Compression Test

[risgate]

Could anyone walk me through how to do a compression test? I have a MF40 with the ad3 152 perkins diesel. I am getting no reading whatsoever when I do it, but I am not sure if i am doing it right. I removed the cap off of the injector, then removed the injector from the housing, attached the gauge, turned it over 6-8 times, and got no reading. The motor will not start (which is why i am doing the test), but shouldnt i get some type of reading?
Thanks in advance.

 

[Anonymous-0]

Is this on all cyls?

Try squirting a little oil in the test cyl. If your compression comes up, your rings are shot. Put an ear to the exhaust pipe. If you hear a rush of air when you should be in the compression stroke, you have a valve problem.

You could also pull the valve cover and see if any valves are stuck.

 

[Peter Richardson]

Good advise our farmer! I use an airline adaptor, its home made, has a short rubbered taper on the end and a quick release airline fitting on the other end, handle piece in the middle has to be enough to grip & push with hand. I pull an injector, push the short taper into the hole in the bottom of the injector recess and listen! If both valves on that cylinder are closed-I listen to the exhaust for escaping air, then the inlet, then remove the oil filler and listen there too. if alls well, the air pressure will push down the piston on that cylinder and you will hear no hissing there is a little hissing, even on a new engine. I find, on a worn engine, most air leaks past rings when the piston is at TDC. If one cylinder is much worse than the others, it needs fixing.

 

[mf40inme]

not jumping to conclusions, but it sounds to me like you may have a broken valve, or very worn rings. Although i would think even very worn rings would still register at least some movement on the gauge.

If it were a valve though, that might also indicate something slightly more serious, as the pistons on the perkins at TDC are flush with the top of the liners.

Were you on the tractor when it last ran, anything suspicious happen?

Might sound silly, but, are you sure your compression gauge is not frozen? Especially if all cylinders read zero.

good luck, keep us posted