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[Enceladus]

Might be the crank sensor. Or the fuel pump or the pump relay. Or any number of other issues including not enough oomph from your wife's car. The crank sensor is the first thing I'd like to be certain is working correctly.
 
Any particular reason why you wanted to change the spark plugs? I guess I'm really asking if the car was OK when you parked it up.

I think you're going to have to check for fault codes. Also the terminals in the OBD-II socket on the car can oxidise and impair contact. So wiggle the BT plug in and out a bit and see does that make it work.

[Doctor Gollum]

Some cars will flood if you look at them... Straight six BMWs for one... If you're to pull the plugs to check/dry them, you may as well change them

[Doctor Gollum]

In no particular order...

1. Is the car level?
2. Is there more than 1/3 tank in it. More important if answer to 1. is no.
3. If the answer to either of the above is no, address both by levelling and adding at least two gallons of fuel.
4. Now have someone crank the car whilst you give the tank a good slap from underneath.
5. If none of the above works, replace the crank sensor with a genuine one from a genuine Vauxhall dealer that you genuinely have to walk in to.

And report back.

[New POD]

It was working well before lockdown, but due a service, and so i had plugs ready.  They are 4 terminal ones, and the centre electrode was almost totally "worn away".

I had it running about 8 weeks ago because I was preparing my daughter's Bini, for sale and the battery was flat on that, so i moved the omega to start the Bini with jump leads.
Then I had the heart attack 6 weeks ago so, it's sat there.
4 in not understanding why the crank sensor would suddenly fail.

[Migv6 le Frog Fan]

When they fail, they often fail suddenly. 

[Nick W]

It was working well before lockdown, but due a service, and so i had plugs ready.  They are 4 terminal ones, and the centre electrode was almost totally "worn away".

I had it running about 8 weeks ago because I was preparing my daughter's Bini, for sale and the battery was flat on that, so i moved the omega to start the Bini with jump leads.
Then I had the heart attack 6 weeks ago so, it's sat there.
4 in not understanding why the crank sensor would suddenly fail.

Why wouldn't it fail suddenly? And how do you know when it failed over the last 5 months?


But you should diagnose properly before just changing stuff: recharge the battery, and get it drop tested; check that the fuel pump is pressurising the fuel rail(there's a test valve to do this) adequately after cranking the engine; how good is the fuel - a low level having stood for several months won't really be useful petrol any more; does the rev counter read when cranking over - not doing so points the finger at the crank sensor, but live data will confirm.


Battery is probably faulty. Weak fuel pump is a straightforward replacement with a NEW one. Same applies to the crank sensor, but that ought to be genuine GM.

[New POD]

Bear with me.  I need to take it slow, because need to pace myself. But brother in law came round with his cheapo scanner. Which always worked in it before.
It's showing no fault codes.
Petrol was filled up in March and I did 80 miles, so there's about 3/4 of a tank left.
Battery is properly dead.
With another battery connected it turns over and rev counter works.

[New POD]

Okay, there's definately fuel getting to the Engine.
With my best jump leads it's seeing 14.5 V from the car I connected it to, when cranking.
But no fault codes.
So it's going to be the crank sensor then?

[Doctor Gollum]

Yup

And categorically, only buy a genuine one from a genuine Vauxhall dealer that you genuinely have to walk in to 

[Andy B]

if there are no fault codes showing, why will it be the crank sensor? This car has been turned over slowly due to a flat battery. Is this not a flooded engine? ie like when cars have been started, moved a few feet & then left.

[Nick W]

if there are no fault codes showing, why will it be the crank sensor? This car has been turned over slowly due to a flat battery. Is this not a flooded engine? ie like when cars have been started, moved a few feet & then left.

crank sensor faults don't return codes. That's one of the symptoms. Live data should be used to confirm the fault.


If the OP hadn't already replaced the spark plugs, then a flooded engine would more of a possibility. But it should be considered, and so here's an effective way of clearing a flooded engine: fully charged battery; pull the fuel pump fuse or relay(whichever is easiest); crank the engine over for 20 seconds with the throttle fully open; pause, and repeat 2 or 3 times; refit the fuse and try to start - if it coughs or tries to start, you know you're on the right track. If that doesn't work, remove and dry the plugs using the gas stove or a small blow/soldering torch is most effective, and repeat the earlier procedure before you refit the plugs - this is the place to start if you suspect a flooded BMW I6, Jag V8 or Rx8. Engines like 1.0l Micras(not that there are many left) can often be started by replacing the fuel pump fuse as you crank it over - a trade tip

[Andy B]

....

crank sensor faults don't return codes.  ...

My 3.0 did ..... 19 IIRC

What's P0335 for then? http://www.omegaowners.com/forum/index.php?topic=90594.0

[Doctor Gollum]

That's the official code, but the Omega isn't entirely OBD2 compatible so doesn't throw up everything on the list

The lack of that very code is proof in itself that it's the crank sensor failing.

[Andy B]

That's the official code, but the Omega isn't entirely OBD2 compatible so doesn't throw up everything on the list

The lack of that very code is proof in itself that it's the crank sensor failing.

I believe you  .... just curious 

[mantamania]

I had this problem with my 2.6 about 6 years ago, would not start and no fault codes.  I replaced the crank sensor and it started first time and had no problems since. I personally did not buy one from the main dealer, the guy in my local independent parts place told me that Vauxhall do not make sensors for their cars.  They are made by Bosch, Semans, VDO and Delphi "formally Lucas".  As long as it is one of these brands he said it is as good as a GM part. The one i fitted was made by Delphi.