Compression check- you are looking for reasonable compression readings , and also importantly readings that are within 5- 7 lbs from each other. You really can not tell from the thumb method. The thumb method tells you if you have little or no compression. If you do not have a compression gauge and buy one make sure you it has an adapter that fits the A spark plug hole, a lot/most plugs are metric and supplied adapters do not fit.
The procedure is not difficult, if you search I am sure there is info in the forum. Or if you have a mechanic friend he may have a gauge and can help you. Or pay a local independent shop to do and possibly teach you. Just be aware when performing the test the spark lever must be fully up/retarded and all plugs should be removed.
From your symptoms you have a too rich condition fouling all your plugs, kind of points to a carb issue since it is affecting all cylinders (all plugs black). If running so rich that it stalls in a couple of minutes and you have to clean plugs the problem is pretty intense. If you had an intake manifold issue it would suck air and run lean.
Others that know the fuel system better than me will have to comment.
I am unsure how/why a carb would run rich unless you have an air filter plugged, or the carb is messed up. Could be you have a clogged passage in the carb. newer carb, but you never know when something can get through, or if the carb/fuel sat a long time something varnished up.
Quote:
Originally Posted by alexiskai
OK, I'll try to take these responses in turn:
- Gas cap: I did make sure the gas cap was venting. Fuel flow is good down to the carburetor.
- Modern distributor: Yes, it is the modern points and wireless plates. I've had trouble with them before, but I looked them over pretty thoroughly this time and can't see any problems.
- Condenser: Could be the condenser, but then why does the spark test good every time I check it? I checked it with the engine off and on. I guess I can't be certain it's working 100% of the time.
- Fouled plugs: I treated the plugs with a wire brush after I pulled them and found them to be fouled. Should I do more?
- Compression check: Do I need a tool for this or can I check it by just sticking a thumb in the plug socket and turning the engine over?
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