UK Car Repair Questions? Ask a Mechanic for Answers ASAP
1st thing to check is if the throttle is being opened when you are doing the compression test?
you don't say what year your 300C is but the later ones use a throttle on the intake to generate vacuum instead of running a pump
if there's no throttle and the compression test results are genuine then I'd repeat the compression test with some oil squirted into the bores as this will increase the pressure generated if the fault is with the piston rings
if the measurement stays the same then the fault is with the valve sealing
in that case its possible the rings are gummed up?
try some parafinn or redex into each bore and leave to soak for a few days
do you still need help?
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