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MGB My 1st MGB - coughing after 10 minutes

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Petizo

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Hello everyone, I am very excited. I got delivered tonight my fist 1977 MG MGB.
I had test drove it twice the first time i drove it around the block and it was great. The second time I brought a friend with me, he has a 1975 midget to check it out. We found that a few minutes into our drive, the car started kind of coughing. We check with the seller and he said that it never happen to him before. Any way I fell in love with the card and bought it.
It was delivered tonight, a beautiful dark green with tan top and interior. I drove it and it ran great. When my wife came home we drove it again. and sure enough after a little while started kind of coughing. I have figured that it happens once it warms up. Also I noticed that once you turn it off, it looks like it keeps going like for a second or two. This only happens once is warm. Does anyone have a clue what can cause this. I am new at this very excited and willing to learn.

Thanks

Jorge
 
Welcome.
Check to see that your fuel filter is clean. There may be an extra in-line fuel filter near the electric fuel (in front of the rear axle). A plugged filter will cause coughing due to lean fuel mixture
Also tighten the intake manifold bolts if they seem loose (a loose manifold may create a vacuum leak that can also cause a lean mixture).
There are many, many other possiblities....I'm just giving you a few obvious and easy fixes to try first
You did not mention a workshop manual....that's the first thing you should buy if you don't have one.
 
thanks, I will try that. I am in the process of ordering a manual on ebay as we speak.

Thanks for the tip. I will post the results.

J.
 
Jorge,

I agreee on the stumble, quite likely a fuel delivery problem.. I had to replace my fuel pump to fix unfortunately, Now I have a filter before the pump!!

Not sure on yoru model, but on my California Model ''77 there is an 'anti run-on' valve mounted on teh firewall, just in front of the evap canister. there is a tube that runs from it to the intake manifold.

when the oil pressure drops ( engine stops ) it is supposed to open, allowing fresh air into the intake manifold, to prevent the run-on or 'dieseling' that you are experiencing.

this part is available from Mossmotors.com if you find that it is not opening.

Better get familiar with a test light and a multimeter.

And congratulations on your 'new' MGB
 
Hi if the car is coughing or spitting? it meanns that it is running too lean. the run on may be caused by the ignition being too advanced. This is a common problem to stromberg carberetted MGBS.
 
I am not sure, it does not happen all the time. If you are running for a while and then get to a stop, the "coughing" starts when you start again, for a few seconds then it goes away. It does not happen when you are driving at speed.
My friend has a midget and he suggested I check the carburator to see if it need it oil, it was not empty but it need it a bit, so I topped it off. While I was fiddling with the carburator I noticed that it was leaking a bit of gas from the bottom. The float chamber plug seemed lose you can twist it around with no resistance, I just do not know now what is the norm for that. I got myself a manual as suggested earlier. The diagram shows that there is an o-ring there. Can that be replace by itself? If so do you just pop it out? it did not seem to have any threads?

I am having a good time. I keep reading the manual (haynes) . I find it fascinating that this little machine is 27 years old and still works.

Thank you for your postings

Jorge
 
Jorge
you should fix that fuel leak as soon as you can because the exhaust pipe runs under the carb. The plug on the float bowl is held in by little plastic prongs, just pull on it with pliers. Once it is out the o ring is easy to replace.
Warren
 
Hello Jorge,

I had the same occurence with the frost plug at the bottom of the carb (Z-S) bowl leaking it can be easily fixed by replacing the seal washer and a gentle tap on the plug to seal it..

I agree that must be fixed. Also if your carb is short on oil in the dash pot coming off idle will be a bit of a problem.

Also check the state of the battery cable to body connector at the battery compartment. I doubt that is part of this problem tho.

Cheers
 
Hi,

I have one last thought, if you have the original Zenith Stromberg Carb, then it might be that the auto choke, if not converted to manual, is sticking in the on position. The auto choke is not known for reliability. This would then cause a stumble. For details on how to fix, check out the website for University Motors and ask them to e-mail you a copy of how to work on this carb. Mine has been converted to a manual choke and works somewhat well at present.

Best of luck.
 
Thank you for all the fine advice. I have already fix the carburator leak, by replacing the o-ring. I found that the hose that goes from the crank case and suppose to go to the carburator was disconnected. Once plugged in the car will stall so I adjusted the idling and voila no more staling. Also with a seringe I removed all the oil in the carb and added automatic transmission fluid, I spoke with a mechanic in a local shop where I am able to buy parts and he suggested to use that instead of motor oil, the manuals that i got said to use oil. Anyways it is running pretty smooth now. Although this weekend I got a bit of that coughing nothing compared with before.

Thanks for all the advice.
 
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