3.9l V8 lpg non starter, please help!

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Digforvictory07

New Member
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Location
Cornwall
Hi all, it's a long time since I've posted on a landy forum, but my 1999 Discovery 2 has me throwing myself at the feet of the Internet gods, please show mercy and help a wretched soul.

Bought a few months ago it has been (within reason) faultless, no engine troubles to speak of although it has always taken a few cranks to fire up it has never failed until now.

Switching off after a rainy drive the vehicle will not start. It fires over, and almost runs for a second, then stalls out. After getting it into the garage I'm three days in and still at a loss.

I believe it is electrical and potentially a bad earth, but have had no luck in finding it.
I have checked all fuses in the engine fuse box with a multimeter as well as the operation of the relays, and here's where it gets wierd.

The fuel pump relay is only getting 6.5v across the control contacts. Assuming one of relay control contacts should be earth and the other a switch live (which I've proved, and is giving 12v to battery earth with the ignition on). If I bridge the fuel pump relay, the fuel pump operates fine, however the engine still will not start and cuts out almost straight away.

I have also jerry-rigged an earth for the relay, which makes it operate fine, but the engine still will not take.

There is another component, an in-line fuel isolator (type of thing) that is fitted on a pipe that runs from the intake manifold to the 'EVAP canister'(see arrowed in pics). This component is also getting the strange 6.5v between its contacts (but 12v from its +ve to battery earth). This was not fixed by my jerry-rigged earth at the fuel relay, which makes me think they don't go to a common point.

The other anomaly (possible red-herring?) is a faint buzzing/ticking noise coming from the ABS relay, the air suspension up/down relay and also the ABS pump whilst the ignition is off. I think they are buzzing because their relay control earths are actually reading 3-4v (to battery earth, see pics). If the 30a ABS fuse is removed, that voltage dissappears, but it does not affect the fuel pump relay issue. I have noticed that occasionally it stops of its own accord (it can run for hours) but turning the ignition on again will set it back off.
I'm guessing this isn't normal?

I have been working on checking every earth point I can find (engine bay and footwells), but all seem to be fine. I've checked every fuse I can think of in the engine bay and drivers footwell to no avail. There is no sign of any corrosion or water ingress to the ECU or passenger footwell electronics, after 3 days in a dry workshop the issue still remains.

Could it be an issue with the LPG wiring? It feels like a needle in a haystack at the moment. When will this madness end? Arghh, Save me Jebus!

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Day 4, I think I've pinned it down to the ECU. The wire that should be supplying the fuel solenoid with a switched earth is actually supplying a switched 5.4v, with zero continuity to earth when the ignition is on.

Could this be anything to do with an immobiliser issue? I've not had any symptoms with the alarm or keyfob door locking but I'm not really sure how an immobiliser issue would present itself.
 
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