Outer Limits 4x4 Board

I have a 1984 Range Rover that has been fitted with a 97 model Discovery 3.9 fuel injected motor, which is duel fuel.

The problem I am having is that the motor will run fine on LPG but the second I turn it over to Petrol it sounds as though it is running on about 4 cylinders, but has a lot of un-burnt fuel coming out the exhaust.

The fact that the car runs well on LPG means that the car has both good compression and good spark.

By the process of elimination I have come down to it being a fuel related problem. When I turn the ignition on the fuel pump starts normally, but soon slows and begins to really labor. If however I disconnect the fuel line after the fuel filter the pump runs flat out, and fuel comes flying out. While having the ignition on I have disconnected the return line to the fuel tank to find only a tiny dribble returning to the tank, even though the fuel pump is laboring. When I disconnect the regulator from the fuel rail, the pump still runs flat out and fuel pours out of the rail.

My question is whether there is a chance that the fuel regulator has blocked. I think this is maybe quiet likely as that I have not been driven the car in ages and is nearly always driven on LPG.

Does anyone know what pressure the fuel should be in the fuel rail so I can check this as well?

Thanks for you help.

Hi,

First thing I would look at is the return line to the tank. They get blocked by rust etc in the little metal pipe at the front of the tank.

I found that compressed air was not enough to clear it properly and ended up using a piece of wire.

I have disconnected the fuel return line from the regulator, and with the ignition on there is only tiny drops coming out of the regulator, even though the fuel pump is laboring.

How was the efi setup ? 84 is pre efi so you either used RR efi tank/pump lines or a home made system ?

2.5 Bar ish, somewhere around there, sounds like your pump is fuggled and not getting to relief pressure..............or your fuel filter is blocked

All the injection setup is out of a Discovery, and the pump is located inside a long range tank.

Fuel filter isn't blocked.

Checked the pressure in the fuel rail and only looks to be about 2.2 - 2.3 bar. Once motor is attempting to run on petrol pressure fluctuates from 2.2 - 2.3 bar to under 2 bar.

Looks like I will bolt in another fuel pump and see if this fixes the problem.

Cheers