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[terry paget]

2.5 petrol manual estate
I have mentioned this before. Unlike my other Omegas, this car does not start well first start of the day. First 2 second starter squirt, nothing, second squirt it fires up. Restarts it fires up first time.

I thought it might be lost fuel pressure at the engine, so first thing this morning I removed the fuel pipes at the manifold. As I suspected, no fuel spurted out. Pressure loss at the pump end? A leaky injector?

I replaced the fuel pipes and started the engine. It immediately fired up. That puzzled me too.

[Nick W]

Unlikely to be a leaky injector.


Mine does this occasionally, especially when the fuel level is low and it's been standing for a couple of days. I suspect the pump is a bit weak, but don't intend to change it until the problem is consistent.

[Doctor Gollum]

Pressure regulator might be failing... it's on the fuel fail between the injectors and the return line. Cheap enough new

[cam.in.head]

Silly question but doesn't the fuel system prime itself for a couple of secs when you turn ign on ?.mine does or at least makes a sound like it does !

[MonzaGSE]

Silly question but doesn't the fuel system prime itself for a couple of secs when you turn ign on ?.mine does or at least makes a sound like it does !

No. On the v6 i believe the fuel pump wont run unless it gets a signal from the crank sensor. So the engine have to be turning before the pump starts. The four cylinder engines run the pump on ignition to prime however. Always figured that was why my girlfriends 2,0 fires immidiately when turning the key, while my 3,0 requires a couple seconds of cranking:)

[omega2018]

my v6 has always fired on first turn (touch wood)  however in the weeks before the crank sensor failed it would occasionally miss an instant start, still starting fine but just a very slight but noticeable delay.  could it be your crank sensor is on the way out?

[terry paget]

my v6 has always fired on first turn (touch wood)  however in the weeks before the crank sensor failed it would occasionally miss an instant start, still starting fine but just a very slight but noticeable delay.  could it be your crank sensor is on the way out?

I hadn't thought of that. Crank sensors are expensive, and troublesome on 2.5s. It would not explain why there was no fuel pressuire in the line yesterday morning, so I will change the pressure regulator first. Thanks for the thought.

[Marks DTM Calib]

Weeping injector is the usual suspect and have seen it a few times.

Usually, if you floor the throttle and spin the engine for a few turns its enough to re-pressurise the injector rail and flush the neat fuel out the engine.

Then second go it starts instantly

[terry paget]

Pressure regulator might be failing... it's on the fuel fail between the injectors and the return line. Cheap enough new

This fellow. I have a couple of 2.5 lower inlet manifolds in my spares heap. I could swop the whole thing, but that's quite a job. |Haynes says I should change the O rings, but amazingly these look pretty good. I am tempted just to change the valve.

 

[Nick W]

I would be measuring the fuel pressure before just swapping parts for the sake of it. Vauxhall even provided a test port to make it easy.

[terry paget]

I would be measuring the fuel pressure before just swapping parts for the sake of it. Vauxhall even provided a test port to make it easy.

It says 3.0 bar  on the valve, so I know the relief pressure. I presume you mean the pressure relief valve by a test port. I suppose if I press a tyre pressure gauge on the test port it should read 45psi or 3 bar. Is that what you had in mind? I have a PCL Mk3 tyre inflator which came with a calibration, though TB does not have too much faith is the calibration.
Or are you suggesting that I should test the fuel line pressure whie engine is running, then immediately after engine stopping, then the following morning? That sounds instructive. I could do similarly on a different Omega. It might confirm what having no fuel spurt out in the morning suggested.

[omega2018]

my v6 has always fired on first turn (touch wood)  however in the weeks before the crank sensor failed it would occasionally miss an instant start, still starting fine but just a very slight but noticeable delay.  could it be your crank sensor is on the way out?

I hadn't thought of that. Crank sensors are expensive, and troublesome on 2.5s. It would not explain why there was no fuel pressuire in the line yesterday morning, so I will change the pressure regulator first. Thanks for the thought.

you should always carry a spare crank sensor, a cheap get-me-home one will do.  Easy to fit especially if it has been done before (the cable will have been re-routed).  It might explain the zero pressure assuming MonzaGSE is correct.

[terry paget]

my v6 has always fired on first turn (touch wood)  however in the weeks before the crank sensor failed it would occasionally miss an instant start, still starting fine but just a very slight but noticeable delay.  could it be your crank sensor is on the way out?

I hadn't thought of that. Crank sensors are expensive, and troublesome on 2.5s. It would not explain why there was no fuel pressuire in the line yesterday morning, so I will change the pressure regulator first. Thanks for the thought.

you should always carry a spare crank sensor, a cheap get-me-home one will do.  Easy to fit especially if it has been done before (the cable will have been re-routed).  It might explain the zero pressure assuming MonzaGSE is correct.

Not so easy to change, as discussed before, though one slim OOFercan do it with the car on level ground.
I discovered this morning that access to the ptessure relief valve involves removing the plenum. Having done that changing the lower inlet manifold is easier. Hmmm.

[terry paget]

More data. Twice yesterday car started on second squirt, but promptly stopped again. Ir ran normally on third squirt. I still suspect fuel feed problems for above reasons, fuel pressure control valve, or fuel pump. Crank sensor was changed in March 2013, 30000 miles ago. Any thoughts, chaps?
This job is temporarily on hold while I change heater fan on V828.

[Nick W]

The pressure regulator is just a spring in a can.
The pump is an electric motor combined with a gizmo, and it has run all the time the engine has for the last ?? years.


With that in mind, which is more likely to present intermittent faults?