Troubleshooting a 620 Allis

[620Doc]

My Allis-Chalmers 620 has been periodically "pulling the engine down" when I have been mowing. I've tried turning off the mower clutch, taking the transmission out of gear, and putting the clutch in. I can turn the engine off for a few minutes and it will run fine for a few minutes. I have also changed the hydraulic fluid and filter. I use synthetic oil in the crankcase and the oil level is full. Any ideas what is wrong or other diagnostics I can perform to solve the problem?

[D-17_Dave]

First off pull the air shields off the side of the heads and check for clogged air flow. Then you'll go through the ussual fuel flow and ignition issues.

[620Doc]

Turns out to have been some bad fuel. It now runs fine after just running through.