Bigboy down again,M923 won't build air past 59psi

[The HUlk]

Have you ruled out the horn air solenoid valve by disconnecting the wires to see if it stops blowing? A spring causes it to stop blowing the horn which may be wore out or stuck.

I don't know where that connection is in the wiring you asked about. I would guess it's on the engine side of the firewall because the PCB and Horn Fuse are both located there. However a short to the horn wire you highlighted should not cause the horn to blow because the highlighted wires are both always energized when the ignition switch is on.

 

[tbar123]

I just went out and disconnected wire 26 from the new horn solenoid( not used stock) and the horn did not blow. The original problem is still there with or with out the transfer case engaged.So should I replace the shift lock solenoid or cylinder next?

 

[The HUlk]

Okay, now we know the horn solenoid is not the problem. Wire 26 is not the problem either, it should always have 24V on it. Somewhere wire 25 is being grounded is what is causing the horn to blow. Wire 25 could be making contact against the body anywhere between the horn solenoid and the horn switch.

 

[tbar123]

I was able before the rain came in today to replace the shift lock solenoid and cylinder. I also replaced the damaged transfer case shifter electronic components.The parking brake wires have been disconnected ( because I don't have the replacement part yet) . So with the horn still disconnected I started bigboy back up and there is no change to his status. The air is still escaping into the intake stack. I did shift the transfer into low and back a few times and that didn't change anything. Any other suggestions? Thanks for any and all advice!

 

[Andyrv6av8r]

I was able before the rain came in today to replace the shift lock solenoid and cylinder. I also replaced the damaged transfer case shifter electronic components.The parking brake wires have been disconnected ( because I don't have the replacement part yet) . So with the horn still disconnected I started bigboy back up and there is no change to his status. The air is still escaping into the intake stack. I did shift the transfer into low and back a few times and that didn't change anything. Any other suggestions? Thanks for any and all advice!

Have you tried applying shop air without the truck running? If so, was the air still escaping into the intake stack?

 

[tbar123]

I have not. I tried once before in one of the glad hand places and couldn't get the ttruck to air up. Is there a better way to go about it?

 

[Andyrv6av8r]

I have not. I tried once before in one of the glad hand places and couldn't get the ttruck to air up. Is there a better way to go about it?

Did you use the red one' front or rear, and open the valve? No reason why this shouldn't work.

 

[tbar123]

I know it was a front one and I know I opened the valve. I think it was the red hand.

 

[MtnSnow]

The Emergency air is on the Drivers side Front and the passenger side Rear.

 

[tbar123]

I hooked up shop air today and the air is escaping into the intake stack. I then removed the air line from the cylinder on the rear drivers side just in front of the parking brake drum. The air stopped leaking into the intake. SO I followed that line down and took all 3 lines off from the item in the picture. I then tracked that line down which goes to the front axle engagement switch on the dash. On another note the other line leads to the air horns.

 

[marchplumber]

AWESOME!!! Serious detective work there!! Thanks for sharing, keep us informed. =)

 

[swbradley1]

That's funny, it looks like the same place they take air for the Frankentruck air ride seats.

(Yeah Ben, I know you don't think it's funny now...)

 

[tbar123]

Ok, I have no idea what to think now. I started bigboy yesterday just to make sure that the problem was still there, and of course it was. I came home today and helped Yolner load his stuff and then took the dash switch for the front axle out. I thought that I would take the exit line off and there would be the problem. Nope! So I put the switch back in and tracked all the lines down again and couldn't figure it out. So I said what the heck,I'll start the truck and see what happens. NO AIR LEAKING!!!!!! Ok this is good,but WTF. So I flipped the switch for the front axle and after about 5-8 seconds the leak started,Shut it off and no leak. Switch right! But why would it leak only with the front axle engaged? Not at the switch?
So after reading what another person had wrote, I checked the temp on the air compressor. The head was 154.8 Just 8" below where the cummins stamp is was 78. I also noticed that the air was a lot slower building after I introduced shop air.
I just hope I can go for drive tomorrow!

 

[tbar123]

Well went out today and started the red camo, then started big paperweight and of course the air intake leak was present again. I made 2 video's of the problem,mainly because I was holding the phone shutoff button and didn't recognize it. Any help would be appreciated!
https://www.youtube.com/watch?v=6xx463Svo2Q&feature=youtu.be
https://www.youtube.com/watch?v=i7d4yoK_mvQ&feature=youtu.be

 

[BenRoberts]

I didnt go through all the previous post so sorry if this is a repeat but could the spring brake rubber be leaking causing it to go back through the intake?

 

[tbar123]

I found the problem( Major thanks to a fella named Marc,not sure if he has an account here or not.)With his guidance we went through what could be the problem. He suggested that I take the lines off this valve and blow shop air through them to see if this was it. Bingo! I blew air through the line in the rear of this valve and sure enough air was bleeding into the stack. So I took the valve out to see if I could rebuild it.Nope of course not. But I got it working good enough to reinstall to double check the problem. Problem fixed.But the air horn problem is still present. I think when the transfer case lever shorted out it burnt the horn solenoid!

 

[Andyrv6av8r]

If I were you, I would bypass and disable that valve anyway. You can manually engage the front end with the switch on the dash.

 

[tbar123]

So after replacing the above valve, I thought everything was good to go, NOPE! I flipped the dash switch and there was the air in the stack again. So I called Marcfeld up and he pointed me in the right direction again with a few tests to do. I aired the truck up with shop air and when I flipped the dash switch I could hear a dull ping sound coming from the transfer case.So I had my sister (Thanks Hope) flip the switch while I was under the truck. It was coming from the "front axle engagement air cylinder". So I took it out and it looked brand new on the inside. After further investigating, The seal on the piston looked to be in wrong. So I flipped the piston over and reinstalled it. Problem fixed! It appears somebody installed the piston backwards which allowed the air to slide past the seal causing the problem. Here are a few pictures of the cylinder. First pic correct, second pic wrong!

 

[Swamp Donkey]

So after replacing the above valve, I thought everything was good to go, NOPE! I flipped the dash switch and there was the air in the stack again. So I called Marcfeld up and he pointed me in the right direction again with a few tests to do. I aired the truck up with shop air and when I flipped the dash switch I could hear a dull ping sound coming from the transfer case.So I had my sister (Thanks Hope) flip the switch while I was under the truck. It was coming from the "front axle engagement air cylinder". So I took it out and it looked brand new on the inside. After further investigating, The seal on the piston looked to be in wrong. So I flipped the piston over and reinstalled it. Problem fixed! It appears somebody installed the piston backwards which allowed the air to slide past the seal causing the problem. Here are a few pictures of the cylinder.View attachment 630046View attachment 630047 First pic correct, second pic wrong!

That makes about 3 or 4 examples that have been posted of them being installed backwards now. Mine doesn't leak but I think I'll open her up anyways to see. Glad you got it fixed.

 

[marchplumber]

So glad she's not a paper weight anymore!! Really glad ya got your truck back! Glad there were people out there that could help also!! ENJOY!!