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Fuel pump problems on 1990 range rover auto 3.9 efi

I am having problems with an intermittent fuel pump. When I turn on the ignition I cannot hear the fuel pump and it won't start. It has been converted to LPG and will start on LPG but it revs constantly at about

2500 - 3000rpm.

I decided to try and drive the vehicle like this. On the first occasion the revs dropped down to normal tickover within half a mile, the fuel pump had started and it ran perfectly on petrol. I stopped the engine and it restarted normally. I assumed that this could be a sticking fuel pump and this may have cleared the problem.

The next day I started it and it did exactly the same again: Could not hear the fuel pump, it would not start on petrol and revved at 2500 -

3000rpm on LPG. I drove it again but this time it took over 3 miles before it returned to normal.

I am curious as to how the 2 issues are related i.e. high revving on LPG and broken fuel pump. Is it a function of the ECU to pick up the revs if it senses a problem with the fuel system?

What could be at fault here? I would normally look at the Fuel Pump but I replaced this 2 years ago and it has done less than 10,000 miles. Could it be the Fuel pump relay?

Any help would be greatly appreciated. Thanks.

Reply to
krusty1977
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I'm not sure if the two issues are related, but Discovery Efi's the pump will run for about 5 seconds, and will then switch off until the "engine running" signal is sent from the alternator. I assume the RR has a similar set-up, though I can't say for sure.

So, it could be that for whatever reason the engine run lead from the alternator is messing about.

Not a whole lot of use, but it may explain why the pump appears not to be running.

Richard

Reply to
beamendsltd

In news: snipped-for-privacy@m7g2000cwm.googlegroups.com, krusty1977 wittered on forthwith;

One of mine did similar things for a while. In the end I used to carry a bit of wire in the cubby which I'd use to take a live from any live fuse to the fuel pump fuse - just for a second - if it wouldn't start. Seemed ok after that, might play up once a month or so.

Reply to
Pete M

Assuming the LPG kit is a multipoint one, how does it get its feeds for running and doing all its stuff? does it piggy back off the petrol ecu and/or injectors? So presumably a problem with whichever of these it uses would also transfer itself over to the LPG system?

Reply to
Tom Woods

I don't know how your system (original and on petrol) relates to the earlier c 1988 3.5 but that required either the air flow meter switch to be closed (i.e. engine running and sucking air) or the ignition key in the 'start' (cranking) position for the pump to run. There is also the overrun cutoff relay (mounted near the LH suspension tower on RHD) which is prone to problems with corroded/broken connections.

How much of that system remains intact after the gas has been added I've no idea.

I've got some pdf material related to that vintage of fuel system if you want to see if any of it looks relevant.

Reply to
Dougal

It turns out that this was the fuel pump relay. I replaced this and it has been fine ever since. It must be a function of the ECU to pick up the engine revs if it detects a problem in the fuel system.

krusty1977 wrote:

Reply to
krusty1977

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