Allis 7020 Cold Start Issue/Engine Health?
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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=210717
Printed Date: 13 Apr 2026 at 2:01am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: Allis 7020 Cold Start Issue/Engine Health?
Posted By: nowaktj
Subject: Allis 7020 Cold Start Issue/Engine Health?
Date Posted: 12 Apr 2026 at 8:02am
|
I could use some advice on my 7020. My issue is that it refuses to start cold
(tested in 50F shop). Background is that
this tractor has an engine transplanted out of M2 combine that I moved the
intercooler parts over from the 7020 engine. ·
The injection pump and injectors were rebuilt within
the last 90 days. ·
In swapping over the hardware from the original
engine, I did pull the cam to replace the front plate…and therefore I reset the
tappets. ·
The starter and batteries seem to spin the
engine fast enough. ·
In trying to start it cold, I tried it at ¼ throttle
and full throttle. Neither yielded success. ·
Using the glow plug for 60 seconds as a starting
aid does not help. The intake housing
does get warm during its’ use, so I think the glow plug is working. ·
If I plug it in and allow the block to get to
80F, it will start. ·
I measured compression with all injectors out
using cranking speed and a cold engine. The cylinders range 200 to 210 psi
across the 6 cylinders. o
This evenness leads me to believe I don’t have
one or two dead cylinders. ·
I measured compression after letting the tractor
get up to a running temperature of 140F.
I then pulled #6 injector, installed compression tester and then
restarted it running at idle (750-800 rpm).
This yielded a compression of 350 psi. o
This above test matches what I found in a 185
Service Manual…it states under similar circumstances, a healthy psi is 500. My 7020 Service Manual offers no criteria for
a compression test. I noted from the
parts book that the piston from a 185 to a 7020 is a different part number so I
don’t know if I can use the 185 spec. ·
When running, the engine has near zero blow by
out of the valve cover. This makes me
believe the engine isn’t shot. Also, I
can run it down the road in high gear and it seems to have plenty of
power. I wish I had access to a dyno to
measure actual horsepower. What are people’s thoughts on what my issue is? Has anyone ran a compression test on a healthy 649/301 turbocharged engine?
------------- D19D, D17D, WD, WC, Snobee, #83 Plow, SC Blade, 14' disk, 400 series planter, B , Terra Tiger, M Dozer w/Baker Blade, TL-12, 42S Grader, G |
Replies:
Posted By: Mikez
Date Posted: 12 Apr 2026 at 8:28am
| Who put injection pump in. Maybe not timed correctly. |
Posted By: nowaktj
Date Posted: 12 Apr 2026 at 8:34am
|
Forgot to add detail about timing. I have double checked and the lines match up perfectly for 18 degrees BTDC. The dampener mark could be off, so I moved the pump gear back 1 tooth and forward 1 tooth and it did not run as well. ------------- D19D, D17D, WD, WC, Snobee, #83 Plow, SC Blade, 14' disk, 400 series planter, B , Terra Tiger, M Dozer w/Baker Blade, TL-12, 42S Grader, G |
Posted By: DrAllis
Date Posted: 12 Apr 2026 at 1:46pm
| So, how did it start cold when in a 50 degree F shop before you had injectors and injection pump gone thru ???? Set your pump timing at 16 degrees BTDC and leave it there. Cranking compression with a known good compression tester should be over 300 PSI with all injectors removed. Running on one cylinder at 700 RPM should yield you 400 psi or a little better. So, you either have a real problem or you have a compression tester that isn't giving you correct numbers. What brand starter does it have?? A LUCAS ?? they are known for slow cranking speed, regardless of what you think of the cranking speed. I assume this engine has the DM-4 style injection pump?? and that would have 15 to 1 compression pistons. LEAVE THROTTLE AT A DEAD IDLE TO START. |
Posted By: injpumpEd
Date Posted: 12 Apr 2026 at 2:30pm
|
200 psi is not enough to start a cold diesel engine. I always do compression tests with starter, not per Ac procedure of it running on the other 5 cylinders. You problem starting is at cranking speed, so that is the speed you need to check it as you did, and it proved to be a problem. Faster cranking speed will definitely raise the cranking compression pressure. I don't feel you have an engine problem as much as you have a slow cranking problem. Looks like a great application for an ether start and a gear reduction starter lol! ------------- 210 "too hot to farm" puller, part of the "insane pumpkin posse". Owner of Guenther Heritage Diesel, specializing in fuel injection systems on heritage era tractors. stock rebuilds to all out pullers! |