MGB Fuelpump 74 MGB

[Mike W]

Im working on this barn find car new to forum and MGBs, anyway was checking fuel pressure@ 2.5 psi., with switch on, then did volume test, less then a quarter qt. I then checked the voltage to pump, and the voltage is pulsating 10v, and then nothing, like off and on every second, it also looks to be rewired because every one was talking about white wires to the pump where as mine are blue, is it suppose to pulse with key on and then when running speed up Im stumped on this, it will run and drive, but backfires and sputters in 4th gear, any help appreciated.

 

[DrEntropy]

Just some thoughts: Fuel starved. Sounds like somewhere in its past it got a "creative" rewiring of the pump. It should have a steady 12V from the ignition switch. If the car does not have an overdrive transmission, you could find the yellow wire under-dash and have half of your rewiring of the pump solved. BMC (and later British Leyland) made all harnesses with the yellow overdrive wire, whether the overdrive was fitted or not.

 

[Roger]

Does the MGB have a voltage stabiliser for gauges? Could the pump be wired from that, in error?

 

[Mike W]

Does the MGB have a voltage stabiliser for gauges? Could the pump be wired from that, in error?

That was where my mind was going too, I may just run a separate circuit with a switch and see what happens.