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MG MGB Technical - Fuel pump air-lines.

The original S.U. fuel pump on my '66 GT has two nipples for air-lines, one on the pump body the other on the plastic points cap. Where should the other end of these hoses terminate?
David Werblow

The one on the plastic cap should have a plastic lid on it, with a check ball inside. It vents the points to atmosphere to help cool them and the check ball prevents water from entering the fuel pump. The vent on the other end connects to a plastic line that runs inside of the car and terminates in a tee fitting. This provides a vacuum/pressure relief for the pump's diaphragm. If their's no lid on the plastic cover, another hose can be run from it into the inside of the vehicle to prevent the points from becoming fouled by water and other debris. RAY
rjm RAY

David - Ray is mostly correct - see the article, SU Fuel Pump Vents in the SU Fuel Pump Articles section of my Homepage at: http://homepages.donobi.net/sufuelpumps/. The spigot at bottom of the coil housing should be routed into the trunk using some 1/4" tubing (it can be tubing for a fish tank or the tubing that is used for drip watering systems) and a 'T' fitted on the end of the tubing to keep it from pulling out of the trunk. The vent on the end cover may have a cap on it or a spigot. Either way, there is a check valve inside the vent that only allow air to pass out of the area under the end cover, but not in. There is no need to run a tube from that vent to anywhere else. Cheers - Dave
David DuBois

Many thanks,gentlemen
David Werblow

I think that I can say this with some authority as I am an original
owner of a '71 MGB/GT (no previous owner that fiddled with
anything).

It is correct in that the vent hose at the base of the coil was routed into the trunk (boot) and ended in a "T" fitting. This was a clear
nylon hose (similar to pet fish aquarium air hose)

On my car, there was a hose attached to the barb on the points
end cap. This hose was long and loose and was tied to the right
side axle near the plastic axle breather and ended in a "T" fitting.
This was a black plastic hose that used a miniature version of a
fuel line hose clamp (not a worm screw clamp).

As production line methods changed every now and then
what is exactly correct sometimes becomes a loose and
slippery affair and so this may be found to differ from
car-to-car.
Daniel Wong

Both ports were run to the boot/trunk on chrome bumper cars, but at different heights, and using different-sized Tee fittings on the end for some reason. For rubber bumper only the pump body one has a plastic tube into the boot as the electrics end is already there.
PaulH Solihull

This thread was discussed between 19/04/2013 and 21/04/2013

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