Compression Tester
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=167373
Printed Date: 06 Aug 2025 at 5:13am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: Compression Tester
Posted By: PDehring
Subject: Compression Tester
Date Posted: 13 Jan 2020 at 2:47pm
|
I was looking to buy a compression test kit/tester but would like to have one that works well on the 301 & 426 engines. I know it needs to have a higher pressure rating (1000psi) for diesels but that's about it. I've never messed with one but I understand the concept of what is being done. Anyone have a recommendation or a make/model that works well for these engines?
------------- 1937 M Crawler, 1963 D21, 1964 D21, 1965 D12 SIII, 1970 220, 1976 185 |
Replies:
Posted By: DougG
Date Posted: 13 Jan 2020 at 3:31pm
| Pretty sure - if on an Allis your good at 500 psi and less on a compression tester, seems I'm wrong- sorry! |
Posted By: Joe(TX)
Date Posted: 13 Jan 2020 at 3:43pm
|
A diesel compression tester needs to be 1000 psi. You will also need the adapter for the type of injectors you have. ------------- 1970 190XT, 1973 200, 1962 D-19 Diesel, 1979 7010, 1957 WD45, 1950 WD, 1961 D17, Speed Patrol, D14, All crop 66 big bin, 180 diesel, 1970 170 diesel, FP80 forklift. Gleaner A |
Posted By: DrAllis
Date Posted: 13 Jan 2020 at 6:54pm
| 600 psi is enough on any A-C diesel engine. When you use the starter to check any 426, you'll be less than 400 psi. Your adapter thru the injector hole will be the same for 301 and 426 EXCEPT for those 301's and 4-cylinder turbo engines that have a copper injector sleeve in the cylinder head. |
Posted By: PDehring
Date Posted: 14 Jan 2020 at 7:13am
|
Is the adapter for a 301 & 426 a 'standard adapter' that would come in a kit or is it something more exotic? ------------- 1937 M Crawler, 1963 D21, 1964 D21, 1965 D12 SIII, 1970 220, 1976 185 |
Posted By: DrAllis
Date Posted: 14 Jan 2020 at 7:34am
| I made my own, so I can't tell you on that. I would think it could be very similar to some IH or JD engines injectors, but like I say, I don't know for sure. |
Posted By: ACinSC
Date Posted: 14 Jan 2020 at 8:57am
| Just checked my 40 year old Penske comp gauge out of curiosity . It goes to 300 . Never checked a diesel . Interesting post . Thanks |
Posted By: SteveM C/IL
Date Posted: 14 Jan 2020 at 9:11pm
| Book proceedure for DDA was install tester and run engine. Don't remember speed. was time consuming for all 8. |
Posted By: Lonn
Date Posted: 15 Jan 2020 at 7:07am
If I remember right, you warm up the engine first then test at idle speed running while checking for each cylinder. Called a running compression check. I think we did this in school way back when. If so I know I never did it again but I'd think a running compression check would be more accurate than a cold cranking test (book would specify at what speed the engine had to be cranked at for that too IIRC) but maybe the repair manual would specify the correct pressure for one or the other...........................................Or I could be all wet and remembering things I never did at all.  ------------- -- --- .... .- -- -- .- -.. / .-- .- ... / .- / -- ..- .-. -.. . .-. .. -. --. / -.-. .... .. .-.. -.. / .-. .- .--. .. ... - Wink I am a Russian Bot |
Posted By: DrAllis
Date Posted: 15 Jan 2020 at 7:39am
| Running is how AC wanted it done too, but if you are diagnosing a hard starting engine, a cranking compression test is better. AC provided no specs for this, so I compiled my own data. You'll find 350 to 375 psi with the starter is pretty normal for a used engine. |
Posted By: SteveM C/IL
Date Posted: 15 Jan 2020 at 7:37pm
| LOL Lonn...I remember a lot of stuff that never happened |