V70 petrol: Fuel starvation only when hot.Advice needed

[Luxobarge]

Hmm, that's interesting. You hadn't told us that the fuel pump relay had been changed....

I'd say that our previous advice still stands, but if that doesn't work then perhaps another fuel pump relay fault? Did you replace it with a high quality OEM (Bosch?) item, or a cheaper aftermarket one? These are not a simple relay, they're much more complicated than that, thus a decent quality replacement can be a bit expensive, but worth it to avoid further problems. Just a thought....

[CSCUK]

The fuel relay replacement was from a Volvo main agent.

The symptoms of the faulty fuel relay were entirely different to the present fault.
The engine wouldn't run at all until the relay was replaced.
Now it starts and keeps running perfectly until it gets warm, when it dies if you try to rev it, but continues running if you don't.

And if I gently increase the revs it will reach high revs and sustain them while I keep my foot on the gas. Then after long enough at high revs it "clears" (for lack of a better word) and runs and revs up completely normally without any sign of the dying fault.
And as far as I can tell, will continue to run normally while in regular use, with the dying fault only returning if I don't start it for a month or longer.

This pattern has been well proven by the two beach breakdowns and recoveries happening exactly like this. And after the second recovery I drove hundreds of miles making multiple stops (from minutes to a couple of days) without the fault returning until I reached home and left it for months without starting it. Then it did the exact same thing as at the beach.

This is why I thought it was a blocked fuel filter, because of it clearing and running normally simply by gradually getting it revving and keeping it revving for long enough, which completely cures the dying-when-revved fault and stops it reoccurring while it's regularly started and run.

Prior to this fault developing, it had been left without being starting for long periods throughout many previous summer's at beaches I was surfing, without this
dying-when-hot fault occurring as a result.

In case it does turn out to be the coolant temperature sensor. I've attached a pic of what I think is the correct part. Please confirm it is.

[richmac]

I thought you'd fixed it!

A couple of long shots to try that I don't think you've mentioned given that you're parked in very salty air for long periods. Have you cleaned your MAF sensor? 2 minute job with contact cleaner. When was the air filter last changed?

[CSCUK]

Can't fix it till after 28th Feb when I will get back home from working away.

Until then I can only collect advise and apply it later when I'm back, hopefully resulting in a fix.

It's been a while since air filter was changed, but it only does a low yearly mileage, being used only for surf missions.

I'll def clean the MAP sensor just in case.
Is it located in the air intake housing?

Cheers

[richmac]

Yes. I think this is even the same engine and mod year unless you are one of the last cable throttles:

https://www.bing.com/videos/rivervie...40BA&FORM=VIRE

[CSCUK]

Thanks Rich for link to good video.
However from the MAF sensor cleaning vid it looks like my model has a cable throttle.

I can't check for certain till I'm back home,
but I've attached a pic I had saved on my phone that shows the air cleaner housing and what I think is the cable of a cable throttle.

[Bob Meadows]

Yes a cable operated throttle here:~
That tape to the right also looks like a potential problem area.
Good Luck.
Bob.

[richmac]

Agreed! It may not be the problem but I suspect you need a new/ replacement intake hose looking at all that tape.

[DaveNP]

similar to Bob and richmac's point,
I can't really tell from the photo in post 3 but the foil 'hose' at the top of the photo that brings heated air from the exhaust manifold shield to the air filter also has a dark band which could be a split (or maybe a bracket?), it may seem inconsequential but if the engine is hot and the ecu is assuming hot air coming in throwing cold air down it's throat can cause it to stutter.

[Luxobarge]

Originally Posted by DaveNP

if the engine is hot and the ecu is assuming hot air coming in throwing cold air down it's throat can cause it to stutter.

Sorry, no, the ECU doesn't "assume" anything. The MAF has an air temperature sensor on it which tells the ECU pretty accurately what temperature the incoming air is. This hose being damaged won't cause the OP's symptoms, although I don't dispute that it's good practice to keep it in good condition.