High and low fuel pressure errors
 

Boo-hoo , I'm still getting the 'engine service urgent....' message and limp mode on a very random basis. It clears with an ignition cycle.

The problem can occur at any time, trundling at 30, or caning it down country roads with no discernable pattern.
Also there is no code stored after an ignition cycle to help matters. I've been able to read it a couple of times whilst it's in limp mode, and both times it has been a fuel pressure issue, once high and once low.

I want to catch it again to be sure.

The car has had a new (known good) fuel pump, the filter was changed before I got the car about 5000 miles ago, but I may swap it anyway so I can rule this out.

I assume these cars must have a fuel pressure sensor, are these known to fail in this way? I can't think what else could cause random fuel pressure errors.
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When was the fuel filter last changed?
Really need the codes to be sure what the problem might be.
John

Filter was supposed to have been changed at last service (about 5k ago), but I have a new one that's going on tomorrow to rule it out.

Codes have stated both high and low pressure issued on Vida (can't remember exact code) and it isn't stored for some reason, the code clears with an ignition cycle, so I've got to read it without stopping hte engine when it occurs.

The fuel pressure sensor on the end of the common rail can fail and on the other end there is a pressure relief valve which can also fail . You can pick up a common rail complete with sensor and relief valve for £20. I did this myself on a D5 but unfortunately was not the culprit but mine was a different type of fault but at least its not a high cost item to try. Which pump did you replace in tank or injection ?

In-tank pump was changed, I've no reason to suspect anything other than an electrical or sensor issue, as I clear it with ignition off/on without even stopping. The thing is just so blooming intermittent it's hard to catch.

I've seen the sensor on the fuel rail, now. Will prob get another as a 'poke and hope' type change.

I have been considering seeing if I can get vida to log the rail pressure v's rpm whilst I'm driving to see what happens when the error occurs.

Finally managed to read the car in it's fault state, it shows 2 active fuel pressure faults. Anyone any ideas?

Changing the fuel filter tomorrow, just in case that's related. Edit: - just changed it, the old one looks like new, so don't think that's the cause unfortunately :( I'll be cutting the canister open to examine it in any case....

The car doesn't 'chug' as it did when I put the wrong tank pump in with a blocked return line which caused a genuine 'fuel pressure too high' code.

I'll be looking at the fuel pressure sensor next - I assume I need to depressurise the fuel rail, what's the best way of doing this?

http://img.photobucket.com/albums/v1...ps2c9b48f2.jpg

The car's now had a new fuel filter and is still dropping into 'limp mode', with a 'ECM 2505 - fuel pressure too low' code being flagged as active. Interestingly, this popped up whilst accelerating hard up a steep hill - and usually (but not always) pops up under load and with a warm engine. Does this give any clues before I spend more money on bits!

As soon as you mentioned "hill", I'm sure I've read a few posts about vacuum engine mounts or something like that.
No experience of it myself but hills have featured in the run up to similar sounding failings where the mount was the cause.
http://www.volvoforums.org.uk/showthread.php?t=101425
http://www.volvoforums.org.uk/showthread.php?t=196483

Thanks, but wouldn't the engine mounts give a boost pressure fault?

Not sure Reggit.
I'm sure I've read there's an easy test where you block off/clamp a vacuum hose to see if it makes the engine run better.
Worth a go maybe?