L245dt D1101A low compression

[Dmech]

My tractor has been hard starting and low on power since purchasing it (10 years). This problem is most probably due to low compression, around 250 psi on all three cylinders. No oil consumption but heavy blowby under load. There is no exessive pressure on coolant system or any other signs of bad head/headgasket

Repairs done during last 4 years:
-Glow plugs changed
-Injectors rebuilt with new nozzles
- Injection pump rebuilt with new plungers elements

During last winter I tore down the engine and found wear on the upper part of all cylinder liners and thought this would be the reason for the low compression. Due to this there was excessive pistonring end gap. The squish clearance was measured before taking the head of and it is in spec (0.7-0.9mm).

This was repaired by boring the cylinder liners oversized and installing new pistons and rings (+0.5mm). Block and head surfaces were checked to be straight and valves were lapped. New headgasket was thicker so now the squish clearance is around 1mm.

After the rebuild tractor has been ran for around 15 hours and the symptoms are still there. Compression on all cylinders is still around 250psi and there are about the same amount of blowby as previously. What could be causing low compression and can the blowby be caused by something else than worn cylinders?

 

[North Idaho Wolfman]

My tractor has been hard starting and low on power since purchasing it (10 years). This problem is most probably due to low compression, around 250 psi on all three cylinders. No oil consumption but heavy blowby under load. There is no exessive pressure on coolant system or any other signs of bad head/headgasket

Repairs done during last 4 years:
-Glow plugs changed
-Injectors rebuilt with new nozzles
- Injection pump rebuilt with new plungers elements

During last winter I tore down the engine and found wear on the upper part of all cylinder liners and thought this would be the reason for the low compression. Due to this there was excessive pistonring end gap. The squish clearance was measured before taking the head of and it is in spec (0.7-0.9mm).

This was repaired by boring the cylinder liners oversized and installing new pistons and rings (+0.5mm). Block and head surfaces were checked to be straight and valves were lapped. New headgasket was thicker so now the squish clearance is around 1mm.

After the rebuild tractor has been ran for around 15 hours and the symptoms are still there. Compression on all cylinders is still around 250psi and there are about the same amount of blowby as previously. What could be causing low compression and can the blowby be caused by something else than worn cylinders?

Blowby can only come from bad rings, piston size issue, or bad cylinder walls.

The compression numbers being low can be from thhe thicker head gasket.
I tell eveyone to go OEM on the head gasket no matter what else you use.
Have you confirmed you are using the right glow plugs and the right injectors?

 

[Dmech]

Blowby can only come from bad rings, piston size issue, or bad cylinder walls.

The compression numbers being low can be from thhe thicker head gasket.
I tell eveyone to go OEM on the head gasket no matter what else you use.
Have you confirmed you are using the right glow plugs and the right injectors?

Thanks for your reply!

During the rebuild the piston to cylinder linear clearance of the new piston was checked to be in spec with bore gauge. Also the pistonring endgaps were correct.

The combustion chamber volume should be 18cc when compression ratio is 21:1. 0.3mm thicker gasket causes an increase of 1.4cc in the volume, thus it should have very minimal effect on compression.

The injector nozzles and fire rings are with same dimensions as previously. I have to check if the glow plugs could be too short and cause the increase of the combustion volume. Seems unlikely but you newer know.

 

[whatsupdoc]

Glow plugs length is not going to change blowby. There has to be an issue
with the cylinders, pistons or rings.

 

[Russell King]

I don’t think this would cause all of the problems but it is easier to eliminate than other things!

That engine (probably) has a decompression mechanism. It is not supposed to be used to stop the engine but some people probably think it is the same as a “stop knob” that shuts off the fuel.

It does not shut off the fuel it opens up the valves and kills the compression.

I would start by being sure that the decompression mechanism is loose and the valves are all closing up properly.

Then there is a test called “leak down test” that finds out where the compression is leaking (valves, rings or ?). I can’t tell you how to perform that test (never have done it) but I imagine that you may already know how to perform it.

I would think that you eliminated valve problems by what you have done but I think this is an “easy” test to perform. Ask how to do it if you don’t know and I am sure someone else will be able to tell you what to do!