Depressurising fuel rail between runs.

[StrongSpearWorks]

Originally Posted by Laird Scooby

You have a vacuum gauge in yours? Could be useful for diagnostic purposes.

Have you cleaned and applied heatsink compound to the mating face of the ignition amp module at all? It's the sort of intermittent fault that they sometimes give before dying completely, cleaning the mating faces with non-abrasive solvent and polishing then applying new heatsink compound and refitting, giving it a jiggle to spread the compound around often gives it a new lease of life.

When I say Vacuum gauge I mean turbo pressure gauge… but I guess it amounts to something similar.
I’m tempted to replace the fuel rail with my spare purely because my spare has the pressure schrader (excuse my spelling) valve on it, where as my current one does not… by the by.

Ignition amp - known also as the power stage, bolted to the inside offside wing above the battery?

I’m my other life as an IT tech I have some thermal paste. I’ll try giving it a clean and some new compound. 🤞

[Laird Scooby]

Ah, yeah, the boost gauge - vacuum to the left of the "12 o'clock" position, boost to the right. I'm assuming it was at about the 8-9 o'clock position for normal driving when it started jumping around like a frog on a hotplate?

Which direction and how far did it jump mostly?

I'd leave the fuel rail alone for now, it might be the Schrader Valve is hidden somewhere you haven't looked as yet - a mirror is often helpful i use an old door mirror glass.

Power stage - Volvo-speak for ignition amplifier module is indeed on the inner nearside wing above where the battery is on turbo cars or washer reservoir and air filter on n/asp cars. Some PCB cleaner (IsoPropyl Acohol/IPA) works well to clean/polish the mating faces of the moduel and heatsink. Thermal paste is just a new word for heatsink compound and as i'm sure you know, don't use anything abrasive to clean those mating faces.

You may find it has little to no heatsink compound at the moment, i've experienced symptoms similar to yours on many cars including customers cars and fixed them by cleaning and applying a sensible amount of heatsink compound. For the most part, those cars had either no heatsink compound or literally just a spot in the middle.

[StrongSpearWorks]

Yeah, was plodding along in a contra flow and noticed a lack of power, needle started dancing back and forth between 8 - 12 (12 being no vacuum). Thankfully there was a gap in the cones and I drifted off to the side. Otherwise I would have made a lot of people unhappy 😬

I’ll pop it off this morning. I have some alcohol wipes that I usually use for cleaning heat sink compound off CPUs.

I imagine that after 30 years whatever compound was in there is nice and crispy now. I’ll give it a dab of Artic4 CPU thermal paste.

[StrongSpearWorks]

It was basically grey dust.
Surfaces cleaned. New paste applied.

The trial continues. 🙄

[Laird Scooby]

Fingers crossed that's the problem, if nothing else you've eliminated one possible cause. I forgot to mention this last night, while you're about it, follow the loom for the ignition amp back along the car to the suspension tower where you should find the earth point for the ignition amp, remove the bolt, clean the bolt, ring terminal and body and reassemble with some silicone grease inside and out.
Sorry i forgot that one last night but you should still be able to find that point fairly easily.

[StrongSpearWorks]

*Big sigh*


Same as it ever was, same as it ever was.


308 1.6 derv here I come 🫣

[StrongSpearWorks]

Having rechecked the ECT wiring and harness, confirmed at both ends my conclusion is that it can only be a leaking injector… fuel rail pulling time.
My thinking (could be wrong) is on cold mornings the ecu puts enough fuel in all cylinders to overcome the one that’s already full of fuel. When it’s warm, not as much is added, and hence the no-start scenario.

Plucking at straws here. Traffic jam theorising.

I replaced the fuel pressure regulator again with a new Bosch one - I used a spare of unknown performance last time, no effect on the starting issue.

Unless there’s a grounding issue somewhere holding an injector open which I’ve read can happen.

Edit. Might take it for a drive later, then disconnect the battery overnight. If there’s no voltage, then it couldn’t be a ground holding an injector open… worth a try at least.

Was going to look at a 2007 V50 tomorrow but have read so many horror stories about the Ford PSA engines that I don’t think I’ll bother 🤣

[Laird Scooby]

Originally Posted by StrongSpearWorks

Unless there’s a grounding issue somewhere holding an injector open which I’ve read can happen.

Edit. Might take it for a drive later, then disconnect the battery overnight. If there’s no voltage, then it couldn’t be a ground holding an injector open… worth a try at least.

Was going to look at a 2007 V50 tomorrow but have read so many horror stories about the Ford PSA engines that I don’t think I’ll bother 🤣

The grounding problem will only hold the injectors open if the igntion is still on as the RSR will disconnect power to the injectors when the ignition is switched off.

Also if the injectors were being held open like that overnight, they would probably burn out and you'd have a flat battery in the morning.

[StrongSpearWorks]

Originally Posted by Laird Scooby

The grounding problem will only hold the injectors open if the igntion is still on as the RSR will disconnect power to the injectors when the ignition is switched off.

Also if the injectors were being held open like that overnight, they would probably burn out and you'd have a flat battery in the morning.

Well there goes my theory 🤣 Wooooooosh….

[Laird Scooby]

Originally Posted by StrongSpearWorks

Well there goes my theory 🤣 Wooooooosh….

Just to clarify, that doesn't mean the theory of a mechically leaky injector should be ignored, just electrically that would normally give rough running.