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MG MGB Technical - New fuel pump doesn't work right

A few weeks ago my '77B died on the road. After checking a few things I realized that it wasn't getting any fuel, even though I could hear the fuel pump pumping like crazy. I (wrongly) thought that the diaphram in the pump was holed since it was clearly pumping very fast with no results. So I bought a new Standard SU pump. While installing the new pump, the hose from the gas tank came off in pieces. (lesson learned) Well, I figured that at least now I have a good spare pump, and continued to install the new one. After a couple of outings amounting to maybe 50 miles, the car started to miss occationally, got quickly worse, died, recovered, then died for good. No gas and no pumping. Assuming the new pump should be good, I checked out the wiring and found enough problems to warrent replacing all wires involved. After confirming good connections and power to thepump, the pump would only give 2 or 3 cycles when powered up and then stop, even with the fuel line from the carb open. To eliminate a clogged line question, I loosened both fuel lines right at the pump. Same results. Finally I put the old one back in and that worked, and continues to work perfectly. One last check with the new pump in hand and no hoses attached, and it cycled freely as long as I wanted. Any ideas on what is going on with this thing? I want to fix it correctly, put it in the car and have the old one as a spare.

Thanks for any insight,
Mark
Mark Rotsky

Mark,

Have you checked the condition of the tank? When I got the GT, I also replaced the fuel pump, as it was pumping very little fuel to the carbs. When the new one didn't pump either, I discovered the tank had silted/rusted up and completely plugged the intake screen. Even compressed air at 120 psi couldn't clear it. New gas tank and problem solved.
Paul Konkle

Mark - Your new pump is probably not adjusted correctly if it will run with no load on it, but not when loaded (hooked up to pump fuel). I would recommend talking to the outfit you purchased the pump from and see if they will replace it, since it is useless as it is. If they will not replace it for you, I can repair it and make it work correctly. IF you will e mail me directly, I'll send you a write up of my SU fuel pump services and a fuel delivery troubleshooting guide. Good luck - Dave
David DuBois

This thread was discussed on 02/10/2001

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