MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Engine will not stay running

I had a blown head gasket which I replaced on my 77 MGB. Since I replaced the head gasket the car will not stay running!! The visible problem is “the engine is getting too much gas into the manifold and is stalling/flooding out. The following actions have been taken with no real change in the situation:
Compression check shows all in specification and within 5 lbs. pressure between all, the distributor has been replaced as well as the CEI unit (OEM parts), getting strong spark all around, The carburetor has been replaced with a new OEM carb, no change in starting and running, I have replaced the fuel pump using OEM parts, vacuum lines are hooked up correctly and seem to be in spec, timing is in spec. the rockers were adjusted to spec before I replaced the valve cover, the head bolts were all torqued to 55 lbs. With all that has been changed/adjusted the car should be running now!! I have no idea what to do next!! All I can think to do is take the head off and start over!!

Help will be greatly appreciated!!

Thanks,
Jim McDowell

Jim,

Even a new carb needs to be set up. Have you checked to make sure the float and needle are stopping the flow of gas when the float bowl is full? All it takes is a tiny bit of gunk to make it stick open, and repairs frequently cause tiny bits of gunk to come loose. Also, check to make sure the water-actuated choke is adjusted fully counterclockwise and that it is functioning properly, i.e. staying closed when it is supposed to. The metering needle may be adjusted too rich as well. In the Moss catalog, there is a neat little tuning guide for the Z-S carb by John Twist. If you need more detail, Haynes has a manual on carbs that covers SU's, Zenith-Stromberg, and Weber carbs and also has the SU needle chart.
Paul Konkle

Thanks for your in-put. I thought it might be the bowl but on two different carbs? The one I took off had been working fine before I replaced the head gasket. The new one did not change the problem in any way. I don't think the carb is the problem.

Jim
Jim McDowell

Is the OEM carb the Zenith 175CD? If so, I agree with
Pault that the autochoke
may be sticking on. One way to check if no problem is obvious
is to remove the
authochoke assembly and tape over the exposed holes in
the main carb body.

I bought a replacement autochoke and found it had not
been assembled properly at the factory (the metering
needle housing was not oriented properly.) You may have to
disassemble the autochoke and figure out what's going on.

Also try Paul's suggestions for adjusting the choke.
Ronald

Jim,

Do I understand correctly that you have the same problem with both old and new carburetors? If so, then maybe your new fuel pump is generating too much pressure. I think in your shoes I'd put a pressure guage on the line and see what's going on there.

Matt Kulka

Ron- Yes the carb is a 175CD. I reset the auto chock on the first carb and checked the setting on the new one. No difference in performance!

Matt- The original fuel pump was installed when I tried both the old an new carbs. The new pump was installed and used with the new carb. No difference in performance!

Jim

Jim McDowell

Have you double checked to make sure the manifold gasket is on properly and that you do not have
have vacuum leaks? With good compression I wouldn't think you would gain anything by removing the
head again. Clifton
Clifton Gordon

This thread was discussed on 18/04/2002

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.