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Farmall Tractors Discussion Board |
Re: Super M runs rough
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Posted by jw on February 10, 1999 at 09:09:33:
In Reply to: Super M runs rough posted by Dave P on February 10, 1999 at 04:40:32:
Try putting a vacuum gauge on it. There should be a plug right above where the carb bolts on. If the vacuum reads steady from 17-22 in Hg, that is normal. If it is low and steady, it has late ignition timing, valve timing, or low compression. If it is very low (5-6 or so) there is a vacuum leak. Check gaskets between carb and manifold, and manifold to head. If the needle fluctuates as engine speed increases, there is an ignition miss, blown head gasket, or leaking valve or weak valve springs. If there is a gradual drop in reading at idle, the exhaust systems is plugged. If there is an intermittent fluctuation, there may be an ignition miss or sticking valve. Check plug wires. If the needle just drifts up or down, the idle mixture on the carb is not set right, or there may be a minor intake leak. If it is high and steady, the ignition timing is too far advanced. A vacuum gauge is relatively cheap, and is a good tool to use to check a number of problems as you can see.
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