openings since
then until now.

It's an estate car on an 'R' plate so it's worth about three and sixpence
ha'penny on the used car market, but it's still fast, smooth, comfortable,
spacious and reliable (until now, that is!) so I'm prepared to spend what I
need to (but no more!) get it back in top shape again.

Any ideas to help track down the cause and prevent me getting stuck again?

Please?

 

you mentioned nothing about the immobiliser?
if it has one, thats my prime suspect [relay].

next would be the crank sensor.

then poss coil pack. (suprised this did not fail after your earlier
problems)

my quick go

p'haps others can think of more.

mike

 

Fuel pump relay?

 

Thanks for your help. Sounds all good stuff ... I'll suggest the chap checks
these relays when he comes tomorrow. I presume the ECU would not report
these items as faulty? (Exclude the crankshaft sensor from that questions
'cos I know the answer to that one is 'no' - I had that problem a little
while back and the sensor was replaced by Vx main dealer There was no fault
code stored in the ECU to indicate a faulty sensor, but the Dealer suggested
that was most likely.)

It has no immobiliser but isn't there some kind of transponder transponder
built into the key (guessing here)? I tried both keys when trying to start
it anyway, just in case.

 

If there is aproblem with the transponder key not registering properly
then the engine management light flashes on and off as the starter is
cranked. Had that problem when somebody sold me an Omega with a 'spare'
key that had no chip in it!

My guess for your starting problem would be crank sensor, dunno why
these break so often :-(.

 

I'd second the crank sensor, or the wiring. My 2.5 V6 did exactly the
same thing, and the harness to the sensor was chafed and shorting to
earth.

Phil

 

If you replace the crank sensor run the new wires up to the ABS pump
and tie wrap there to stop it moving around. The original route is
along the oil pipes to the oil cooler and the heat causes the cable to
fail.

 

Thanks for all these responses. The crank sensor was replaced by a Vx
Dealer earlier in the year and of course I had no control over cable
routing. The "main relay" (the one described by Mr Haynes as the Fuel
Injection relay) has now been replaced, and on each occasion of starting
since then (only about 6 or 8 times so it's early days yet) it has started
on the FIRST turn of the key, something which since new it has almost never
done, so I'm cautiously optimistic that there may be an improvement.

Rodney, the name is spookily familiar - I don't know if I've seen it before
in a cars forum, or did you used to work for the computer company Digital
Equipment Co. in a previous life, from a place like Warrington or some other
exotic location north of Watford?

 

Not DEC. I did work from Sheffield and covered that area but way back
in the late 70's/early 80's. Then worked out of Leicester and then at
Luton. I worked for Systems Reliability, a third party maintenance
company. I've been posting occasionally in the car groups for a few
years and a couple of Vauxhall/Omega forums recently.

 

(snip ..)

Prob'ly from another forum then ....