Magnetos

U2Hoog · Post by **U2Hoog** » Mon Sep 29, 2003 1:19 am

I'm having a transient vibration in my engine. Some days it runs smooth as silk, other days I have this odd vibration that I can't seem to get rid of, no matter the mixture or rpm settings. My A&P tells me that it is almost certainly a mag or ignition harness problem.

Any thoughts? Also, what about replacement mags? Any newer products that have STC's for replacing the old mags?

Hoog

N170BP · Post by **N170BP** » Mon Sep 29, 2003 4:27 am

Try cleaning or replacing your spark plugs before you
spring for a set of mags.

The plugs can test fine in a tester (under pressure) but
the testers I've seen cannot apply the pressure / heat /
stress the plugs are exposed to during cruise flight.

I had a plug going in and out (working, then not) in the
air. All 12 tested fine on the ground. Bought a new set
of plugs, and.... presto....

Bela P. Havasreti
'54 C-170B N170BP

zero.one.victor · Post by **zero.one.victor** » Tue Sep 30, 2003 5:07 am

Ditto Bela's comments re: plug replacement. Look in the logbooks & try to figure how many hours on yours. Last spring,my airplane REFUSED to start--I tore into the mags as it appeared to be a weak spark problem. Mags were OK,I then replaced the plugs which had about 450 hours on them and looked & tested OK--that did the trick! I found the Alison/Autolite plugs to be cheaper by a couple bucks each. But they need a deeper socket than do the champions,what I saved on plugs I ended up spending on a deeper (1/2" drive) deep socket.

Eric

U2Hoog · Post by **U2Hoog** » Tue Sep 30, 2003 5:36 am

I asked the A&P about that (plugs), and he said we replaced them not this year, but last. So only about 100 hours on the plugs. We're going flying tomorrow to see what he thinks too.

FredM · Post by **FredM** » Wed Oct 01, 2003 6:48 am

What does your A&P say about testing your ignition harness with a high tension lead tester? I wouldn't completely rule out the plugs either even though you only have 100 hours on them.

U2Hoog · Post by **U2Hoog** » Wed Oct 01, 2003 3:57 pm

Hey, that's a good point too! We went flying yesterday, and he acknowledges the transient, so it's not just a figment of my imagination (you know, the autorough that happens the minute you are over terrain where there's no really suitable place to put her down in a pinch). So, we're into the troubleshooting phase big time.

Thanks.

The International Cessna 170 Association

Magnetos

Magnetos

Plugs

I'll ask!