D5 (D5244T to 2005) High and low fuel pressure errors

[Bernard333]

Originally Posted by reggit

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?

There could be residual pressure in the rail and you dont want a jet penetrating your skin or eyes but I just put a rag over one of union nuts and slacken it off, normally just a dribble will come out, I wouldnt do it with the engine running. You can see the rail pressure drop very quickly ( within a few seconds ) in Vida when you switch off the engine. So far have not needed to use new pipes on injectors/pump and no leaks.

[reggit]

Hmm, been doing some logging on vida before spending any more. However I managed to get the fault condition active and the engine stalled (I was on my own so delibarately trying to get it to fault), I'm now suspecting this is an actual lack of fuel to the engine, however it's got a new filter and a working tank pump - where to look next?

Looking at the graph (last 1/5 screen), it looks as though the fuel rail pressure dropped just before the 'engine service....' and limp mode came on. What does this tell me, I'm no blooming idea!

[reggit]

10 minute leakback test - duff injector?

[Yosser]

Originally Posted by reggit

10 minute leakback test - duff injector?

Looks pretty even to me, not too much volume for 10 mins either I reckon.

[reggit]

Found out the injectors are well within spec, I was worried about the second one in that pic as it was flowing twice as much as the others - changed high pressure pump a few days ago, seemed not to make any difference at first (air in fuel?) but now it has settled down and hasn't thrown the fault for a couple of hundred miles including me trying to provoke it.

It now takes a little longer to start, but I can live with that for lack of 'limp mode' at the slightest provocation up hill.

I'm not saying it's better yet though as it will need longer than a few days for me to be happy with it again.

[reggit]

Well it's been a few months and the blooming fault is still present.

Since I last posted I've found out it only seems to fault with a high fuel level - I've been temding to run the car with half a tank or less, however I brimmed it at weekend and the limp mode fault has reappeared. I've also substituted the fuel rail pressure sensor with a known good one and that makes no difference.

I am starting to run out of ideas, other than use no more than half a tank of fuel.

I've just logged a bit of data and it is still showing that the rail pressure and current through the rail sensor both hit minimums as the car faults. I'm thinking of re-wiring the rail sensor as there is no slack in the cabling - but after that I'm stuck!

Relevent active codes are
ECM 2501 - fuel pressure too high
ECM 2505 - fuel pressure too low

Both of these are shown active in vida at the same time, so i assume must be read from different sensors that are disagreeing with each other?

[Lancee]

Straw clutching now. Volvo OE fuel filter or other fitted?

I had a very nasty intermittent fault on an accelerator (V70 D5 185) caused by fluctuating supply voltage due to a dirty fuse blade.

Try cleaning any fuses in the relevant circuit.

Keep at it and don't give way to despair!

[Bernard333]

Originally Posted by reggit

ECM 2501 - fuel pressure too high
ECM 2505 - fuel pressure too low

Both of these are shown active in vida at the same time, so i assume must be read from different sensors that are disagreeing with each other?

I think the only pressure sensor is the one on the end of the fuel rail . Over a period of about six years I have had failed in tank pumps , measured the current flowing in good ones, substituted D5 pumps for petrol pumps , none of it made a difference to whats happening on the high pressure side of the injection pump as long as there is some fuel being delivered to the injection pump. Something I noticed was that any slight acceleration or incline on the motorway and the in tank pump would be switched on and its definitely not audible when cruising even with the rear seats and soundproofing removed , the easiest way to see this happening is to wire an ammeter into the in tank pump supply circuit. A Picoscope or similar can show up faulty segments on the in tank pump commutator but this just means a small reduction in pump output rate which is not critical for a Euro 3 D5 engine. I am assuming you have checked the fuse on the end of the dashboard ?

[reggit]

Thanks for your input Bernard,

I know the pump is working, as I habitually run the level to the red, if it was dead it would cut out at 1/8th tank.
Also it doesn't explain why the car only faults when the tank is over around half full, when it is low on fuel it runs faultlessly.

The fault however manifests itself on gentle inclines which would suggest a pump issue.

I'd starting to get confuddled!

[reggit]

Originally Posted by Lancee

Straw clutching now. Volvo OE fuel filter or other fitted?

I had a very nasty intermittent fault on an accelerator (V70 D5 185) caused by fluctuating supply voltage due to a dirty fuse blade.

Try cleaning any fuses in the relevant circuit.

Keep at it and don't give way to despair!

It's got a new OE (but not Volvo branded) - I changed it to see if the low mileage Volvo branded unit was at fault, it wasn't and was as clean as a whistle inside.

I know what you are saying regarding fuses - but my finger of suspicion is pointing at the wiring to the pressure sensor as there is no strain relief (bad practise) and vide shows the current through the sensor to drop as the fault occurs. BUT, is this the cause or a symptom...