What controls the stopping and starting of a V8 D1 fuel pump?

**Utemad** · 22nd April 2007, 09:37 AM

Hi all,

I had my very first genuine Land Rover break down/electrical fault yesterday

Although what better place to have it than Blknight's driveway?

The circumstances were that I drove 40mins to his place.
Parked out front.
Moved into his driveway to winch his Hills Hoist concrete out of the ground and did winch it out.
Moved out of driveway and back to street.
Moved back into driveway to winch more concrete out of ground.
After connecting all the chain etc went to start the Disco and it ran like crap.

So that is the story and this is what we found.
The fuel pump was not pumping. Fuse wasn't blown so found the relay and it wasn't clicking in and out. So we shorted out the relay and the fuel pump ran and the car would start. So the control circuit is at fault.

To get home I just shorted the relay.

This morning I shorted the relay again to drive into the driveway to fix the problem. When in the driveway I put the relay back in and could hear the pump! So all is well. (By shorting relay I mean remove relay and replace with two spade connectors connected with wire).

Problem being I am not silly enough to think that it is fixed just because it works again.

Has anyone else had this happen?
Do you know what causes it?
Do you know what controls the fuel pump?
The control wires are blue/purple and white/green.

I couldn't find a definitive wiring diagram on the RAVE CD.

Thanks for reading such a long post. I feel that all the info was relevant to get a broader picture

**PhilipA** · 22nd April 2007, 11:09 AM

Did you try another relay????
The ECU controls the relay , so wish that it's the relay.

ECU will activate relay for 10 secs on ign on, then shut off while cranking.
Relay reenergised as soon as ECU detects revs at running , I think 450 RPM.
Most likely to be the relay as it is mechanical, andcan have contacts burn.
Regards Philip A

**Utemad** · 22nd April 2007, 11:13 AM

Tested exisitng relay and tried another relay. Definately not the relay.

I was worried it was ECU controlled.

I'll hope for a loose wire. Otherwise I'll just connect it to 'ON' power.

**discowhite** · 22nd April 2007, 12:51 PM

mine did the same thing on many occasions, first it was a dead fuel pump, then it was a bad earth at the fuel pump/sender cap
then after all that the +ive wire actually broke in the tank!

i went through countless amounts of relays b4 i found the problems.

cheers phil

**Utemad** · 22nd April 2007, 01:35 PM

Originally Posted by discowhite

mine did the same thing on many occasions, first it was a dead fuel pump, then it was a bad earth at the fuel pump/sender cap
then after all that the +ive wire actually broke in the tank!

Cool more things to look forward too!
However mine is definately a control issue. Still working fine though.

**Blknight.aus** · 22nd April 2007, 06:18 PM

I'll back him on the control feed to the relay being the problem...

we did the relay substitute thing on the driveway and the kick the fuel tank thing.

My suspect is a loose connection between the exu and the relay base.

mcrover · 22nd April 2007, 06:49 PM

Im not all that proficient in this area but could it be a faulty preasure reg or blocked filter as both could make the pump shut off when it gets up to pressure.

I would put a 'T' in before the first filter and monitor the pressure, if pressure drops then it's pump if it doesnt then it's not the pump.

**Utemad** · 22nd April 2007, 07:47 PM

Originally Posted by mcrover

Im not all that proficient in this area but could it be a faulty preasure reg or blocked filter as both could make the pump shut off when it gets up to pressure.

I would put a 'T' in before the first filter and monitor the pressure, if pressure drops then it's pump if it doesnt then it's not the pump.

It is definately not the pump. If I short out the relay then the pump and engine run sweet.

I'll bash around in the general area of the relay and see if I can cause a fault. It has to be a loose connection on the control side of things. Then again maybe I should leave it alone and hope for the best.

**Utemad** · 24th April 2007, 10:01 PM

Well this is an interesting turn of events.

On Saturday I had the aforementioned control problem and tonight my fuel pump died.

My car wouldn't start and gave the same symptoms as before but this time when I swapped the relay for the jumper the car still wouldn't start.

So I pulled everything out of the back of my car which was of course packed to the roof with stuff to come home from work

. This included pulling the cargo drawers out. Then off with the pump cover and find there is indeed power to the pump. Then I pulled the pump out and put power directly to the motor and nothing happened. So dead pump.

After having read this just this week I now get to put it into practice.
http://www.aulro.com/afvb/showthread...ight=fuel+pump

I tried pulling the motor apart but all I managed to do was crack the top cover. So think I'll just try and get the Bosch pump on Thursday and hitch a lift back to work.

This seems to be a coincidence to have two fuel system failures in one week but I can't help but think that somehow they are related. Just don't sensibly know how.

mcrover · 25th April 2007, 10:23 AM

I would say that the pump was the problem all the time and it was burning contacts in the relays due to excess amp's pulled because of a faulty pump.

By bypassing the relay you are bypassing the contacts and the fixed wire can handle more amperage than the relay contacts so it would cover up the high current draw.

If it happens to someone else check the current draw and it might help if someone posts current draw of a healthy pump to try and diagnose this easier in the future.

Just what I recon

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