Fuel supply operation/problem

[murfitt]

I have a 2001 XK8 that has had some issues with starting recently. sometimes it will not rev other times it will not start at all, and then after a few weeks of leaving it (after charging the battery) it started instantly. then i left it for a week and now it won't start again. i have checked whether fuel is getting to the fuel rail by opening the Schrader Valve and nothing comes out whether cranking it or not.

My main question is: when does the fuel pump operate? is it only when the engine is cranking or when the ignition is turned on?

Also what other reasons could create an intermittent fuel supply problem (other than a faulty pump) such as fuel filter? I have checked the fuses which are fine. Is there a simple way to check the pump without removing it?

i am not I wasn't getting any fault codes although now i am getting P1000. ECM internal error, but this maybe due to constant cranking perhaps.

Hopefully it isn't the ECM and hopefully it isn't the pump but i suspect that is what it will be.

I had a similar problem a year ago which i put down to low fuel level but i have a full tank this time.

Any suggestions gratefully received.

[mike020150]

Hi,
If you suspect a fuel problem, I'd recommend starting with the simplest things first. These are the fuel pump relay and the fuel filter. Substitute the relay and change the filter. Only if these actions fail to provide a cure, move to suspecting the more complicated (more expensive) possibilities, like the pump (which is inside the tank) or a wiring issue. Mike.

[murfitt]

well it turned out to be the fuel pump. i removed the relay and bypassed it to run the pump manually. the pump was drawing current but didnt seem to be running, well to be honest i couldn't tell so i removed the fuel filter anyway, which was fine so i tried the pump while the filter was disconnected, after a few goes it fired up. (collecting into a bowl i put under the car!)
so the conclusion is that the fuel pump seems to stick if it is not used for a couple of weeks (maybe days), don't know if these damp conditions we are having at the moment helps much. Seems to be fine once it is running though.
I will have to monitor it and see if it continues to be a problem, may have to replace it.

To answer my own original question: the pump fires up when you turn on the ignition not sure if it turns off once the pressure is up though. and useful to know that you can clearly hear the pump from the open boot, and a useful test that it is working is to remove the relay and put a wire across the switched contact. incidentally the power is permanently on (i.e. when ignition off) on the +12v side of the contact.

[mike020150]

Shame, it sounds expensive! Looking on the bright side, at least you have the option of checking to see if you can find a deal on a pump in your own time rather than being stranded by the roadside and having to pay full main dealer prices to get going again. Keep us posted on progress. Failed fuel pumps are not unknown and any info would be sure to benefit others. Mike.