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blank cyl #4 column on engine monitor

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Well-Known Member
Jan 30, 2011
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Anyone have an idea why my JPI-700 engine monitor would read zero (blank column) at any low idle power 1100 or less with the mixture leaned. However, at full rich the bar EGT bar is higher than the other bars and when I re-lean it goes back to zero (no EGT or CHT readings). At run-up, climb and cruise and decent all temps (EGT/CHT) are equal across all 6 cylinders. This has been like this for a few months. I think it is the probes, which we will swap and test next. The AME verified all exhaust and cylinders were fairly equal temps using an external temp gauge. All cylinders also good compression, all plugs cleaned.

This is a PA32-300 1971 Cherokee six with 200 hours on the engine. It runs smooth otherwise.

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