All MGB models used an SU electric fuel pump, mounted behind the heelboard on the right-hand side of the car, inboard of the forward rear spring hanger. The pump type changed several times during production, and an important consideration when ordering is whether the car uses a positive or negative earth electrical system.
Pump Types
The first pump type was fitted from the start of production in 1962 until August 1964. In August 1964, this was replaced by a pump with a redesigned body.
In February 1968, a further revised pump was introduced incorporating an additional breather fitted to the end cover. This type continued through to January 1977, when the final pump specification was introduced, identifiable by its end cover which is no longer stepped as on previous pumps.
The later pump offered improved contact life and was less liable to buzzing, and is fully interchangeable with the type it replaced. From the start of rubber bumper production in 1974, the pump mounting was revised so that the electrics end of the pump protruded into the boot, where it was protected by a black-painted metal cover.
This is a detail to be aware of when replacing a pump on a rubber bumper car, as the mounting arrangement and associated grommet differ from chrome bumper cars.
Earth Polarity
All GHN3 and GHD3 cars from 1962 to 1967 were originally positive earth, though many have since been converted to negative earth. All GHN4/GHD4 and GHN5/GHD5 cars from 1968 onwards are negative earth. It is essential to check the earth polarity of the car before ordering a replacement pump, as positive and negative earth pumps are not interchangeable. Both conventional points-type and electronic fuel pumps are available, electronic pumps eliminate the mechanical contact points that can wear and cause intermittent fuel starvation, offering improved reliability particularly on cars that are used regularly.
The mounting bracket, grommet, and fixings differ between chrome bumper and rubber bumper applications and are available separately. Pump inlet and outlet connections including olives, nuts, and elbows are available individually for replacing worn or damaged fittings.
Performance Fuel Pumps
For performance-oriented owners or those experiencing fuel starvation at higher engine speeds, a performance electric fuel pump is available. This sustains higher fuel pressure and flow than the standard SU pump, making it suited to modified engines or cars used in spirited driving. A performance pump must always be used with a fuel pressure regulator to ensure the carburettors are not overfuelled at idle and low speeds, and an in-line fuse holder is also required. Standard and performance fuel regulators are available, along with replacement filter elements for both types.