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MVVS 26cc gas won't run anymore

Old 09-25-2006, 10:02 AM
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Default MVVS 26cc gas won't run anymore

My MVVS 26 cc has been running great until yesterday when I spent 44 minutes flipping and tinkering to find out why this normally easy to start engine was acting up.

It fires for about a second after choking then quits with a puff of gas spraying out of the carb. Sometimes it backfires with a pop but the prop doesn't kick back when I flip it.

additional info:

1. Carb chokes easily because the hole in choke plate is soldered shut.

2. I emptied the gas tank to make sure I wasn't flooding it and tried to start it by priming the carb.

3. Tried a fresh batch of fuel.

4. Visual inspection revealed nothing unusual. Both magnets are still in the prop drive.

5. The spark plug sparks each time the prop is rotated slowly or rapidly.

6. Engine compression is excellent.

7. At last resort I tried a starter but it had no effect. That was the first time a starter had touched this engine.

I would appreciate your help in solving this problem.
Thank you.
Old 09-26-2006, 11:14 AM
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Default RE: MVVS 26cc gas won't run anymore

It looks like the engine just runs off the prime and then stops. This could indicate a loss of carb pumping action. Check the connection between crankcase and carb. The heat may have caused this connection to leak.
While you are checking, also check the applied voltage to the ignition. (not the supplied voltage to the switch!)
How long has this engine been running? (hours)
Old 09-28-2006, 03:08 PM
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Default RE: MVVS 26cc gas won't run anymore

Hello Pe,
I've been applying your suggestions and continuing to troubleshoot the engine's refusal to start. I checked the connection between the crankcase and carb and it was OK. I tried to tightened the 2 nipples while I was doing that but they were not loose.

I checked the applied voltage at the ignition connector and it was 5.14 volts with a 500 MA load.

The engine has less that 2 gallons of gas through it. I don't know how many hours that equates to.

The picture below shows that the spring inside the spark plug cap is bent over (The spring was found to be bent the day the plug unscrewed and came out in flight). When I pressed on the spring it bent closer toward the side of the metal cap.

I straightened the spring but the engine still refused to start.

Frustrated and ready to retire this plane for the season I took it out to my back yard and gave it one more try. It did a few pops then after a long period of flipping with not even one pop, it suddenly sprang to life with no warning and ran just as well as it ever did.

I typed all of this just to say I'm still puzzled and never found out what the problem was. I suppose that this will close this forum string because the problem no longer exists. I just wonder if I'll be back here in the near future looking for help again.

All of your suggestions were valid trouble shooting steps and I thank you very much for your help.
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