Hello all. Scratching my head on this one. I have a 1986 Mack Superliner triaxle that will not build air unless the system is pumped down to nearly empty. It builds to 125psi as it should. The compressor has less than 30k. The unloader valve is clean and I have replaced the governor twice. It also has a brand new air dryer. The lines appear to be clear and yet this keeps happening. Any thoughts are appreciated.
Mack will only build air when pumped down to nearly 5psi
Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by bust7015, Sep 16, 2021.
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Faulty governors or plugged signal line to governor seems like the most logical. I’d disconnect the signal line and see if compressor starts pumping. If it doesn’t it must be governor or it’s adjustment.
beastr123 Thanks this. -
I did just find something out… I was away while the truck went out for a new frame. Turns out the builder replaced some airlines between the tanks. Maybe he hooked up some lines incorrectly? Even so, the lines going to the governor are in the correct location. -
I thank the line to the control port should go to the wet tank. That line goes off the center port opposite the vent or exhaust port. Center ports go to the compressor and air dryer to unload.
spsauerland Thanks this.
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