Does anyone know what the compression of a 1984 6.9L Diesel? I have read it was 22.5:1 and then another said 20.75:1. Also i was wondering if a diesel compression gauge will calculate this. One of those you place in the glow plug and test it.

Where can one get one of these diesel compression gauges and how much money is it?

 

I have seen them on Ebay for $50-150. I think someone here purchased a guage at NAPA for $135. I am going to check NAPA myself today. I need to get one.
Bob

 

Does the guage give you numbers or does it just have a green space and the compression is ok when it is in the green space; bad in the red space?

 

I am pretty sure it is numbers.
Here are some I looked at.
Bob

http://cgi.ebay.com/ebaymotors/Diese...spagenameZWDVW

http://cgi.ebay.com/ebaymotors/ws/eB...7669685&rd=1,1

 

I always figured that when I got around to buying one of these units I'd just pick up a cheapy from HF:
http://www.harborfreight.com/cpi/cta...emnumber=93644

Comments? Looks similar to the 1st ebay posting, substantially cheaper than the Rotunda...

Mike

 

I think I will go to Harbor freight this week and get that one. Good find! It doesn't have to last forever.
Bob

 

Thanks for the info guys

 

Went to Harbor Freight today and got a diesel one for 39 bucks, I did a compression check on the #2 cylinder. I dont know if I did it right or not but I cranked like 20 seconds and it read around 450psi. Is that good or bad? I really dont know the typical compression of a diesel.

 

400-500 PSI is good. But 20 seconds is much to long, and will put a strain on the your starter.

Your only supposed to crank it for 3 compression cycles, long enough so that the engine hits the compression stroke on the cylinder your testing 3 times. So you will see the needle go up 3 times. If you do more then that, you may be skewing the results.

 

I just did some research on how long to crank it. I dug out my 6.9 and 7.3 manual and it says 8 times to get the proper reading. The manual that came with the compression checker said to 6 times. You say 3 times....What should I go by?

Is between 400 and 500 typical?

 

I would go by the gauge manual, so 6 times.
Just remember to do it the exact same way for all cylinders.

400 to 500 is good.
Lowest cylinder should also be within 10% of the highest cylinder.

So if the highest is 450, 450*.10 = 45, 450 - 45 = 405, the lowest should be over 405.

6.9 should be 22.5 to 1.
7.3 should be 21.5 to 1.

 

2 cents worth .... the harbor freight and EBAY units are most probably going to be identical and while they are not badly made , they are very difficult to use on most of cylinders of the IDI...I could use it only 3 cylinders without pulling injector lines. The usable adapter is straight in and it needs to be angled instead... you could buy the the kit and a better adapter is available elsewhere!