Hello all,
Im sure a lot of you have seen my posts about the valve stem seal job that I did. These are the results of my compression tests:

I was happy with the results until I got to cylinder #5.

2- 378 PSI 1- 378 PSI
4- 365 PSI 3- 360 PSI
6- 365 PSI 5- 320 PSI
8- 370 PSI 7- 360 PSI

I think this is how the cylinders should be numbered (correct me if I'm wrong) if you are looking at it from the drivers seat, therefore I think it is my #5 that is low. I put some oil down in the cylinder and checked again and the compression shot right up to 380.

I was hoping that as many of you as possible would post your compression test results as well as what your truck does with those numbers. Things such as smoke, oil consumption, does it have a miss, etc.

I am trying to rule things out and find out if the compression is what is causing my problems or injectors or something else.
Thanks in advance!

 

Are you sure all your fittings on the gauge had a good seal? Was this a cold engine?

I had one compression tool give me about 360-380 when cold, then I used a better gauge set with a good seal to get 400-420 when cold (310K miles).

The oil in the cylinder with a jump in compression does not bode well, I'll grant you that.

I have another engine that I bought with 180K miles, and this cylinder is indicative of what I saw on the other 7 (dead cold) with the OTC compression checker.

 

2,4,6,8 are on the drivers side. 2 at the front of the truck by the radiator.

 

I got the harbor freight gauge and bought a separate check valve so not using the quick connect check valve that comes with the kit. I feel confident that my gauge is good and all of the seals as well. The engine was cold but I don't think it being warm would have changed it more than maybe 10 psi per cylinder. So granted my compression is probably a little better than what I have listed above. I had them numbered as if you are sitting in the driver's seat so it is correct then. Thanks!

 

I fought the seal on my Horrible Fright compression gauge, and it gave me different numbers every time I tested the engine. A repeat with a better gauge set gave me much better and more consistent numbers. I'm not saying buy a better gauge (yet), I'm suggesting that maybe a repeat of the test will yield different results.

 

I have the same one. I replaced the gauge (was 1000psi) to one that is 600psi. The thing does not reproduce consistent numbers.

 

You can see the OTC gauge in my video (OTC 5021), here is the fitting (OTC 6076) that goes in the glowplug hole:




Because the OTC adapter for the 7.3L has an O-ring, I just spin it in had tight and it never leaks. The compression test is very fast with this tool - and very reliable. The later stuff looks better than the one in the picture. I looked into the price of the OTC 5020 universal diesel compression test kit... yeesh.

 

The rubber hose with the snap-on kit would be better. A lot less work.

 

I tried one of those and threading was a bugger for me. The OTC was way easier - it goes straight in and clears the rocker arm.

 

Can this gauge be used to test running compression? Was wondering if that oring is actually rubber or some other material that can withstand the cylinder head temps.

 

rubber should be ok for 200f

 

Buna is good to 250, Viton is good to 400.

 

Whatever the material is, it's pretty tough - it's white. Are you talking running compression with the injector disabled?