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-   -   Run Up drops of 140-200 RPMs (http://www.vansairforce.com/community/showthread.php?t=176185)

n518jh 10-20-2019 02:43 PM

Run Up drops of 140-200 RPMs
 
Lately I have been having trouble starting my RV-12 (2009 Engine delivery). My mechanic seems to think it is bad Ignition Modules. I had a soft start since the beginning, now 400 hrs. The current soft start went bad (didn't start when installed, started when disconnected.)

In the last set of start ups, the drops when A only or B only were 200 and 130 respectively. Would that support the thought of bad ignition modules, or should something else be tried before ordering new? Help please, those new modules are apparently expensive. Mark 518JH

NinerBikes 10-20-2019 04:36 PM

If it starts and runs, and then at 4000 rpms, you are seeing those kind of rpm drops instead of 80 to 90 rpm, for each, I would suspect something in the ignition system. Go through each item in the ignition system, one by one, until you eliminate the problem.

Capacitors, condensers, spark plug wires, and new plugs are where I would first check. Last would be ignition modules.

Piper J3 10-20-2019 06:16 PM

Maybe this... http://www.vansairforce.com/communit...park+plug+caps

RFSchaller 10-20-2019 10:22 PM

As I recall ROTAX allows up to 300 RPM drop with a delta of 115 RPM, so your numbers would be within limits, but in almost 1000 hours and 7 years I have never seen greater than 100 RPM drop and a delta of 50 RPM.

n518jh 10-21-2019 11:29 PM

Erratic starting and large RPM drop
 
I will take your advices. Thanks. Will report on progress. The non start is the biggest problem.On advice I ran a hair dryer on the ignition modules and coils for about a minute, and the engine started, after several non start tries. Does that indicate anything? Once started it will restart with no problem.

Another comment was the in the 2005-8 years, a number of ignition modules were shipped that eventually caused non-start problems. Anyone have information on that perspective (my engine shipped in 2009), Mark

JBPILOT 10-22-2019 06:46 AM

I ordered my kit day one
 
I had both ign modules fail between 400 - 500 hours. Back then they had a program where they would sell you two new YELLOW strip ones for much less than normal retail. Have 1,370 hours now. Not a problem again.

Cammie Patch 10-22-2019 01:54 PM

Those RPM drops are normal. At 4000, the engine is at it's leanest position. In the summer you will get less RPM drop, since the combustion is happier. In the winter, it would prefer more fuel, thus the higher drop.

Mag drop issues tend to point to carburetor issues more than ignition issues overall.

NinerBikes 10-22-2019 08:04 PM

Quote:

Originally Posted by Cammie Patch (Post 1381341)
Those RPM drops are normal. At 4000, the engine is at it's leanest position. In the summer you will get less RPM drop, since the combustion is happier. In the winter, it would prefer more fuel, thus the higher drop.

Mag drop issues tend to point to carburetor issues more than ignition issues overall.

Too lean, generally, or too rich?

Clean the air filters and check the color of the spark plugs? Rebuild the carbs? Thoughts?


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