John Deere 420 cranks, won't start

[dustball8504]

Hi all, I have a John Deere 420 with the P220G Onan that quiit on me. About a week ago I had it running like normal. I pulled it out, changed the oil, cleaned the air filter and sharpened the blades. I ran it around for a little while and parked it. A few days later I went to mow with it and it won't start. It has spark at each plug and gas at the carb but will only backfire through the carb once in awhile. I tried starting it on gum cutter with no luck also. Any ideas??

 

[beenthere]

:welcome: to TBN

"gum cutter" not sure what that is or why one would use it for a starter fluid. Maybe others will chime in here.

 

[Toddao]

Gum cutter, I believe is a carb cleaner

Sent from my iPad using TractorByNet

 

[Kish318420]

Hour many hours on it? Try a tiny amount of gas down the carb. If it fires, time too deep clean the carb. If not compression test and then a leak down test. What color was the spark? Was this with just the wire or the plugs?

 

[dustball8504]

Hour many hours on it? Try a tiny amount of gas down the carb. If it fires, time too deep clean the carb. If not compression test and then a leak down test. What color was the spark? Was this with just the wire or the plugs?

Spark was blue/white and it was with the wires. Tractor has 930 hours on it. Motor was rebuilt at 800.

 

[JerryK]

Wonder how good of a spark you have... I know the crank sensor [ electron thing that fires the coil ] goes bad on those, but mine failed completely. Probably due to age, vibration, and heat cycles. Mine would run like a top for about 4 minutes, then die...

 

[Kish318420]

Have you pulled the plugs and checked them? They could be badly fouled or even be just bad.

 

[dustball8504]

Have you pulled the plugs and checked them? They could be badly fouled or even be just bad.

I forgot to add that the plugs was the first thing I tried. The ones in it are new. I'll compression test it this evening when I get off work and report back.

 

[Richard001]

Hi all, I have a John Deere 420 with the P220G Onan that quiit on me. It has spark at each plug and gas at the carb but will only backfire through the carb once in awhile. Any ideas??

Typically backfire on cranking indicates bad spark timing or bad cam timing.

Is it possible that the flywheel nut came loose causing a bad timing situation?

Richard

 

[Kish318420]

Well you got air, fuel, spark. The last thing needed is compression. It is time to dig deeper. Compression check both cylinders (doing both a dry and wet (drop oil into the cylinders via spark plug). What is compression readings for the cylinders? Leak down test for possible valve problems (valve seats, valves, valve stem seals, valve springs or bad cam).

When rebuilt - What was done? Was the bore measured? or just honed and new rings? Was the electronic ignition module replaced along with the plastic flywheel magnet that goes on crank ( if it is black plastic nope, there were know to fail, new ones are grey plastic, tip from boomers_influence@yahoo.com)