• Steel Soldiers now has a few new forums, read more about it at: New Munitions Forums!

  • Microsoft MSN, Live, Hotmail, Outlook email users may not be receiving emails. We are working to resolve this issue. Please add support@steelsoldiers.com to your trusted contacts.

M931A2 compressor does not pump?

ichudov

Member
399
15
18
Location
Chicagoland, IL
I have an M931A2 semi tractor. It starts and drives (used to).

However, today, it started fine but would not build pressure. There was air in the tanks. Maybe 80 PSI. The pressure was below 90 PSI but it would not start pumping. I purposely bled all air out down to 10 PSI, and it still would not build.

Then I disconnected the line from the pressure governor going to the top of the compressor, and still it would not pump air.

What could cause it. I looked at a few 9-2320-272-24-* Tms and did not find much about that. Thanks
 

doghead

4 Star General /Moderator
Staff member
Super Moderator
Steel Soldiers Supporter
26,246
1,179
113
Location
NY
So, this didn't help?

COMPRESSED AIR SUPPLY

No air pressure (warning buzzer sounding, air pressure not building to

normal operating range as indicated by gauges) . . . . . . . . . . . . . . . . . . . . . . .

Air pressure does not build to normal operating pressure

(above 80 psi (552 kPa)) according to gauges. . .. . . . . . . . . . . . . . . . . . .


Each has a section for diagnosis.

Did you follow them both, and made no progress?
 
Last edited:

Suprman

Well-known member
Supporting Vendor
6,861
696
113
Location
Stratford/Connecticut
I recently had to rebuild the unloader in one of my trucks. It would build air slowly if you revved it a little. There is an O-ring that had dried out. The rebuild kit is available from Fleetpride it was around 50 bucks. I had to take the compressor off to do it so if you head that route make sure you have the front and rear gaskets. They can be ordered from any Cummins dealer I had a few around I never order just one gasket.
Will
 

ichudov

Member
399
15
18
Location
Chicagoland, IL
Doghead, thanks. I was looking in the wrong TM. Sorry. I found the right one searching for your quote.

I did start following the procedure. I disconnected the governor line. Then I felt the output air line. It was not exactly hot, but it was warm, on a cool day.

I simply followed the "warm" line by hand. It led me under the truck to a big pneumatic component under the truck, in front of the middle axle. And there, I think, I found the problem: All the air was coming out of the bottom of that component. (note that I photographed it from underneath, so the bottom is the nipple in the middle of it).

Photo of it is attached.

I am going to do some digging and find out what that component is and why it is malfunctioning.
 

Attachments

doghead

4 Star General /Moderator
Staff member
Super Moderator
Steel Soldiers Supporter
26,246
1,179
113
Location
NY
You may be able to visually identify that component by looking at TM 9-2320-272-24P-1.
 

doghead

4 Star General /Moderator
Staff member
Super Moderator
Steel Soldiers Supporter
26,246
1,179
113
Location
NY
Looks like...
 

Attachments

Suprman

Well-known member
Supporting Vendor
6,861
696
113
Location
Stratford/Connecticut
If air is coming out of the center of your air dryer or big component as you call it, stick your finger in the hole and push up. Sometimes a little wd40 helps to get it moving again. A rebuild kit is available for that valve.
 

Triple C

New member
546
3
0
Location
NAPOLEON MO
A person doesn't play with a big truck very long before you get familiar with an air dryer. That by the way is where that air pop off sound comes from when your air gets built up. As Suprman said try some wd40 and I would take off the inlet and spray some in there then start the truck right away and see if that frees it up. Not an uncommon problem and not always a rebuild, sometimes they just stick now and again. Years ago when I drove over the road, one tractor I had drove me nuts with the air dryer, it was rebuilt several times but it just kept sticking. Finally got another one from a wrecked truck and no more problems. They get a personality for sure. Good luck.
 

doghead

4 Star General /Moderator
Staff member
Super Moderator
Steel Soldiers Supporter
26,246
1,179
113
Location
NY
The picture he posted does not look like the ctis air dryer to me(from looking at the TMs).
 

Attachments

Triple C

New member
546
3
0
Location
NAPOLEON MO
You are right doghead it doesn't but it looks just like the one I have on my truck.- BUT, I haven't spent any time under there to make sure that's what it is either!
 

juanprado

Well-known member
Steel Soldiers Supporter
5,614
2,923
113
Location
Metairie/La (N'awlins)
I would think so. All it requires is 24v for the heating element, mounting space, and plumbed in . The same model but 12v is used in the hd market.
 

ichudov

Member
399
15
18
Location
Chicagoland, IL
If air is coming out of the center of your air dryer or big component as you call it, stick your finger in the hole and push up. Sometimes a little wd40 helps to get it moving again. A rebuild kit is available for that valve.
Suprman, it was exactly as you said. I came to work today, pushed the valve up with a plastic stick, with a bit of effort it "clicked" and went up a little. Now the air pumps up. In fact, this Holset compressor is amazing in how much air it pumps and how quickly the tanks fill.

This, obviously, is not a complete solution and needs to be properly fixed.

I just bought a rebuild kit for this dryer. Haldex Midland DQ6026 Pure Air Plus Canister Filter Kit .

I think that this stuff is just regular maintenance stuff that needs to be attended to every so often.

Thanks a lot.
 

Suprman

Well-known member
Supporting Vendor
6,861
696
113
Location
Stratford/Connecticut
I dont believe that kit has the rebuild kit for the expello valve which is whats sticking on yours. It just has the cover piece over the valve. Spray wd40 up into it and see how it goes I think they definetly need some lubricant from time to time. Haldex DQ6020 is the expello valve kit for the ABS air dryer in my 939A2 trucks. It is good to replace the cannister it just unscrews and then you can pick up and out the brown tube piece. You can dump some air dryer alcohol in there with the cannisters out it cant hurt. If you do have to rebuild the expello valve you have to remove the air dryer to do it. I believe there are instructions in the DQ6020 kit.
 

ichudov

Member
399
15
18
Location
Chicagoland, IL
Suprman, do you think that I need to buy that kit DQ6020, or just spray/lubricate the existing expello valve and call it a victory?

If I was to lubricate it, should I just spray WD-40 from the bottom?
 

Suprman

Well-known member
Supporting Vendor
6,861
696
113
Location
Stratford/Connecticut
I would try to lube it. Not too much 2 small spurts then build air see if it opens and vents moisture at around 120psi. If you continue to have problems then do the rebuild.
 

F18hornetM

Active member
1,135
10
38
Location
Ocean City, Md
Just bought a M931 and it has the same leak at the air dryer as well. The truck is in great shape, almost looks like its been in storage. Think I'll just try some air tool oil in the inlet and see if it will unstick. If that doesn't work will take apart and clean. Let us know how you make out with yours.
 
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website like our supporting vendors. Their ads help keep Steel Soldiers going. Please consider disabling your ad blockers for the site. Thanks!

I've Disabled AdBlock
No Thanks