I have a 1977 Mg Midget that wont start. The engine turns over and sputters for a few seconds and then stops.
I removed the 4th spark plug, and placed a ground wire to it from the engine block to see if I would get a spark, which I did, and also the engine started.
I then thought there might be a bad ground to the engine, so I used a jumper cable to ground it to the frame, and place the spark plug back into the engine, and tried to restart the engine. The engine would not start again. Any thoughts?
Since the engine sputters and started when you removed and grounded the plug, it seems that the ignition system would have to be working, although you may want to throw a scope on the plug wires and see what the voltage spikes look like.
What have you checked in the fuel delivery system? Does the accelerator pump spray? If so, there’s gas in the float bowl, if not you may want to check that out.
What did the plug look like? was it wet? If so, your float may be sunk, your needle valve staying open, and your fuel delivery flooding the cylinders.
The float and valve together keep the level of the float bowl just right so the lateral wall pressure in the venturi draws in the air as a realatively vaporized stream. If the float has sunk the valve will stay open and the fuel line pressure will push fluid gas through the orafice in the ventui. Fluid gas won’t run the engine, only vaporized gas.
Post back with what you find.
I am voting for the float valve. The accelerator pump may be supplying just enough fuel to do that almost start thing.
Thank you for your response.
Thought about this for a while, and tested the other plugs, and they had a spark.
Apart from testing the plug for spark, it also releases pressure from the engine.
I unbolted the exhaust pipe after the catalytic converter, and saw a little water come out in doing so, but my thought was perhaps a critter made a nest somewhere in the exhaust line, or the converter may have corroded and be partially blocked.
After that she started right up!
Now I have to go spelunking for the critter!