John Deere propane backfiring like crazy

[BlondeD]

.........my old...usually reliable.... propane tractor I use for spray rig duty has suddenly developed a bad backfiring issue, loss of power and just barely chugging along. And most of the old mechanics around here that know about propane setups have passed on. Anybody here with some hints.?????
Thanks

 

[hurleyjd]

Check the points in the distributor. The points may be about gone.

 

[Nesikep]

what he said, check the entire ignition system. bad plug wires and spark plugs too.. running it at night may help you see where something is arcing

 

[msplmtneer]

Also check the timing :tiphat:

 

[snoopdog]

Sounds exactly like the points .

 

[Texasmark]

Backfiring is the intake valve being open during the combustion stroke......Check compression, easiest and quickest way to determine if you have a valve problem. Could be bad seating surface due to carbon or sticking in the valve guide, not releasing when the tappet backs off it, broken valve spring, bent shaft, tappet out of adjustment.....too tight.

Or, with the LP, the regulator is loading too much gas into the intake to be consumed and prematurely ignites on the intake stroke....carbon on the piston glowing would support this theory.

Or timing too fast....ignition occurs before intake valve has closed...points pitted for that one.

All opinions, most based on prior experiences. I had a 196X year model 4020 LP......most temperamental tractor I ever owned and my first JD. Was glad when that sucker put it's knees under somebody elses table.