Which fuel pump is faulty?

[jacques schiddt]

Hi folks!

Now and again, my car takes a few more cranks to get it started, than normal.
Once, it even started, then stopped and when it was re-started, was lumpy for about fifty feet but then got back to normal.

I suspect fuel feed, as the Under Bonnet Pump is sometimes noisy whilst priming (variosu whirrs and gurgles!) and I never have a problem starting the car, if I allow the pump about fifteen-twenty seconds to prime first.

I have put my ear to the fuel filler and can hear the In Tank Pump whirring and occasionaly I can hear the gurgling of liquid too (diesel, of course).

So, yeah...how do I decide if one of the pumps is faulty and if so, which one?

Many thanks,

JS.

[mh007]

I would suspect the under-bonnet pump if you say it's noisy.

When you say you've heard gurgling, was your fuel level quite low by any chance ?

Just another thought: when was the fuel filter last changed ?

[okenora]

if the car runs the UBP is working, though possibly not at 100%, the ITP could have failed but the UBP will keep things running, for a while at least

if the car refuses to start when under 1/4 a tank of diesel suspect the ITP, check for it running by listening at the filler flap.

[jacques schiddt]

Thanks folks. I have been keeping an eye on the fuel level, in relation to the (minor) starting issue and I'm not yet convinced that it's related to low fuel; it's been on less than a quarter full and it's started alright most of the time...although I'm not sure I've had any difficulties when it's been above a quarter full...hmmm.

Okenora, as I mentioned in my original message, I can hear the ITP whirring when I put my ear to the filler cap area, so it's definitely doing something. Should I assume, that because it's making a noise, it's working ok? (I'm guessing I should assume nothing).

mh007, I'm fairly confident that the fuel filter will have been changed at the last service and the next isn't due for at least 10k miles but maybe I should check it. As for the gurgling, the UBP has in the past, gurgled quite loudly, until (it seems) it's filled up and primed. As for the ITP, I can hear it whirring and it sounds like it's moving fluid because I can hear it making a "liquidy" sound, amidst the whirring.

Cheers,

JS.

[Mike Noc]

It could be a problem with the piping in the tank, as once the system has primed it should stay primed.

If the ITP has been changed in the past maybe the outlet pipe connection from the pump isn't fuel tight.