I had an urgent engine warning come on a few months back after a long drive 4+ hours (2004 XC70 diesel). I stopped and started and it went away
roll on 2-3 months and on another long drive, about 4 hours in, the engine cut and wouldn't start so I had to get recovered. About 4 days later the car was relayed from the recovery companys storage to my garage where it merrily started and drove off the truck.
Anyway, I plugged in my Chinese VIDA/DICE and read off ECM-2503, ECM-2505 low fuel pressure. On the advice of a local volvo indi, my garage replaced the fuel filter. The car has been driving ok the last week since getting it back but I've only done <2 hr drives and the mechanic said he thought there was a possibility that the lift pump in the tank was at fault because he couldn't hear it prime when turning the ignition on. I've kept it 1/2 tank full on the off chance it's lacking pressure and hopeful that a bid of head will help it.
I cleared the codes last week at the garage and the ECM codes haven't returned but thought I'd do some fault tracing today to see if I could see anything wrong.
I disconnected the power to the pump and tested the 2 thickest wires (black and blue) and got 12v continuous with ignition in position II.
I then checked for continuity across the same pins on the pump itself and got 4k ohms.
I have a few questions..
1. is that resistance correct or does it indicate a broken pump. I can't hear anything but a very very faint buzz with my head against the pump having removed the seat and access cover.
2. Having reassembled everything it did occur to me that I had only tested resistance one way - so it's possible if there's a diode in there that I should have tested different polarity - can anyone confirm?
3. Should the pump make an obvious noise...there certainly wasn't any obvious buzz or hum and whatever there was, was extremely faint.
3. is it even possible for the car to drive with a broken in-tank fuel pump?!
4. did I test the correct wires
Ant.