HELP: 7.3L IDI won't rotate 360 deg.

[BDCarrillo]

I'm on board with the pull heads and eval, but you oughta be able to narrow down a valve issue (if that's the case) by pulling the glowplugs and all of the rocker arms. Then shoot 20-30 psi of air in each glowplug hole. Any air rushing out the intake or exhaust will identify which valve may be goofed up. If you do find one, I'd start with pulling that head to see if a rebuild is even worth your time.

Rotating the motor backward and cranking the starter so that it "slams" was a horrible idea...

 

[madpogue]

I would start by pulling the VALVE COVERS and turning the engine again, just to see what each pushrod, rocker, etc. is doing. That might provide a clue as to whether you have stuck valve.

 

[Camo_Kidd]

Pulled the head with the engine still in relatively painlessly. What I found was the front cylinder (the one with the pulled plug when I bought it) was stuck at TDC and wouldn't budge when the engine rotated. At least I picked the correct head to pull...... Now its time to pull the pan and find the broken connecting rod or cap.

 

[cpdenton]

Ahh. Well there you go. Hopefully that rod didn't open up anything in the block that isn't supposed to be open.

Report back and let us know what you find. Btw, the oil pan is nearly impossible to get completely off without pulling the engine. The oil pump pickup has to be off for the pan to clear the crossmember.

I have never tried it personally, so let us know what you find out.

 

[icanfixall]

Stop right there and pull the engine. Its really a horrible job trying to remove the oil pan with the engine in the frame. Drain the oil. now stick a screwdriver up in the drain hole. Feel it hit something.. Thats the oil pump pickup head. It hangs down that low in the pan sump. Usually you have to remove the motor mounts and the fan shroud. then jack up the engine enough to slip the pan free of the engine over the cross member. No matter what.. your removing this engine to repair or probably replace it. Now seeing you have told us there is no water in the oil then there is the slight chance the damage did not crack open a cylinder and allow water in the oil. When you drain the oil you will know for sure if water is in the oil. water being heavier than oil so it will be the first thing to drain out of the oil pan. Thanks for letting us know what you found.

 

[riotwarrior]

Hmmmmm....

 

[jaluhn83]

Pull the motor. If the crank moves and piston doesn't you've got a piston or rod that isn't in one piece anymore....

There's no real way I can think of where that would happen without causing significant damage to the cylinder - ie you'll need block machine work. Beats me how it didn't punch a whole at least into the water jacket, but even if it didn't there's been pieces of rod flailing around in there which would cause at least some damage, and I'd expect enough damage that you'll need a new block. May be able to sleeve the cylinder, though I'd be hesitant even if there's no visible damage due to the possibility of microscopic cracking.

I'm guessing the 'quit running' was much more violent than you were told, and someone has a very conveniently forgetful memory.... Though when mine pulled a wrist pin and punched the cylinder wall out (but not water jacket) I didn't hear a crash or feel anything, noticed it from the oil pressure going to 0 due to the crankcase now being full of coolant....

 

[OLDBULL8]

Me too. Hmmmmmmmm. Why all the History?