The prior article was dealing with a completely clogged pick-up pipe in the fuel tank. It is more common to have a partially restricted fuel flow that will allow enough fuel flow for the engine to run perfectly well up to a certain fuel flow, and then the engine will begin to falter. Slow down a bit and it will run well again. Drive up hill with heavier throttle setting, and the problem will occur at lower road speed. This is related to fuel consumption (power requirement), only indirectly related to road speed.

The fuel flow restriction may be a result of trash in the fuel system clogging up the pick-up pipe in the fuel tank. This may require removal of the fuel tank to repeatedly rinse it out to remove the dirt. In cases of severe rust in the tank, it may require replacement of the tank. It is not uncommon to find a dent in the bottom of the tank resulting in the tank bottom being pushed up against the open end of the fuel pick-up pipe to close the pipe entrance restricting fuel flow. Using air pressure in the tank may push out a dent in the bottom to clear the pick-up pipe, if the pipe itself was not damaged.

You may ultimately find dirt in a fuel screen in the fuel pump or at entrance to the float chamber on a carburetor, or dirt in the float chamber clogging a passage from the float chamber to the throttle body. Fix for this is to clean the fuel screens (three original in the MGA), and.or clean crud out of the float chambers.

There may otherwise be a kink in a metal pipe or a rubber hose, a rubber hose deteriorating to be collapsed and clogged internally. For MGA with standard SU H4 carburetors, rubber grommets between float chamber and throttle body may deteriorate and swell up resulting in clogging of the port in the attaching banjo bolt. Cure for these issues is to replace the damaged or deteriorated parts.

To check fuel flow, pull the fuel feed hose off the rear carb, and hold it in a catch vessel. Switch on and observe fuel flow. You should get a gusher, at lest one pint per minute. If not, look upstream for the feed problem. If you do get good fuel flow, look for some obstruction in the carburetor, like crud in the bottom of the float chamber, or perished rubber washers on the banjo bolt between float chamber and throttle body.

The Workshop Manual section D.6 describes a method (and tool) for more accurately measuring fuel flow with the commonly expected pressure head. Fuel delivery is specified to be 10 Gal/Hr Imperial, 12 Gal/Hr US, 45.4 Liter/Hr, 1.6-US pint/min, with 48-inches output lift (1.83-psi back pressure). No cheating on the fuel flow. If you don't have that much fuel flow, look for the restriction, or consider replacing the fuel pump.