Fuel Pump?

[stephen pook]

Like to pick your brains on one guys and gals.

Drove for about 40 miles yesterday and the engine cut out at idle without warning. Tried to restart the engine.. no joy. I noticed that there was no whiring from the fuel pump when turning the ignition key so I assume thats what the problem is. I had a play around with the connections etc but still nothing.I was meeting a mate and had things planned so luckily I found somewhere to leave it parked up. I returned to the car about 6 hours later with a view to arranging recovery but found it started (fuel pump was now whiring again). Drove for about a mile and concked out again. : No fuel pump noise. Two minutes later noise starts again and she started and I then drove 40 miles home without a problem!

Any ideas what would be causing this intermittent fault? I've looked at the obvious conections etc (although I'm not sure where thy all are). Is there a relay or a fuse connector that could be iffy or is it likely to need a new pump?

All suggestions welcombe as I've got next this off work and am a bit wary of driving too far in it for obvious reasons...

Thanks in advance,

Steve.

PS Its a V8S by the way.

[GreenV8S]

Lots of possible causes for that, and you will need to track them down methodically.

To start with I suggest you get a fused lead with a croc clip at one end and a female spade connector at the other to fit the fuel pump terminal, long enough to reach from the battery to the fuel pump. This enables you to bypass the normal fuel pump power supply and control system. It's invaluable to get you home in an emergency, and also helps show whether the problems you're having are just in the fuel pump control/supply circuit, or are more general electrical problems. Also, if it happens again see whether any of the other ignition switched circuits are working. The connection between the ignition switch and the main loom is notoriously unreliable and can cause these reliability problems, but will also take out the waning lights, radio etc so it is easy to spot. So, the hot wire will hopefully let you work out whether it's just a pump supply/control problem, or a more general problem. While you're at it, make sure you have some spare fuses and a couple of the Bosch metal cased relays used for the fuel pump and ECU main power, and go into the passenger footwell and make sure you can recognise the fuses and relay for the fuel pump.

Edited to add: the fuel pump terminal needs a bigger spade than normal, 8mm I think.

Edited by GreenV8S on Sunday 24th September 14:10

[stephen pook]

Thanks I'll try that. I suppose it could be a another problem entirely as I've just had a chat with a good motor engineer who commented that the fuel pump would only whirr in the event that the fuel pressure was low and if the engine had just stalled it is likely that the fuel pressure will remain adequately high for quite a while.

Oh well back to the drawing board...

[z_chromozone]

Pretty sure it will be the pump relay (usually a metal one). Buy a decent replacement from Range Rover, not a cheap pin number matched relay from your local motorfactor.

If that is not the case and you are driving around and it keeps cutting out take a length of wire and a blade fuse setup and just bridge the pump to the battery with the wire hanging out the boot. It will get you home.

Z

[GreenV8S]

stephen pook said:

had a chat with a good motor engineer who commented that the fuel pump would only whirr in the event that the fuel pressure was low and if the engine had just stalled it is likely that the fuel pressure will remain adequately high for quite a while.

Your good motor engineer should know better than to guess! He seems to think that the fuel pump only runs when the pressure is low, which used to be the case for some carb pumps but not normally for EFI cars and certainly not for this one. This system uses a pressure regulated return and the pump runs under the control of the ECU, there is no pressure sensing and it is not controlled based on fuel pressure. The algorithm is very simple: it runs it for a few seconds when you switch the ignition on, and continually while the engine is turning, and for a few seconds afterwards. If yours behaves differently, there's a fault.

[stephen pook]

OK, thanks for that guys.

Can you tell me where to locate the pump Relay and how I can identify it? I must get hold of a copy of the Bible!

Cheers,

Steve.

[GreenV8S]

stephen pook said:

Can you tell me where to locate the pump Relay and how I can identify it?

The fuel pump relay is one of two metal cased Bosch relays on flying leads close to the ECU, in the passenger's footwell. (The other one is the ECU main power relay.)