I just recently purchased a 1993 F-350 Crew Cab that has a 7.3L IDI International-Navistar diesel with the stock turbo and 5 speed manual. The truck was apparently running then quit and sat for 2 years before being sold to me. I went threw the normal steps to try to get it running. 2 new batteries, new starter, fresh fuel. The problem is when you turn the key there is a big CHUNK. I thought it might be hydro-locked so I disconnected the IP and pulled all the glow plugs and same thing. When I put a breaker bar on the crank I can rotate it backwards like 7/8 of a turn before it halts again. Try cranking it and it just slams into the same spot (I can tell because I marked the spot with some soap stone). I have also tried shooting some PB Blaster down the plug holes to try freeing up any rust. I don't know if a valve is stuck or something like an injector broke and fell down in there but something is deff. keeping this engine from turning a full 1/8th rotation. Could a bad IP do that? What's everyones opinion on this???
HELP: 7.3L IDI won't rotate 360 deg.
- Thread starter Camo_Kidd
- Start date
this is not an opinion. this is a pretty damn good educated guess.
you have valve issues, or some kind of deposits developed on the top of the pistons.
the heads must be pulled.
IMO a headgasket failed, before the 2 year sit.
you have valve issues, or some kind of deposits developed on the top of the pistons.
the heads must be pulled.
IMO a headgasket failed, before the 2 year sit.
Not necessarily. It could be blowing coolant into the combustion chamber.
However, all you said was it was running and then quit. Without knowing the circumstances under which it quit leaves a lot of things that could have gone wrong.
Any way you look at it, something is in a cylinder keeping it from topping out. Time to open it up and spend some money on parts.....
However, all you said was it was running and then quit. Without knowing the circumstances under which it quit leaves a lot of things that could have gone wrong.
Any way you look at it, something is in a cylinder keeping it from topping out. Time to open it up and spend some money on parts.....
most likely, i had a PSD do the same exact thing youre talking about.
i pulled the heads and there were rust deposits stopping the piston from going to TDC.
it could be a valve.
i pulled the heads and there were rust deposits stopping the piston from going to TDC.
it could be a valve.
I'm thinking pull the valve covers and see if the valves follow the rockers when you bar the engine over. One of the valves probably is broken or has a bent stem. There is very little space between the piston top and the valves when the valves are closed. If a valve hangs up it will contact the piston at TDC. Maybe a valve spring is broken.
I had someone watch it while I rotated the engine. Now the front most cylinder had a pulled glow plug when I bought the truck and on that particular cylinder neither rocker moved in the entire 7/8th rotation at all. Valve Springs looks good and I can't tell if the rods or valve stems are broken just by eyeballing them. I didn't pull the other valve cover yet because its under the relay and turbo, but I suspect its only 1 cylinder that's acting up since I can rotate the engine so much and I think I have found the one. I guess the next step is to pull the entire head.
icanfixall
Official GMM hand model
The heads must come off this engine to known whats wrong. Sad to say this but your engine and failed and someone may have told you less than the complete truth. no worries. Just remove the engine. Pull the heads and have a look see. Probably a dropped valve so do not try to crank past where it stops.you will just do more damage. As for the gap between the piston and the head.. Thats about 42 thousands.. Not much room for anything. The heads are flat. no combustion chambers like a small block chevy. Most engines have the pistons raise up out of the cylinders as much as 31 thousands at top dead center. so you see the only reason a piston does not hit the head is the thickness of the head gasket keeps the gap.
Might as well as start looking for a replacement engine...
As I was removing my original engine, I was turning the crank a 1/4 rotation at a time for access to the torque nuts and it froze right before I could get the last nut to rotate into position. It was stuck good. Ended up having to pull engine out with the torque converter hanging out... That was no fun...
I believe that I must have had either a piston with broken skirts that wore thru the wall or a bad head gasket. It sat for a month after I parked it before I started working on it. Had to be rust...
Thank God I had already found a good engine to stick in...
As I was removing my original engine, I was turning the crank a 1/4 rotation at a time for access to the torque nuts and it froze right before I could get the last nut to rotate into position. It was stuck good. Ended up having to pull engine out with the torque converter hanging out... That was no fun...
I believe that I must have had either a piston with broken skirts that wore thru the wall or a bad head gasket. It sat for a month after I parked it before I started working on it. Had to be rust...
Thank God I had already found a good engine to stick in...
bbjordan
Snow Monkey
jaluhn83
Full Access Member
Rockers not moving doesn't mean anything - likely both valves are on the low spot on the cam and the 7/8 turn you can get isn't enough to move either cam onto the lobe.
Pull the heads and check it out. Could be any number of things, likely will need major engine work but could be as simple as a bolt of something that got sucked in. Not that hard to pull heads, just label/take pictures so you can put it back when/if you need to.
Pull the heads and check it out. Could be any number of things, likely will need major engine work but could be as simple as a bolt of something that got sucked in. Not that hard to pull heads, just label/take pictures so you can put it back when/if you need to.
Thanks for the responses everyone. New to Oil Burners and IDI but pretty impressed so far! So my next question would be, since I know my trouble cylinder can I only pull just that head and replace that head gasket or should I do both anyway? And if anyone has a good procedure (or torque specs) on head/head gasket removal and installation I would appreciate it! I'll post what I find when I pull the head tomorrow.
jaluhn83
Full Access Member
Doubt you'll really be able to id the cylinder, and it's not much more work to just do both. I'd start with just one, 50/50 chance of finding the problem, and a decent chance that once you find that you'll wind up needing a new motor which means there woln't be a need to pull the other head. (well, in the truck at least - much easier once the motor is out)
The Haynes 'Diesel Engine Manual' has decent info. Mel (Ageam) wrote nice article long ago on it, but not sure if it's here or not - might check the FAQ section.
The Haynes 'Diesel Engine Manual' has decent info. Mel (Ageam) wrote nice article long ago on it, but not sure if it's here or not - might check the FAQ section.
depends on your budget, and your skill.
if youre comfortable around engines, and on a green back diet, i would pull both heads immediately.
see what you can see, and hopefully it rotate.
IF it still does not rotate, the block is done for.
if it does rotate, and you find an obvious issue, say a valve for instance, you may beable to hogepoge it back to life.
the issue may go deeper than you think tho, with trying to start it and it locked up, you could have a cracked piston/bent rod.
if you find rust in a cylinder, you can pretty much bank on your rings not sealing.
if you got a couple of grand to throw at it, i would look for another good running engine. and a new injection system.
had a really bad rod knock in my stock engine, i found a 94 7.3T for dirt cheap, and did a transplant.
but never ever ever, just do 1 head.
if youre comfortable around engines, and on a green back diet, i would pull both heads immediately.
see what you can see, and hopefully it rotate.
IF it still does not rotate, the block is done for.
if it does rotate, and you find an obvious issue, say a valve for instance, you may beable to hogepoge it back to life.
the issue may go deeper than you think tho, with trying to start it and it locked up, you could have a cracked piston/bent rod.
if you find rust in a cylinder, you can pretty much bank on your rings not sealing.
if you got a couple of grand to throw at it, i would look for another good running engine. and a new injection system.
had a really bad rod knock in my stock engine, i found a 94 7.3T for dirt cheap, and did a transplant.
but never ever ever, just do 1 head.
^^^^ This!
