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Slow cranking when checking compression

2587 Views 4 Replies 5 Participants Last post by  rn240sx
The other day I thought I'd check the compression on my 98 4 banger. I followed the procedure in the manual, i.e. relieved and disabled the fuel system, pulled the control wire harness plug from the distributor and then continued to take out all four spark plugs. Threaded in the gauge adapter, put the pedal to the metal and turned the key. The problem was that the cranking speed was reduced to about one third of what it normally is. My compression readings were quite low, in the 130 psi range, which I attribute to the slow cranking speed. When putting everything back together, the engine cranked at normal speed and started just fine.
The funny thing is that the same thing happened when I checked compression on my 96 Honda Civic. Essentially the same procedure, disable fuel system and ignition, full throttle, turn key, and it cranked very slowly. Again, cranking speed returned to normal after the test.
Any idea why this happens and how to achieve normal cranking speed when checking compression?
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plug the dizzy back in and try again!
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