Hello all. Thank you in advance for any insight you can provide here.

This is a friends dozer and it won't start. Here is the history I know of it as told by him: It ran fine. It sat for a couple years and he went out to move it from hither to yon and it started and drove onto the trailer. Got to yon and went to unload it and the main engine wouldn't start. They dragged it off the trailer and it has sat for quite a few years. He goes to work on it and still cant get it started. He talks to a guy in the area that is supposed to know these engines and he told him that since it has a coolant leak, that is what is causing the low compression.

I immediately said no way, but he insists that is the problem. I just can't see how that can be, but what do I know? I'm a John Deere mechanic.

So that is my big question to begin with. Can a leaking water pump and radiator cause low compression?

So far we have gotten the starter motor running and main engine turning but joy in Mudville. I have bled the fuel system including on the back side of the pumps. I removed the line from #4 and pointed it back while cranking and it shot fuel about six inches. I then took my wrench and held it on the tip of the line and was able to stop the flow.

I have been searching and a couple of things I need to check are if the fuel rack is moving with input from the fuel lever and is fuel coming out the tell-tale hose. I pulled the hour meter and checked #2 & #3 cam lobes on the IP and there is no indication that they look worn down from it being low on oil, though I may be missing something.

I know that the compression release is working because Valve lash comes and goes when moving the lever.

We will fill the pump oil again and I'll do those checks. If you could let me know about the coolant/compression thing, I would certainly appreciate it.

Check the compression release again and make sure the valves are fully closing. You will probably have to pull the rocker cover to do that. Some exhaust valves could just be stuck open from sitting. Do you get a reduction of RPM when the compression is turned "On"?

I’ll say no, a coolant leak should have nothing to do with low compression.

I think you’ll find the rack is stuck in shutoff. lots of those old tractors have enough slack and misalignment in the throttle linkage that it takes a good snatch on the throttle to move the governor. You should be getting a thick cloud of mosquito choking white diesel “smoke” while cranking it with the fuel on. Note that it’s usually best to warm them up with the fuel off and compression ON and occasionally open the throttle to see if it wants to start hitting (puffs of black smoke). If it doesn’t start firing, close throttle and continue warming. Note the decompression control is flipped to RUN for full compression and Start for easier turning with the intake valves held open slightly. The decompression mechanism has no effect on the exhaust valves, just intakes.

If you take the side cover off the injection pump housing you can see whether the rack will move fore and aft or is locked. If it’s stuck and the problem is NOT the governor, it’s likely one of the fuel pump plungers is stuck up and it’s lifter return spring isn’t strong enough to pull it back down to follow the injection pump camshaft profile. This will be obvious as you roll the engine over you’ll see that one or more lifters doesn’t return to the cam base circle position. The plungers can be sprayed with penetrating fluid and gently pried or tapped back down but generally should not be twisted as the gear quadrant is only clamped to the plunger When they are manufactured to calibrate the fuel delivery rate.

If the lifters are all moving up and down but the rack is not free to move back and forth with minimal pressure, I would move on to diagnosing the governor. but the first part of that is to give the throttle lever a good strong tug to the rear toward the seat. It wouldn’t be the first one that just needed a good snatch.

Low compression from sitting along time can be valves not seating and sealing good or stuck valves, broken piston rings or even injector valves stuck open and blowing compression back through the nozzle.

"Norm wrote:

Check the compression release again and make sure the valves are fully closing. You will probably have to pull the rocker cover to do that. Some exhaust valves could just be stuck open from sitting. Do you get a reduction of RPM when the compression is turned "On"?

Yes, we get a reduction in cranking speed when comp release is moved to start. I also pulled the rocker cover and while cranking, I could feel all of the valves go from no clearance to clearance when moving the comp release. I didn't measure clearance, but my fingers tell me that they are all similarly loose.

"Rome wrote:

Low compression from sitting along time can be valves not seating and sealing good or stuck valves, broken piston rings or even injector valves stuck open and blowing compression back through the nozzle.

I'm going over this in my head and thinking of how to check all of these. I don't think that its the valves leaking or stuck open or compression release because when cranking with the Comp release off, I can hold my hand over the intake and it's a solid suck with nothing blowing back.

Broken piston ring problems could maybe be checked by checking blowby.

Nozzles sticking blowing back. Could that be checked by pulling the side cover off the IP and looking for pressure coming down from the pumps? It would have to get past the pumps as well though so I'm not sure. I would think that if it's blowing past the pumps, the pumps are shot. So does this sound right: Fuel bypassing the pump would be shot pump. Compression bypassing the pump would be injectors and pumps?

Does this sound right at all?

"ccjersey" wrote:

I’ll say no, a coolant leak should have nothing to do with low compression.

I think you’ll find the rack is stuck in shutoff. lots of those old tractors have enough slack and misalignment in the throttle linkage that it takes a good snatch on the throttle to move the governor. You should be getting a thick cloud of mosquito choking white diesel “smoke” while cranking it with the fuel on. Note that it’s usually best to warm them up with the fuel off and compression ON and occasionally open the throttle to see if it wants to start hitting (puffs of black smoke). If it doesn’t start firing, close throttle and continue warming. Note the decompression control is flipped to RUN for full compression and Start for easier turning with the intake valves held open slightly. The decompression mechanism has no effect on the exhaust valves, just intakes.

If you take the side cover off the injection pump housing you can see whether the rack will move fore and aft or is locked. If it’s stuck and the problem is NOT the governor, it’s likely one of the fuel pump plungers is stuck up and it’s lifter return spring isn’t strong enough to pull it back down to follow the injection pump camshaft profile. This will be obvious as you roll the engine over you’ll see that one or more lifters doesn’t return to the cam base circle position. The plungers can be sprayed with penetrating fluid and gently pried or tapped back down but generally should not be twisted as the gear quadrant is only clamped to the plunger When they are manufactured to calibrate the fuel delivery rate.

If the lifters are all moving up and down but the rack is not free to move back and forth with minimal pressure, I would move on to diagnosing the governor. but the first part of that is to give the throttle lever a good strong tug to the rear toward the seat. It wouldn’t be the first one that just needed a good snatch.

Awesome. I have gotten some good ideas, but I think the first thing that I need to do is pull the cover off of the IP and check the rack and plungers.

I agree with you on the coolant/compression thing but he is convinced that coolant leak = low compression. But, I don't know what he told the guy who told him that or what that guy heard or what my buddy heard, but it's hard to convince people when their mind is made up. But the coolant leaks need to be addressed regardless, so maybe it's best just to go that route.

I'd still like to get it running first. Maybe even get it out of where it is so I don't have an audience.

You can check the injection nozzles by removing the fuel line at the pump and see if there is air blowing back through the line while turning engine over on compression.

The 5J has a cover on the back of the IJ pump that covers the throttle connection. (5U doesn't have this housing.) It's a dry--no oil housing. With the cover off, you can see the outer end of the fuel rack and see exactly what it's doing. Also, the gasket on this housing tends to dry out. Then condensation rusts the inside parts, or dust gets in and gums up the works. Clean it out with solvent while you're in there, oil the end of the fuel rack, and put in a new gasket as soon as it becomes convenient.

If the "expert" was referring to a compression leak inside, like the head gasket, you would have coolant in the oil pan. After that length of time it is very unlikely that it would turn over anyway, but if someone forced it, there may be a plethora of busted wreckage inside the engine. It doesn't sound like that is the case.