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MG MGB Technical - Strange But True

Strange but true,

I was driving my 1976 MGBGT home late one evening when I was just about to pull off the road and noticed that the engine had died. She had been running fine up until that point (5 miles of a 6 mile journey). I tried starting her again but she wouldn’t have any of it. I walked my partner home and returned an hour later with a fellow MG owner. My MG still wouldn’t start. I checked the fuel by pulling off the pipe leading to the carburettors and there was plenty coming through. I have often had trouble with condensers so always keep a spare or three and changed this over, still no luck. I removed the first spark plug and checked the spark, this was fine, she still wouldn’t start, I removed the air filters and tried again, nothing. I then took off the petrol pipe feeding the carburettors, turned on the ignition and poured a little petrol down each carburettor (about 10ml) and tried starting her again. She coughed and spluttered and burst into life. I drove her home and she seemed fine.

Has anyone any idea what may be causing this?

It has been suggested that the MGB is getting upset after the arrival of the MGA that I am restoring and after seeing me rebuild the carburettors on the MGA it just got jealous?
Garreth

I experienced a very similar problem in a 74 GT, on three occasions. After the third time, I replaced both carb float needles; problem seems to have gone away.
Willie L.

I had a similar problem that plagued me for weeks. It turned out to be a lump of dirt blocking the metal inlet pipe on one of the float bowl lids. It would bounce around until it stopped the car somewhere, fall back out of the way after much cursing and cranking of the engine, and then do it all again a few miles later. Changing the fuel lines and float inlet needles didn't help me because of blockage being between the two. In short, I think you are right about the MGA rivalry.
Steve Postins

Just a thought. Could you have experienced a vapour lock in the fuel system?

JR
JR Ross

Next time it happens, if it happens, rap gently on the float bowls. Strange that both would stick simultaneously. Are you sure you don't have a clogged filter?

Mike
Mike Phillips

There are two current feeds to the ignition system. One runs through a resistance and is about 6 volts. The other comes off the starter relay and is twelve volts. When starting, 12 volts is sent to the 6 volt coil to enhance cold weather starting. The coil can handle the 12 volts for a short periond of time. Once running, when the ignition key is released, the 12 volt source is cut off and the ignition system runs on 6 volts. The switching is handled by the start and run positions of the ignition switch. You may have a bad ignition switch or the wiring circuit for the run position may need attention.
Blake

Blake,

Thanks for that, I replaced the ignition switch about 18 months ago when the old one started sticking. I'd also had problems in the past with the starter relay and replaced that. I think next time it happens it may be a case of tapping the relays, and teh float chambers to see if anyrhing happens.
Garreth

Blake - that problem allows the car to start but it dies again as soon as the key is returned from 'start' to 'run'.
Paul Hunt

This thread was discussed between 22/04/2003 and 29/04/2003

MG MGB Technical index

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