Thread: Fuel problem in 4bd1

grab yourself a bit of thin walled ally tubing (or steel but steel takes longer), bout 400mm long
mount it in a vice and just wiggle it back and forth... see what happens

the short version of the same experiment is cut a flat section out of an aluminum can about 1/2 an inch wide and 2 inches long. cut a nick in the middle of the long side and hold one side while you flick the other end back and forth.

well after doing some work have still failed to find a definite air leak.

I pressurised the tank by connecting the compressor to the breather inlet on the tank. No fuel leaked from anywhere. I retightened the a couple of connections. I took out the pickup, no crack there. However I discovered the linkage at the tank was crossthreaded some time in the past. Maybe this is the problem. Also the pickup has a kink at the bend.

that kink will be at least 50% of the problem...

if the fuel is restriced as the pumps while they are positive displacement the lift pump has no direct mechanical drive if it needs to stay in the non pump position it will. a Low pressure on the inlet is enough to do this..

Restrictions on the return side can also have some funny quirks to em, did you check those?

thanks again Dave. I will get the pick up repaired or replaced. L/Rover quoted $54 for a new one. I will check if a hose fitter can repair it.

I managed to prime it after fitting plumbing tape to the thread of the connection at the tank that is a bit damaged. It was better. However, when the motor started air bubbles were visible at the in-line filter (located immediately before the lift pump).

The tank is under the front seat. So the return is really short and straight. Can't see how there is a restriction there.

Originally Posted by rar110

thanks again Dave. I will get the pick up repaired or replaced. L/Rover quoted $54 for a new one. I will check if a hose fitter can repair it.

I managed to prime it after fitting plumbing tape to the thread of the connection at the tank that is a bit damaged. It was better. However, when the motor started air bubbles were visible at the in-line filter (located immediately before the lift pump).

The tank is under the front seat. So the return is really short and straight. Can't see how there is a restriction there.

A better temporary fix for the fitting (if you have time) is to get some diesel stable gaskget sealasitc (RTV black will do nicely) and coat the male fitting, filling the threads and a little more up to but not including the first 2 turns of thread. let that set for about 5 minutes while you remove,drain and blow out the pickup line.

Reassemble and then let sit for at least 8 hours before attempting to bleed.

just dont try to over tension it. your aiming to have the goop make the seal and the threads just do the mechanical holding.

Originally Posted by rar110

I think air is getting in some where. As I said I fitted an inline filter before the lift pump.

One of the diesel guys that I spoke to said that you don't put a filter on the draw side of a pump. Fine to fit it lower than the tank, say so gravity does the work for you. Could it be with your other problems, having the new filter on the draw side of the lift pump is making it all just a bit too much hard work for the lift pump.

Cheers
Simon

Yea it's not a real good idea to have a filter before the lift pump of a diesel. The reason they have a sediment bowel is because they don't create a resistance. Plus the lift pumps are designed to tolerate crap in the fuel, and the filter the Isuzu runs on the manifold is a pretty good one. If you do have the impulse to throw a different type of filter in, replace the unit on the manifold, don't add extra ones, especialy before the pump.
You could also try replacing the washers on the banjo bolts, as these are more often than not overlooked and are more often than not the problem. The banjo fitting only has to be a little twisted off center to create an air leak, and the rubber coated Isuzu fuel washers are a one use only item.

Never heard of the pick ups in the tanks cracking, new to me. Have seen people mixing the supply and return lines when re-plumbing, that leads to only having 3/4 of your tank usable.

Good luck though

the reason it happens and this is just an educated guess..

some of the army rovers have a wierdo gauze filter thing on the end of the pickup and the fuel sloshing against this wiggles the pipe, and leads to fatigue failures... Id suggest its probabley more common in the rovers that run around with about half a tank of dieso off road...

Ive been on 3 recoveries where a rover had died from lack of fuel but 2 jerries worth had diesel coming out the filler necks (army 110s have only 60ish l tanks