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MG MGB Technical - Trouble starting when warm (69MGB)

Typically when my '69 is warm, I have trouble starting it. It will crank and crank until it runs the battery down. If I push it just a little or are on a slight hill and "pop the clutch", it starts instantly. Any ideas?
Fred Mihaylo

I had a similar problem with my '69 several weeks ago. It would crank and crank but would not fire off. I never tried to push start it so I don't know if this would have worked or not. The only difference between push starting and cranking is that when you push start the car you typicaly engage first gear, if the car is rolling at 5mph, that is the equivalent of about 1000 RPMs. Perhaps the engine spinning at a higher rate helps it to suck in more fuel. To solve my problem, I actualy leaned the engine way out,(the problem arose after the carbs were richened ALOT by my father who wasn't paying much attention). After I leaned out the carbs the warm starting improved 100 percent. Good luck.
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Robert

Sounds like the timing could be slightly off. Try retarding it slightly.
Luis

How old is the coil?

If you have points/condenser, when was the last time you changed the condenser?

I would lean towards electrical in the ignition.
glg gimbut

Possibly flooding due to heat soak and carb float level(s)being set too high? Does the car run a little rough and emit black smoke for a few moments after you bump start it?
Andrew Blackley

If it will start instantly when roll-starting, it's not a fuel problem -- I'm with glg, it sounds electrical to me. My gut instinct is a marginal ignition coil... Strong enough to start the car when given full voltage, but not so when the starter drags the voltage down.
Rob Edwards

Thanks for the responses. In answer to some of the questions; I believe the coil is original and it's been a while since I changed the points and condenser (I drive the car seldom). As far a smoking, it doesn't. When "popping the clutch", the car only has to be slightly moving. I can also try leaning out the carbs, but can't understand if this is the cause, why it starts so easily by pushing it.!!??
Fred Mihaylo

I'm with Rob. Check the spark while cranking. It's possible the condenser has failed giving a weak spark. You should be able to hold the coil lead about 1/2" or more away from the coil and get a blue spark and a sharp 'crack'. If the condenser has failed it will barely jump a plug gap, be yellow, and make a 'fizzing' sound. I wouldn't touch the carbs yet - remember "most carb problems are caused by Lucas electrics".
Paul Hunt

Had the same problem with my 72. Installed pertronix electronic ignition and reset timing. (very easy install by the way). Instant improvement!
Dan H.
Dan Hanson

Slightly off topic, but I have the exact same problem with a 1985 Kawasaki Vulcan.

When running the starter, the spark is white hot and will jump a half inch gap, so weak electrics don't seem the problem. On the other hand, the starter on that bike does not spin the motor very fast. (Whatever happened to kick starters?) I spoke to a Kawasaki mechanic. He felt it was low compression, but I haven't taken the time to verify that yet. Fred, it wouldn't take much time to run a compression test on your car to rule that out.

Matt Kulka

If you brought it to my shop, [when it was still operational] the first thing I would do is a basic tune-up. check compression, adjust valves, new plugs, Pertronix are excellent, with their coil. You can't expect a 40 year old car, especially a LBC,. to live that long without attention. Replace the fuel filter. Check fuel pump pressure and volume. Change or clean the air filters. And 'fer cryin' out loud, change the oil and filter.
You will have alot less problem with any car with regular maintenance.
Dwight McCullough

Oops.
Forgot to talk about batteries, and connections. Also starter draw. But start with the battery, Are the connections clean and tight? I mean really? does it have water/electrolyte above the plates? You can have a connection problem even when they look clean. Polish them! Then if still having a problem, get a shop to test the battery and starter draw.
Dwight McCullough

I too go with electrical. The fact the car starts right off when "jump started" tells me the ignition is effected by the voltage drop due to the the starter motor operation. Have a look at your secondary coil wires as well as your other usual suspect ignition components. Time and mileage are not on our side when it comes to these old cars :>{)

Good luck and let us know what the outcome is. It benefits us all to learn from these experiences.

cheers

Gary
gary n. hansen

Had a '52 Hudson with the same problem...needed a valve job. Junked the car (that was in 1961)...was only worth $25 or so back then...wish I had it now.....
R. L Carleen

Sounds Like the points have closed up or the distributor shaft bushings are shot causeing the points to close try opening the original points before you replace them Ric
RicN

This thread was discussed between 28/03/2003 and 29/03/2003

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