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MG MGB Technical - I've ruined my fuel pump

I used the pump (SU with points) to drain the fuel tank prior to some repairs. Now it only works whilst being thumped. The points look alright, so is there another obvious suspect component? I'd rather repair than replace as this is the third pump in six years.
Many thanks,
Steve
Steve Postins

Check the ground connection to the pump. Three pumps in six years seems very unusual.
John H

Thanks for the suggestion but I think I ruled that out a while ago when I ran a second earth to the body (otherwise it would have been four pumps in six years!). It's a daily driver so it's done some miles in that time but the pump's certainly a weak point.
Steve Postins

All of that clicking probably wore the points a bit
and the gap is a little beyond spec.

So...check the points gap.

I don't know the specs offhand, but it's in the
Robert Bentley book (along with the procedure
to adjust the points).
Daniel Wong

Steve - Daniel is correct, the points may have been worn a bit beyond their optimum adjustment. First clean the contacts well with 400 grit sand paper, then adjust the upper tank so that the upper points raise 0.035" above the top of the pedestal when the lower toggle is at the top of its throw, then adjust the lower tang for 0.075" - 0.090" (click on image below for picture of adjustments). That should get you going again. Cheers - Dave

David DuBois

Many thanks for that. Unfortunately, in my impatience I've stripped the thing and now have created another problem. Having separated the two halves of the pump body and spun the diaphragm a few times I can't set the armature correctly as the Haynes manual suggests. When I follow the instructions (hold horizontally, unscrew until armature is just thrown, unscrew some more) the armature is almost falling out and when reassembled it won't run. It will run whilst in half. Could you put me straight before I really ruin it please?
Steve Postins

I have been very happy with the transistorised pump.
Stan Best

This thread was discussed on 23/05/2007

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