Talk Morgan Forums Community Vehicle Talk (non-Morgan) Air in fuel supply

I’m hoping someone can guide me here. I’m working on my mate’s Series 2 Land Rover, it has a supplementary fuel (petrol) filter before the carb, this is the transparent disposable type, lying horizontal. Air bubbles enter the filter until it is empty although there is enough flow to keep the engine running. I’ve filled it with a syringe but it slowly empties. I’ve replaced the petrol hose, remade the joints and fitted new clamps on the suction to the pump. The mechanical pump diaphragm seems intact and it pumps ok with the priming lever.
I’m working on the basis that any leaks on the discharge side of the pump would leak petrol not suck air.
Is it possible air is entering the pump somewhere? It is the type with a glass filter bowl on the side of the casting.
Any help or ideas would be gratefully received!
Chris

Sounds as though fuel may be draining back into the tank?
Is there a non return valve in the fuel line?

Air is coming through with the engine running Graham, though it seems to be getting enough petrol to run ok. Got me beat!

Interesting. I had to ask that question (from a previous motor).
If all pipework from tank to filter is OK I'd suggest a pinhole in the lift pipe in the tank. Do you get air if the tank is completely full (as in part way up the filler, so above tank top)?

Is there a reserve valve

I wondered that and hoped it would stop when the tank was brimmed but it didn't. I've removed the lift pipe and it looks ok, I'll try running it with the end of the 'plastic' suction pipe immersed directly in the tank.
I appreciate your help Graham, I knew I would get a response on here, a lot of Morgan owners seem to run Landys also, strange that!
Chris

Perhaps a silly question, but has it always done this?

Not silly at all Graham, it was reluctant to start and wouldn't idle, I got involved and cleaned up the SU carburettor which fixed it but then noticed the empty filter. The owner is non-technical and can't confirm if it's always pushed air through. I guess that as long as enough petrol is getting to the float chamber in the carb it will run, it doesn't display symptoms of fuel starvation at high revs. Bit hard to tell when an old 2.2 petrol Landy is down on power!
I don't see any air bubbles in the glass bowl of the filter on the pump but it's not easy to from above.

If it's running OK now I wouldn't worry.
I'm pretty sure the filter on my '76 4/4 did not remain full. Don't think it ever appeared to be full, either. Check the casing on the plastic filter though, mine went soft after a few years and I decided to replace every couple of years after that - at under 5k miles p.a. it never clogged up.
Fuel certainly drained back to the tank after a couple of days - but the extra cranking (mechanical pump) for a cold start meant a little more oil circulation before the engine fired.

My first LR was a '66 IIa with a low compression petrol as far as we could ascertain - pulled better than the 2.3 diesel though

I've just given it a test run and foot to the floor in top it wouldn't go over 35 so defo fuel starvation at high demand.
I removed the hose connection to the lift tube and immersed it in a jar of petrol and the engine ran without drawing air, so I suspect the lift tube but it looks fine and I can't work out a way to pressure test it because of the mesh soldered on the bottom. Before I order a new one I'm going to replace the old plastic fuel tube with a continuous length of new ethanol proof tubing (not happy with the plastic to rubber inserted joint anyway), and test by dropping this straight in the tank. That should finally eliminate the problem. At least it's all easily accessible in an old Land Rover!
Thanks again, Chris