Re: Compression Testing
you have to run the motor with the plugs grounded or it wont run
. what they mean by grounding the plugs is controlling the spark. as your cranking the engine it creates ign spark. also you will have a fuel air mix that is about right for burning blowing out the plug holes. spark is spark wheather its inside or outside the combustion chamber, I have seen a few fires due to sparkplug wires dangling about while compression testing, its worse with EFI engines and engines that use an automatic enrichment circuit. on most 95 up OMC/BRP kill switches it will spark with the key in the start or run position and the flywheel turning. that only goes for the keyswicth mounted lanyards. best to either use a spark tester while testing compression, kills two birds with one stone. or jump the start solinoid with the key off or use a wire from each cap to ground.<br /> and even if you dont light the system on fire its hard on some of the more delicate parts to generate that much voltage and not control it.
