If your engine won’t start
easily when hot, and has good fuel delivery and good spark, it may be
because heat soak is making the fuel expand and rise enough to dribble
out the jet and flood the engine a bit. Although we haven’t struck it
with any of the Midgets, I have had this problem with my MGB. rubber auto oil seals
MG.In that case, it was so bad that between 30 seconds and 20 minutes
after switch-off it would not start with the starter regardless of
throttle position and had to be pushed. Every time! (So parking was
always on a handy hill wherever possible!) Outside of this time it
always started instantly.
In this case it was exacerbated by a combination of big bore engine, very high compression ratio and mild street cam, together putting a lot of load on the starter – and so dropping the battery voltage significantly.rubber auto oil seals MG.
The solution was multipronged:
Dropped the float level a little lower than spec to reduce the amount of flooding. (Having made this change I had to check that it didn’t it lean out under power of course)
Fitted a ballast resistor & ballasted coil so the coil now sees its full operating voltage when the starter is cranking.rubber auto oil seals MG.
Fitted a geared starter to reduce the current drain and therefore system voltage drop.
This completely solved the problem. The engine still floods a little, but with the starter spinning the engine better and the system voltage staying higher and so allowing a fatter spark at the plugs the engine now fires after half a dozen revolutions at worst – usually it’s instant.rubber auto oil seals MG.
There are other causes of hot start difficulty, to check whether the above is relevant to any difficulty you might be experiencing I would suggest that next time it happens you whip off the dashpot & piston from one of the carbs & see if any fuel is dribbling from the jet or (if not) if the fuel level in the jet is at the top and about to overflow. This should confirm or otherwise whether your car is affected in the same way.rubber auto oil seals MG.
If it is, before spending any money try the usual response to flooding of full throttle while cranking on the starter – if that overcomes it it’s a cheaper fix than what I had to do! And check the float level in the carbs – it may be just that it is higher than it should be.rubber auto oil seals MG.
In this case it was exacerbated by a combination of big bore engine, very high compression ratio and mild street cam, together putting a lot of load on the starter – and so dropping the battery voltage significantly.rubber auto oil seals MG.
The solution was multipronged:
Dropped the float level a little lower than spec to reduce the amount of flooding. (Having made this change I had to check that it didn’t it lean out under power of course)
Fitted a ballast resistor & ballasted coil so the coil now sees its full operating voltage when the starter is cranking.rubber auto oil seals MG.
Fitted a geared starter to reduce the current drain and therefore system voltage drop.
This completely solved the problem. The engine still floods a little, but with the starter spinning the engine better and the system voltage staying higher and so allowing a fatter spark at the plugs the engine now fires after half a dozen revolutions at worst – usually it’s instant.rubber auto oil seals MG.
There are other causes of hot start difficulty, to check whether the above is relevant to any difficulty you might be experiencing I would suggest that next time it happens you whip off the dashpot & piston from one of the carbs & see if any fuel is dribbling from the jet or (if not) if the fuel level in the jet is at the top and about to overflow. This should confirm or otherwise whether your car is affected in the same way.rubber auto oil seals MG.
If it is, before spending any money try the usual response to flooding of full throttle while cranking on the starter – if that overcomes it it’s a cheaper fix than what I had to do! And check the float level in the carbs – it may be just that it is higher than it should be.rubber auto oil seals MG.
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