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MG MGB Technical - ZS still running rich

The symptoms are:
1) Black soot particles mixed with water vapor showing up in wet spot on gargage floor when starting from cold. Just sooty smelling exhaust once engine warms.
2) Blackened plugs.
3) Idle drops and engine wants to stall when warm, unless I continue to give it some gas.
4) Hard warm starts.

What I have done so far:
1) Rebuilt carb last fall, switched to a Grose-jet at that time rather then the regular needle valve. Adjusted the float to the proper height.
2) Disassembled the manuel choke last month, cleaned and replaced the o-rings in it.
3) Replaced the air idle regulator with a new one.
4) Adjusted the metering needle all the way anti clockwise. It has a 45H needle.

Question: I not sure what the purpose of the float is. If it is sticking or the grose-jet or needle valve is not shutting properly will the cause the engine to run rich? If so, what is the best way to check if this is the problem?

What I plan to do:
1) Change the metering needle to a 45M since I live at high altitude.
2) Check the air piston diaphram for any tears while I have it out.
3) Check the float. Maybe switch back to the needle valve.
4) Rebuild my charcoal absorbtion cannisters since I have never had them open.

Is there anything I am missing? Would the absortion cannisters have any effect on rich running, or would I be wasting my time there?

Any advice would be greatly appreciated. It is time for me to go for emissions test again and I could only imagine what the results would be in this rich running conditon.

Thanks,
John '79B
John F

Ok, richness problem seems to be fixed,(engine is idling smooth now). I replaced the metering needle with the leanest one available, 45M. I also eliminated a vaccume leak at the brake servo and most important I discovered that the idle changed(increased) when I disconnected the hose going to the absorption canister. Leading me to believe there may be a problem with pressurization of the ELS (Thanks to an aricle on ZS by John Twist). I am assuming it will be ok to run with this hose(to the cannister)not connected.
The main question I still have is can anyone recommend the best fuel additive I can use to help brake up, and help flush out the carbon that has built up in the engine? I have replaced the plugs. Are there any fuel additive products that should be avoided?
Thanks,
John
John F

This thread was discussed on 29/11/2002

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