Air pressure not building

Can you tell me exactly what part you replaced? We're having the same problem on our prostar. Took it to the dealer and it was working fine for them so they didn't do anything.

 

Probably about $20.00 . I always carried a spare in all my trucks. Never did change one on the road but gave one to a trucker from Alabama that couldn't build up pressure at the top of Kicking Horse Pass near Golden British Columbia. I recall that it was a holiday and everything was closed. he was a very happy campere that bought me breakfast at the Husky in Golden. I also installed it for him as he never had any tools.

 

Hmm did you check the air dryer my freightliner the spitter on the bottom would stick open and not build any air... D0 you build an air? Both needles on the air gauge down or just one?

 

I have the same problem with my Cascadia. Pressure only builds up to 60 on both tanks but it stays there while idling and doesn’t build up anymore unless driving down the highways

 

If it build higher pressure with higher engine speed, I would say you have a massive leak somewhere.

 

Having low air pressure problems builds only to 65 to 70 lbs. New compressor, new regulator, no air leaks.

 

Have you checked the intake line(s) and strainer if it has one?

 

I have a 2016 cummins ISX only building air at idle. replaced the air dryer assembly including governor and still have the same problem. it only builds to about 85 psi but will hold no leaks anywhere. took the line off compressor and its seems to be pumping properly at idle and 1500 rms

 

I would check the inlet line making sure it’s not kinked, collapsing at the higher RPM’s or obstructed with crud. If it has a strainer check it. Then I would check the unloader valve. Then I would check the discharge line from the compressor for carbon crud. If found replace it.