Plow truck won't start. Cranks but doesn't fire. Spark checker shows intermittent and weak spark, haven't checked fuel pressure or compression, but pretty sure they're OK. Fuel relay just got a new pigtail last year and new pump and filter so it should be good. It ran OK for a while after the fuel problem was fixed. Now I think I have something else...

Took ICM off and took to Auto parts store, they checked it and said it's good. Put it back on distributor. Put new cap and rotor on distributor.

Checked the oil and there seems to be some fuel in there, might be due to me trying to start it a lot in the past couple weeks.

Any ideas where to start? I have some basic mechanical skills but if anyone can narrow it down I would appreciate it. I don't know where to start.