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MG MGB Technical - Fuel Pump?

Hi,

i seem to have a strange problem on my 71 BGT. Very occasionally my engine seems to struggle & then die, a bit like it's running out of petrol. This happens maybe once on a jounery & the car usually starts straight after. I suspect maybe a bad earth to the fuel pump. I would have thought if this had been an ignition problem the engine would die pretty much striaght away.

Any other ideas anyone?

Cheers

Scott
Scott Ralph

Try cleaning the points on your fuel pump.
Rob.
robert bryan

Scott: You are right, if it was an ignition problem usually the tach goes to zero imediately. If it was a fuel pump problem as the carbs run dry the engine will struggle and then die. But after the pump somehow comes back to life you will hear it clicking rapidly as the fuel lines and float bowls refill. Is this happening? If so then the pump is suspect. If need be run a temporary ground using a piece of new wire with an alligator clip. If the problem goes away you will know why.
However a grounding problem would not behave quite as you describe. It would not cure itself just by waiting. The waiting period would allow something to either cool down, or for excess pressure or vacuum to be relieved. If the line from the pump to the petrol tank was replaced with a rubber hose this could be collapsing, and then expanding after the pump suction is gone. Or the pump is trying to work too hard against a blockage in the delievry line. So check for blocked filter screens at the pump and replace the fuel filter under the bonnet, if you have one. If you remove the pump, then check the pump points. If you have already gone that far, you would be advised to have a rebuild kit handy and rebuild the pump whilst its out and in your hands.
Another possibility includes a blocked fuel cap vent. If you loosen the cap when the cars dies and you hear a "whoosh", then replace the cap.
Cheers, Andy
Andrew Blackley


SU fuel pump how I hate thee, let me count the ways.
Honestly, I think the MG reputation for unreiability is entirely due to this awful antique. I've had the thing to pieces and adjusted it and sanded and adjusted points and replaced points (SIXTY DOLLARS A SET !!!!!)and wound it's diaphram in and out the required turns (plus back one quater). And I don't think you could find a more awkward place to put it.
The final straw came when the SU pump refused to work on the West Gate bridge here in Melbourne, and ONLY on that bridge. Every where elso in town, over hill over dale, just fine. But on the west gate bridge ( a place you REALLY don't want to be stranded on believe me) it would die, usually after I had crested the top (the first three times,Not the last 2 alas) so I could coast over, then it would run fine.
I have now ruthlessly bypassed the wretched thing (the pump, not the bridge) and am using the electric pump from a '83 SUBRU (I happened to have). This works better, faster and WAY more reliably than the SU. It sits loosly wrapped in a peice of foam rubber in that dead space in top of the guard/engine compartment on the passenger side, could have been desighned for it. It's easy to install, you just poke it in there,and you can't even see it)There's no chance it will move so no bolts required. The wire you want is one of the white ones from the fuse box. I've got a fuel filter before the pump.
Truely Scott the SU fuel pump is the work of the devil.
Peter

This thread was discussed between 21/05/2002 and 22/05/2002

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