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.

In message <[email protected]>
"krusty1977" <[email protected]> wrote:

> 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.
>

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

--
www.beamends-lrspares.co.uk [email protected]
www.radioparadise.com - Good Music, No Vine
Lib Dems - Townies keeping comedy alive

In news:[email protected],
krusty1977 <[email protected]> wittered on forthwith;
> 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.

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.


--
Pete M - Using the Scouse Side of the Force -
Range Rover Vogue EFI
Citroën Xantia SX TD
OMF#9

"Stay calm. Stay calm. I'm a relatively respectable citizen -- a multiple
felon, perhaps, but certainly not dangerous."

On 27 Sep 2006 02:52:57 -0700, "krusty1977"
<[email protected]> wrote:

>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?

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?

>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?

krusty1977 wrote:

> 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.

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.

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:
> 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.