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the missing link · 07-20-2016, **(Subject: Air compresser )**

So first things first , I am not a mechanic , I can not spell worth a dam or type,and I am far from knowing much .
I have been having issues with my air system ( 871 isx ) .it started with my air dryer ,it would purge when the compresser would kick in then out and would air up ( only under high boost ). And eventually got worse so I did order one ,i know I had to replace it anyway , not a big deal , I just had a run of horrible luck and pushed further then I should of .
So it got worse before I got back to town (leaking air when the governor was out , so I said the hell with it and bypassed it . Worked like a hot dam for about a day and then get worse again in and out , losing air when the governer was out . Then it would not kick out so I figured I stop for the night and put a governer on in the morning .
Morning come and I put a governer on , I figured I had it fixed , fired up the truck , it went to 135 psi before it kicked out , I swear ,kicked the tires and started trouble shooting everything .
I hooked the dryer back up , switched lines , tested lines, I did everything. Meanwhile while this all is going on its kicking in and out all the time within 10 secs at times ( not losing any air presser in the tanks ).
So at my wits ends found the dirty word ( shop ) and limped it in . First rate guys I got to say .
So we went though everything again and again , changed governer again ,tried bypassing the dryer , everything .
So the only thing we can come up with is the compresser ( unloaded valve ). Which in cummins mind makes more since to have in the dam compresser unstead of outside on the top. Why would you change a 20 dollar valve when you can change a 1700 $ compresser .
By the way I just greased my truck / steering shaft before this , so my arms were full of grease , like I said very smart I am .....
Little bit more info with the dryer bypassed the compresser will not kick out
With the dryer hooked up it will relieve the extra presser
With shop air hooked up , the dryer will purge when the governer kicks out ,but the compresser keeps a ticking

So like I said the only thing we are smart enough to come up with is the unloaded valve is screwed . The lent me a van , I drove 1 hour to pick the compresser up tonight . Tomorrow I know if that's the problem .
It's been a long dam day
Any knowledge would be appreciated
With kept everybody updated
Thanks

dbl overdrive · 07-20-2016, **(Subject: Air compresser )**

There is a procedure for cleaning the UNLOADER valve and compressor using atf fluid on quickserve if its stuck.
Under compressor service. Also, I've used wd 40 to get it started and then atf fluid afterwards but I allways change out the filter after a couple days of running as it will blow chunks of soot from the compressor.

Waterloo · 07-20-2016, **(Subject: Air compresser )**

If the Quickserve fix with the ATF does not work, and you think you need a new compressor, STOP! Cummins has a head kit to rebuild the compressor! You do not need to replace the entire unit, as they rarely ever fail. And there is no need to remove the compressor to rebuild the head. The kit is roughly $400 - $500 and is not that difficult to replace. Instructions are on Quickserve.

the missing link · 07-21-2016, **(Subject: Air compresser )**

You live and learn , would be nice if was a little cheaper at times Sigh
But no one to blame but me .
I put the compressed on , it fixed to problem
Of course cummins dint have a rebuild kit available , I was tired as hell , tired of hitting my head against the wall . So I paid the price and got back on the road .
Like I said live and learn .
Hopefully this post will save someone else this headache or I am probably the only one this dense . Lol

Hammerhead · 07-21-2016, **(Subject: Air compresser )**

Glad to hear it fixed your problem.
And NO, you're not the only one...

Rawze · 07-21-2016, **(Subject: Air compresser )**

(07-21-2016 )the missing link Wrote: You live and learn , would be nice if was a little cheaper at times Sigh
But no one to blame but me .
I put the compressed on , it fixed to problem
Of course cummins dint have a rebuild kit available , I was tired as hell , tired of hitting my head against the wall . So I paid the price and got back on the road .
Like I said live and learn .
Hopefully this post will save someone else this headache or I am probably the only one this dense . Lol

When mine started showing signs of acting up, I replaced BOTH the air compressor and the whole air drier at the same time. --- I was not about to let it put me on the side of the road in the middle of nowhere. Sometimes you have to weigh the act of trying to save a bit of money against the possibility of getting towed from the middle of nowhere.