I got a 1990 7.3 f250 that hasn’t run in a while for next to nothing. I’m not too familiar with these engines. Charged up the batteries and load tested them, working perfect. When I try to crank it, the starter engages and you can see it try to crank but it can’t do it and just makes a violent clunk. I can spin the crank bolt by hand with a breaker bar until it stops I’m assuming due to compression. A friend said it might be the injection pump is jammed. Any ideas?
7.3 idi clunk but no crank
- Thread starter Dq400
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You should be able to continue to bar the engine through the compression. If you have a very solid sudden stop when barring it over, chances are there is a mechanical interference. Usually catastrophic.
Compression restriction is usually a squishy sort of bar over, whereas mechanical is a solid thud, and it won't move, period. Chances are it's not the injection pump.
Compression restriction is usually a squishy sort of bar over, whereas mechanical is a solid thud, and it won't move, period. Chances are it's not the injection pump.
IDIBRONCO
IDIBRONCO
I agree that it's probably not the injector pump. I kind of agree about the mechanical part. If your piston is already against the restriction, then you won't get a clunk from the engine because it can't move any farther. My guess is that the violent clunk noise is the starter trying to turn over the engine and the clunking noise is the starter teeth engaging the ring gear on the flywheel/flexplate. Normally, we can't hear that sound because as it's made, the engine also starts turning over.
Now that bad part, and hopefully this isn't it. There's a third type of restriction that I'm fearing here. That is called hydrolock. What happens all too often to our trucks is that water gets into a cylinder and stops that piston from moving any higher. Where this water normally comes from is two part. The seal that hoes in between the hood and the cowl is bad and water drips down onto the air cleaner when it rains and when snow melts. Then, if the sealing washer on the air cleaner isn't in good enough shape, water gets by it, down into the intake and from there, into a cylinder. My advice is to first stop trying to use that starter. That can bend a rod of there's hydrolock going on. Next, remove all of the glow plugs and use the breaker bar to turn the engine over by hand. This will force any water that may be in a cylinder out of the glow plug holes. After you can turn the engine over fairly well by hand, then use the starter to turn the engine over faster for a few revolutions to remove any remaining water. Then you can install the glow plugs and try the bar again. If you can turn the engine over fine, go ahead and start the engine to see what happens. If there's water in a cylinder (again, hopefully not), it can cause rust in that cylinder if it's been in there for too long.
IDIBRONCO
IDIBRONCO
You're welcome. Now you know to keep the air cleaner cover if it's raining. Even if it means throwing an old floor mat or something similar over it.
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