abnranger69
Member
I have a Lycoming O-320 on my RV 4 that has decided to run on only two cylinders. I would have thought that virtually impossible to happen. Especially both being cold/dead on the (same) left side. It?s a carbureted/aspirated, mid-time engine. Shut off with mags a couple weeks ago to check ground. Exhaust is two pipes w/crossover. No recent maint done/changes before last flight. Fuel sumped.
Flew it in just fine, never skipped a beat, left it outside in average weather for a few days, went to start it up one morning and shook like after normal easy start. Knew I was in uncharted territory by the sound it was making. Tried running it up to 1000-1200 RPM thinking a fowled plug, leaned it, cycled mags with 30-40 drop each side. Shut it down after 1-2 min thinking She never gives me any trouble.
Took it over to maint shop, removed the cowl, started up again with same results and tests for the A&P. No backfiring.
Both left cylinders dead cold, hot on R side. Trouble shooting included the obvious:
Good visual insp, nothing noted
Removed, cleaned, gapped, tested plugs. One failed at 120 PSI. All were normal color, no excessive deposits or wear. Replaced. Nothing out of ordinary noted looking into the cylinders.
Again, started up, tried various mixture settings, etc? Same results
Compressions checked, mid 70s all around.
Valve covers removed, pulled prop through all cyl, valves moved appropriately. So nothing sticking open/closed.
Tested each plug wire, visible spark noted from each one while grounding it out.
Mags checked/opened up. One shaft/bushing with some sloppiness. Removed and sent out for a 500hr insp/check. No visible arc/carbon pattern noted that would maybe indicate a cross firing.
Didn?t pull the air filter (round K&M with wire mesh inside/outside element) So no rats could get in and plug two left intakes (reaching here I know}
Sooooo, I?m open to any suggestions from all the experts out there. I?m stumped.
Feel free to throw out some less obvious trouble shooting suggestions. Just not making any sense to me
Will compile and start over when mags get back in a couple weeks. Personally, I don?t think it?s the mags??.
Thanx all.
Dave
[email protected]
Flew it in just fine, never skipped a beat, left it outside in average weather for a few days, went to start it up one morning and shook like after normal easy start. Knew I was in uncharted territory by the sound it was making. Tried running it up to 1000-1200 RPM thinking a fowled plug, leaned it, cycled mags with 30-40 drop each side. Shut it down after 1-2 min thinking She never gives me any trouble.
Took it over to maint shop, removed the cowl, started up again with same results and tests for the A&P. No backfiring.
Both left cylinders dead cold, hot on R side. Trouble shooting included the obvious:
Good visual insp, nothing noted
Removed, cleaned, gapped, tested plugs. One failed at 120 PSI. All were normal color, no excessive deposits or wear. Replaced. Nothing out of ordinary noted looking into the cylinders.
Again, started up, tried various mixture settings, etc? Same results
Compressions checked, mid 70s all around.
Valve covers removed, pulled prop through all cyl, valves moved appropriately. So nothing sticking open/closed.
Tested each plug wire, visible spark noted from each one while grounding it out.
Mags checked/opened up. One shaft/bushing with some sloppiness. Removed and sent out for a 500hr insp/check. No visible arc/carbon pattern noted that would maybe indicate a cross firing.
Didn?t pull the air filter (round K&M with wire mesh inside/outside element) So no rats could get in and plug two left intakes (reaching here I know}
Sooooo, I?m open to any suggestions from all the experts out there. I?m stumped.
Feel free to throw out some less obvious trouble shooting suggestions. Just not making any sense to me
Will compile and start over when mags get back in a couple weeks. Personally, I don?t think it?s the mags??.
Thanx all.
Dave
[email protected]
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