Keith Browning Posted July 30, 2016 Share Posted July 30, 2016 I have not one but two New Jersey Natural Gas F750 trucks with Cummins engines that wont build air pressure. One will reach 60 PSI if I stand on the throttle and wait 3 minutes. The other wont build pressure at all. Anyone that has run across this please chime in. I am following the diagnostics in Cummins' EDS and I am supposed to connect a $725 compressor cleaner to the inlet port and "clean/flush" the cylinder head of the compressor. It essentially injects ATF to clean and free up the discharge valve from what I can determine. I doubt my company will invest $725 on such a tool to be used once. So the truck will now sit for a week until my manager returns from his vacation. I was thinking of squirting a little ATF into the compressor manually... And yes, there are no intake or delivery tube restrictions. One of the inspections is to measure the carbon buildup in the discharge tube. This one is perfectly clean so I am wondering if cleaning the head is going to have any effect. You know, this shit would almost be fun if it wasn't so unproductive. Quote Link to comment Share on other sites More sharing options...
JoeR Posted July 30, 2016 Share Posted July 30, 2016 Is your compressor inlet downstream from the EGR inlet? If so, you probably have some carbon cleaning to do. Maybe in the air tanks and brakes too. Check for a replacement intake manifold that has an inner pipe that allows the compressor to get air from upstream of the EGR. Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted July 30, 2016 Author Share Posted July 30, 2016 No. The air compressor intake is piped to the cold side CAC tube on a 2015 ISB engine. The inlet and discharge lines are perfectly clean. This is why I am skeptical of cleaning at this point but if it is a matter of sticking discharge valves doing so might free them up. Quote Link to comment Share on other sites More sharing options...
Buddy_M Posted July 30, 2016 Share Posted July 30, 2016 Certain of no air leaks? Even some smaller leaks have played hell with building reservoir pressure with me before on some of our trucks. Not sure what the ISB run for a compressor vs the ISX engines I see, but I have had to replace 2 compressors myself due to the same complaint. Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted July 30, 2016 Author Share Posted July 30, 2016 I have only looked at the first truck at this point and there are no leaks. If there are minor leaks that cannot be heard then I would think that those leaks would not cause the condition I am seeing. In the past I have seen air leaks cause continuous cycling of the compressor which is opposite from what I have here. On the ISB the compressor is mounted off the right rear with the Power Steering pump bolted onto the front of it. The steering works fne so I can eliminate a loose drive gear or other drive failure. Um, with the inlet hose off I can feel air going in AND out of the port which is why I believe the discharge valve is hanging up. Quote Link to comment Share on other sites More sharing options...
Buddy_M Posted August 1, 2016 Share Posted August 1, 2016 I dont see why you couldnt try squirting some ATF in the compressor intake. Another thing would be some seafoam spray, or any other type of engine intake cleaner that you likely already may have around that could decarbon the valves. Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted August 4, 2016 Author Share Posted August 4, 2016 Well I got to the bottom of it - looks like the discharge valve in the compressor head is stuck. Got it out and took it apart and found rust packed in the bore. Apparently these two trucks were built without air dryers and no automatic water ejectors on the tanks. Should have one or the other and with the manual drain valves there is no guarantee the tanks are being purged with regularity at all. So for now I ordered an overhaul kit for this Wabco single stage compressor which comes with a new head, gaskets and head bolts. Then we will figure out what to do about the moisture control situation. This is a New Jersey Natural Gas vehicle. I know their trucks usually have dryers. The underside of this truck is packed with hoses and large pumps mounted to the inside of the frame and a PTO. I think it would have been much easier for the upfitter company to move the component than to attempt adding one after the fact. This is why I am going to provide an estimate to add moisture ejectors on the tanks. Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted August 8, 2016 Author Share Posted August 8, 2016 In case anyone needs to do this the head can be accessed and removed without removing the compressor or the fuel lines. Quote Link to comment Share on other sites More sharing options...
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