Engine: D5: V70 D5 - Low fuel pressure in 4th and 6th gear?

[Infiltrator]

Got us baffled this one..
Red warning on the dash, 6 codes, 2 glow plug relay, 2 air sensor, can't remember the 5th one, but the red warning is low fuel pressure. Reset all the warnings and they quickly return when driving the car. In 4th gear and 6th gear it feels like a misfire, all other gears drive fine. Using a live code detector as soon as the misfire occurs the low fuel pressure code and red warning appear?

I can't think of anything that would be common to only 4th and 6th gear that would be linked to fuel pressure?

Anyone know what might be causing this?

Only thing in the back of my mind is that we recently had a parasitic battery drain which was caused by some corrosion on a circuit board in the body control module which in turn was leaving the ABS system powered up, the auto electrician cleaned the board up as best as he could but said we might encounter other electrical gremlins in the future. The ABS battery drain was resolved by bypassing the body control module and using a feed direct from the ignition.

But regardless of the body control module fault I still can't think of anything fuel related that would only impact 4th and 6th, thanks.

[Lancee]

Fuel filter ?

[Simmy]

alternator low revs in higher gears less alternator speed less voltage to fuel pump lower pressure

[Infiltrator]

Originally Posted by Lancee

Fuel filter ?

Changed just over a year ago, so ruled this out.

[Infiltrator]

Originally Posted by Simmy

alternator low revs in higher gears less alternator speed less voltage to fuel pump lower pressure

Yes, but it drives fine in 5th gear?

[Simmy]

try another new fuel filter and scan with vida to view live data and an injector test. by passing electrical component is not a great idea why did you not fix it the correct way?

[Infiltrator]

Originally Posted by Simmy

try another new fuel filter and scan with vida to view live data and an injector test. by passing electrical component is not a great idea why did you not fix it the correct way?

Cars not worth much, it's my son's car and he really doesn't need a diesel estate any more, it's costing him too much to run without these issues! correct way would have meant a replacement body control unit. If I can't sort it myself cheaply it'll probably be sold or broken. Planning to swap out the injectors this weekend, I have a good spare one, and will try changing the filter too, thanks.

[Lancee]

Might not be worth much but a shame to lose another one. These are inherently very good cars.

[Simmy]

look for a crashed donor car plenty available on salvage sites . if they crashed they were running and driveing then you have unlimited parts for cheap.it might get you a few more years with the old car . i see keeping an old car going as a chalenge good luck and keep us posted.

[Infiltrator]

My own car is a 56 plate Saab Aero wagon with 180k miles, it's just had a front subframe, clutch and alternator, plus some restoration welding - one attention hungry temperamental Swede in the household is enough!

See how we get on with it.