Cant turn down air pressure

[racing4funn]

its builds to nearly 150 psi and a blow off valve opens and repeats every 40 seconds or so.


I thought this was the adjustment high up on the firewall under the hood


But I have given it 5 complete turns counter clock and nothing changes.

 

[doghead]

You have a bad PPV.

 

[Suprman]

Yup been covered a whole bunch of times

 

[chadande]

You can just remove it and install an elbow in its place to see if it is the issue. It is on the front of the wet tank which is in front of the air dryer (see pic). Mine was bad when I picked up my truck.

 

[racing4funn]

PPV huh? ok easy enough but is there somewhere on this site that I can find a part number and where can I order one? Guess I will start on ebay.

 

[porkysplace]

PPV huh? ok easy enough but is there somewhere on this site that I can find a part number and where can I order one? Guess I will start on ebay.

google search on this site works great ; Pressure Protective Valve "PPV"

 

[racing4funn]

I took mine apart and cleaned it real good. The piston moved freely but that didnt fix my problem. I read somewhere that I could replace it with a elbow to verify that it is the problem. True? If so then I can remove the internal guts to it and install to see if that works?

What is it doing anyway? So with just an elbow my tanks are going to start regulating to 120 psi or less?

 

[Suprman]

It opens at around 65 psi. Air for horn wipers and the governor is fed by its opening. If you have a failure in one of these secondary items and air is leaking the ppv will close at around 60psi to protect braking ability. If it did not close and you had a large air leak once pressure went below 50 or so psi the brakes would engage and the truck would stop.

 

[racing4funn]

My wipers and horn works as early as 30 psi. So my PPV is not working correctly and is passing air at will. I got one on order

BUT that is not affecting the over pressure problem. Why is it climbing to 140 psi+ and continuously blowing the blow off valve.

Where is the sensor to stop the compressor?
Thanks!

 

[M35A2-AZ]

I think the reg. in your 2nd pic is the cutoff for the compressor. I would move it all the way in and try it or replace it.

 

[racing4funn]

I think the reg. in your 2nd pic is the cutoff for the compressor. I would move it all the way in and try it or replace it.

I thought I read somewhere that counter clock wise (out) turned it down (less pressure). Anyone verify?

 

[doghead]

I know I have seen the answer to your latest question in the TMs, in the -20 or -24(whichever applies to your truck series) troubleshooting section.

Asking this on a forum is bound to get varied answers, so at best you have a 50/50 shot at getting the correct info.

If you know what adjustment you made, just reverse the adjustment back to where it was. It is not your problem.

We've told you what your problem is. The same diagnosis could have been made by following the troubleshooting section of the TM or searching the site.

 

[doghead]

Did you read the link in post #4? And the link in that link?

http://www.steelsoldiers.com/showth...valve-opening-on-M925-Frozen-air-lines-valves

 

[racing4funn]

Yea Ive spent hours on the TMs but being new to them Im very inefficient and with a 15 month old boy to watch I run out of time.

I played with it and it is clock wise to lower pressure. I got it set on 128 psi and I wouldnt dare ask but rather I will look up what pressure it is suppose to be.

Thanks for pointing me in the right direction.

 

[M35A2-AZ]

I think you do turn it in for down.

 

[doghead]

Did you ever get this issue resolved(and how)? Others may be able to learn from this thread if you update it.

 

[max1008]

The tm steps work perfectly. We thought the ppv was bad on a friends truck. followed the tm and it ended up tracing it back to a broken flare fitting. I beleive the first step in the tm is to test the gauge to make sure it is reading properly.

 

[Warthog]

Another "I got to have it NOW" thread. "Don't bother me with all the details...JUST TELL ME HOW TO FIX IT!!!!" No time to post a followup.

 

[Jakelc15]

Here's my attempt to help this dead end thread.

The air governor on the firewall regulates when the compressor goes on and off. Cut in and cut out pressures. If you pressure is over 150 and the protection valve opens to bleed off air then your governor is bad. The governor is the only thing that tells the compressor to stop making air.
The ppv valve, as was explained earlier, separates the 2 air tanks. Tank 1 operates brakes, tank 2 has your accessories plumbed into it. At around 60 psi the valve should close, protecting the brake side from a leaking accessory. Any air from the compressor only goes into tank 1, until 60 psi is reached and the valve opens.
A faulty ppv will not make your pressure exceed the governor setting.

The governor is adjusted by removing the plastic dust cover on the end and tightening or loosening the nut. I think it takes a 1/2". In for more pressure. If the governor needs to be adjusted more than 5 - 10 psi it is probably bad and needs replacement. Most of the time when they go bad they stick in one position, usually all the way open or closed. If you start your truck and it barely builds any air, tap on the governor, it will usually start working again and you can drive your truck into the shop.
If you have to adjust it from 150 down to 130 where belongs, the governor is probably bad and in a week or two it will be regulating itself down to 110.

I hope this helps someone. I hate reading 50 pages of thread on a topic that has no resolution at the end. It better at least have pictures!

 

[racing4funn]

Did you ever get this issue resolved(and how)? Others may be able to learn from this thread if you update it.

Yes did you read post #14. Please read before attacking.

Excellent post on #19. If there is much to be learned from this post its #19. Some people are very helpful. Well everyone is is helpful that are trying to be productive. Thanks