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MG MGB Technical - Fuel Pump Orientation

Does anyone know if the orientation of the SU electronic fuel pump is important. I had mine set-up (after having to move it to the location beside the battery box due to suspension mods on my 79 MGB) with the top/out line inverted (on the bottom) and seemed to be having intermittant fuel delivery (the car would suddenly die on trips of approximatley 15-20 miles and restart after a cool down period)problems which I had never experienced before and have since inverted it back right side up and as of yet the problem has not recurred. Just checkiing to see if anyone else has seen a similar problem. David DuBois are you out there?
Frank

Frank - very important that the outlet be on top, for the simple reason that air bubbles rise. If you get any air in your pump, for whatever reason - vapor lock, sucking dry on a hard turn, or a leak in the input hose connections, it will never be ejected from the pumping chamber, but will fill up the chamber with air and drastically reduce the pumping capacity. Kind of like the old detective stories where a hospital patient was killed by injecting air into his veins <sardonic grin>.

So, you were running out of fuel (in the carburettors), even if you had a full tank!

Air in the fuel lines past the pump isn't good, but it isn't fatal, either. It will merely flow past the needle valve into the carburettor float chamber, and be ejected into the atmosphere via the overflow ports.

Glad you got it sorted - - Alec
Alec Darnall

Frank - I believe that Alec pretty well explained the situation. there it a reason that the pumps have the word TOP right by the outlet port. No harm done to the pump though. Cheers - Dave
David DuBois

Thanks guys for the responses...these were my thoughts exactly. BTW..David during my fiddling with my pump I misplaced the small BB in the vent on the elctronic end of the pump....how critical is this and can you recommend a source for replcement if needed.
Frank

Frank - the size of the BB is 0.125" (1/8"). Cheers - Dave
David DuBois

This thread was discussed between 07/06/2006 and 08/06/2006

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