fuel pump

[chiparus]

any advice please.
I have a 3.8 roadster that blows the fuse very randomly which supplies voltage to the fuel pump.
Firstly, can anyone tell me the correct value of fuse ?
The handbook says 5 amp, fuse F4, or bottom left fuse with dash dropped down.
When it first blew , I removed a 35 amp fuse and replaced with same, this has blown again and again, anywhere, anytime, engine hot or cold.
I have monitored the current drawn on tickover and it is less than 1 amp, constant.
The pump is in the tank and of the " whirring " noise type, though I know little more than that.
I use Shell v power fuel ,if that makes a difference to how the pump functions, but the car is so unreliable now , I cannot risk using it.
Any advice would be greatly appreciated.
Thanks
Kevin Shaw.

[piman]

Hello Kevin,

the most likely cause is the wire feeding the pump has chafed through and is intermittently shorting. I would try and trace the wire from the pump itself until it goes back into the loom to see if there is any evidence of this? If that section is sound then it must be in the loom itself somewhere? They can be difficult to find so an alternative is to run a new wire from the fuse to the pump but this is rather a stop gap measure.

Alec

[stuarthardy]

Hi Kevin

The fuel pump should have fuse No 4 all to itself. I say this because people can hijack supplies for other purposes. You should have only 2 wires connected to Fuse 4, a white (which in turn connects to fuse 6) and a white/purple, which connects directly to your fuel pump. This wire runs through the left hand body harness, along the LH sill, through the diaphragm behind the LH door and into the boot area where it connects to the fuel pump via a rubber connector block fitted to the front panel of the spare wheel well. I would start at this connector to check for any dodgy connections or shorting to earth. You should ensure that the correct rating of fuse is used when you finally sort this problem out as it is likely that someone has fitted the higher rated fuse as it stopped the problem, temporarily. Unfortunately, electrical problems don't heal themselves with time.

I can't remember the precise configuration because I replaced my immersed pump with a remote one, similar to the 4.2 E-Type. I did this because the standard pump is considered to be unreliable and incapable of delivering sufficient fuel when you start pressing on.

I think the wiring to the pump passes through a tube via a sealing gland and can chafe against the tube (don't worry, its not in the presence of petrol vapour). You may need to pull the pump to check for this. You might be quite surprised at the state of the pump when you see it!

Regards

[chiparus]

Thanks for advice, I have started to trace the feed cable, white/purple , from pump through to fuse, the cable itself is encapsulated in a hessian material all the way through the car.
I think I will disconnect at both ends, run a temporary cable, and try car to see if problem is cured.
Failing that I may come back for advice on pump removal from tank.

Thanks again
Kevin.