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MG TD TF 1500 - Auxiliary Fuel Pump

I would like to add an auxiliary electric fuel pump to my 53 TD. It would be controlled by a switch to operate only in the event of the SU failure. I am hesitant because I am not sure that a positive pressure pump could bypass the two internal disc valves in the stock SU pump. Since the SU works on a pulsating principle where each of the discs open alternately with the push-pull operation of the diaphram, how would the positive fuel flow from the aux pump get past the two disc valves in the SU? Seems like one disc or the other would stop the flow from getting to the carburetors.
Jim Merz

Jim,

There was a technical article in the latest issue of The Sacred Octagon (New England MGT Register) that describes the construction of an emergency fuel pump for MG-Ts. Essential, the pump is blood-pressure bulb attached to a rubber tube which is ultimately attached to a rubber stopper. In the event of fuel pump failure, the stopper is inserted into the gas tank filler (tight fit) and the blood-pressure bulb is pumped. This puts positive pressure into the gas tank which forces gasoline through the inoperative SU fuel pump. Obviously, some care must be used to avoid over-pressurizing the gas tank, which would send to much fuel and flood the carbs.

Anyway, the observation being that if that system works, then placing a backup fuel pump upstream from the stock SU (between the gas tank and the stock fuel pump) should work.

Larry
'51TD
Larry Thompson

Perhaps out of curiosity I duplicated the setup with twin fuel pumps as it was on the MK II: second fuel line from the tank, second pump. Moss sells the bracket for the extra pump. For my own enjoyment I added switches for each pump and LEDs that light up whenever one pump clicks - all hidden in the glove box of course! This allows me to watch the operation of both pumps. Incidentally no fuel flows in the line between the carburettors if both pumps are somewhat balanced! The extra advantage of thissetup is that in case of failure of one pump, the other one gets me home.

Denis
Denis L. Baggi

I installed a Moss electric pump back by my gas tank as a backup. I have run each pump independently and notice no differnce in performance. The Moss pump will push through the SU and the SU will pull through the Moss pump just fine. I normally run with the SU because I like the SU clicks and not the continuously running Moss pump. I also like to hear the SU shut off telling me I don't have an overflowing carb bowl.
Joe Holtslag

The two disks (valves) in the SU fuel pump serve only as check valves, so any pump can "pump through" the SU with no problem. Adding an auxiliary pump or carrying a spare pump is always a good idea, especially if you are going on a long trip. I modified my pump to solid state some 20 years ago and now have in excess of 90,000 miles on it with no problems, but I still carry a spare pump. Any of you who are interested in my SU fuel pump overhaul and solid state modification service, e-mail me direct at the above address and I'll send you a write up of the services.
David DuBois

This thread was discussed on 22/02/2000

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.