Faulty Fuel Pressure Regulator?
 

Hi all

Some of you may have seen my other threads about my engine troubles, but as I didn't choose very descriptive titles I thought I'd try again.

On my 940 estate, 2.3 normally aspirated, I get the following aggro:

* Lambda light comes on from time to time
* random lumpiness at idle (ok most of the time then the whole car will shiver briefly)
* Smell of petrol when first starting up, which I think is coming from the exhaust end
* Starts every time, but needs to be turned over a bit more than it used to.
* Random rough running and reduction in power

From what I've read, both in replies on other threads, and on the FAQs, it seems fairly likely to be the fuel pressure regulator that's at fault.

Could it be anything else?

Someone said that sometimes when they fail, petrol leaks down the vacuum hose straight into the inlet manifold after the throttle. Is this the only way they can fail or can they pull other tricks too? If so how would I diagnose it for certain without proper gear?

Are they a nice easy job to change?

If petrol has been leaking down the vacuum hose, that would cause the engine to run rich I believe. Would that mean the cat and lambda sensor will be done for?

Anyone?

Oh and I have an update: I pulled off the vacuum hose after driving home tonight. I did it straight away as soon as I'd switched the engine off. There was a faint wiff of petrol, but not much. I know that if there is a smell of petrol it is supposed to mean a bust FPR, but how strong a smell to indicate this? If it is a very weak smell, is it still bust, or does it have to practically take your breath away?

No ideas? I'm sure someone here knows?

Hi there,I have just spent half an hour searching my 940,740 and 240 manuals and it doesn't cover the fuel pressure valve except to say expect some fuel leakage when disconnecting it.
I would imagine that if the diaphram was leaking then the smell of petrol would be quite strong.The pressures involved in operating the valve are quite high so this would account for the running rich.
I'll keep looking,Regards Brian.

Fuel Pressure Regulator
 

If your FPR is original, and yours looks a bit rusty, you might wish to replace it anyway.
I got my OE Bosch one from PFV.
Alternatively to test yours, you could swap it with a known good one to see if it makes any difference.
Let us know what you find,
Ben

Thanks for the info chaps.

My FPR is little more than a lump of iron ore. It is the single most rusty part of the whole car, so I reckon I'll change it anyway. I'm just being tight by trying to avoid spending money too hastily in case it could be something else.

Another though occurred to me tonight. When I pulled off the vacuum hose, it came off very freely. I wonder if air is getting in though it, as that would be after the MAF sensor sensor, so maybe the lambda sensor was detecting a lean mix (am I right in thinking the light comes on if the mix is too lean as well as if it is too rich?)

I'm going to chuck through some fuel system cleaner in case the injectors are sticking. When I can afford it and have the time, I'll see if Jim on here will clean my injectors properly for me.

did you replace the rpm sensor.I remember one of your earlier posts saying that was one of the things you suspected.

I did at one point, after my car actually broke down on the motorway, but since then I found that the airbox was bust. Since doing a temporary botch on that, there's been no running trouble, just the occassional smell of petrol and once the lambda light came on. That's why I moved my attention to the fuel mix, and someone pointed me in the direction of the FPR. The trouble is, because I'm still learning all this mechanical stuff, I'm not that confident in my ability to diagnose and fix stuff. I was all set to change the lambda sensor when someone pointed out (and I'm sure they are correct), that the lambda sensor was probably just doing its job, and the problem was most likely earlier in the system.

On my '95 960 I had the fuel pressure regulator fail.

Symptoms were a difficult start cold or warm on petrol. More cranking than normal, difficult and lazy fire-up, petrol smelly exhaust, black exhaust smoke... As if partly flooded. Once started it always ran fine.

To find it I pulled the vacuum line off which is easily done with a slight pull as it is not on tight... and got someone to switch the ignition key on. It was dribbling petrol out of the regulator 'nipple' ... this petrol was otherwise being fed through the vacuum line into the manifold.

Got a used one for little money from Braydons who told me they hardly ever fail. Doddle to fit - at least on my 960.

Yours of course may be failed in a different way and so exhibiting different symptoms from mine.

Have you read the fault codes? If the Lambda is coming on then it should be logging fault codes that will at least point you in the right direction.