Thread: Fuel Feed Problem

Sounds like you have contaminants (sand, rust,water)in the float bowl.
You will have to take the carb off, remove the bowl and see if there are anything in there that shouldn't be.
If you find rust (very fine red particles) or sand they will more than likely be coming from the fuel tank.
To check that remove the seat box panel above the tank, and then remove the sender unit. Shine a torch inside to see if the same contaminants are in there as well.
If they are it's tank out, steam or high pressure water clean, dry and then coat the inside of the tank to seal it.
Very common problem with older vehicles that have stood for long periods of time.
Regards,

Could be as suggested, but I suspect it is not the carburetter, as the 'running normally' bit makes this less likely - dirt in the carburetter tends to be something that remains blocking a jet or passage once it is doing that.

Most likely is a restriction to fuel supply, which will be probably (since you have a new pump) not the pump. However, it could be an air leak on the suction side of the pump, or possibly the water trap screen filled with rust from the tank (as suggested, this is a likely source of fuel blockages). But it could also be from an air leak somewhere further back, and a most likely spot is a tiny rust hole in the suction pipe that dips into the tank, or the screen on the bottom of this blocked by debris in the tank.

Fuel starvation symptoms can also be mimicked in some cases by ignition faults, most likely either the points nearly closed up, or the coil becoming faulty as it warms up.

John

When mine did this (problem solved exactly the same way) it was the Zenith carburetor's warped body allowing air to leak past the big gasket that joins the two halves together. I overhauled the carby including re-facing the mating surfaces using wet and dry on a sheet of plate glass, and the problem went away.

Coop

First step, change the fuel filter. Even if it's new, change it. If it was old and it fixes the problem, it's probably just been picking up rubbish over the years. If it's new, and changing it fixes the problem, you've got rust and stuff coming in from the tank. If it doesn't fix the problem, well, filters are cheap and it's something you now KNOW is correct.

That's the problem with fuel filters, they just get full of rubbish and stop the fuel getting to the carby Mind you, that's their job.

You put a new fuel pump in a month ago. Did you muck up something there? Wouldn't hurt to check everything, including making sure it's pumping fuel (check when it stops, but don't spurt fuel all over the hot exhaust unless you love excitement). Someone suggested an air leak so check the hoses connected to the pump - loose fitting, split, ruddy great hole.

After those two, it's carby time as suggested. Seeing you haven't done up the carby, it wouldn't hurt to buy a kit and do it up anyway, there's something very satisfying in working on carbies and if you lay everything out in order as you remove them, not very difficult.

My second MGB (twin SUs) went from 12mpg and impossible to tune to mid 20s with a carby kit. The impossible to tune was cured by fixing the worn butterfly shaft bearings.

When I overhauled my carby- first time I'd ever pulled one apart- I had the big green manual right in front of me, and the digital camera at my side, and I photographed everything I did as I took it apart and laid it out. Certainly made the re-assembly very straightforward...

Coop