air compressor

change the governor.

 

Dito on the governor valve.

 

Park Unplug the air from the trailer then turn off the engine & look for air leaks (watch your air gauge) NO leaks on the truck?
Hook the Air to the Truck&trailer Keep the truck brakes on and release the trailer (Watch The Air Gauge) for Air Leak...No Leaks?
start looking at replacing the air governor (Cheap) ....Still have problems ? It's you air compressor going coo coo for cocoa puffs.

 

my guess is you have a leak on the airline between the Governor and air dryer

 

red or blue air line to trailer has a leak.

 

Governor, Of course some air dryers will cause that condition when the silicate in the filter becomes saturated. kinda like a warning system to let you know its time to change the filter.
Wanna have some fun? I once took an old whoopee cushion from my childhood, cut it up and inserted it on the relief valve of my air dryer, sure got a lot of comments about it at the truck stops!

 

Compressors fine. It's doing what it's suppose to. Check the line from governor to dryer like ezrider said or possibly the governor.

 

I guess no one noticed that he said the gauges never move. If it were a leak, the gauges would bleed down and you could see the cycle. I'm guessing that since he said it was at highway speed, he's hearing the air dryer blow off repeatedly. When the air dryer filter is saturated it creates a back pressure which fools thhe governor into thinking its time to stop the compressor. Once the back pressure slacks off the compressor kicks on again in a continuous
cycle. Of course I dunno know nuthin about Cumapart engines, All my trucks always had Kittypillars.
View attachment 63970

 

Apparently 2 of us did notice he said that and that's why we told him to check the pressure line from governor to dryer. When that line leaks off pressure it tells the governor psi is low and will cause constant cycling of dryer. That's on any engine brand