Rear Air Tank Pressure Alarm

[dennis45]

Found one of my earlier posts on this subject. Here is part of the text from that post with the Cummins info.


Cummins Service bulletin 012-013 and 012-003, Air Compressor Carbon Buildup is a procedure to remove carbon buildup from the cylinder head and unloader by injecting ATF into the top of the compressor using a Cummins Kit P/N 2892280.

Just found one source for the kit and it is a pricey little devil.

https://www.ryderfleetproducts.com/c...-p-340-2892280

[Sky_Boss]

Originally Posted by dennis45

Found one of my earlier posts on this subject. Here is part of the text from that post with the Cummins info.


Cummins Service bulletin 012-013 and 012-003, Air Compressor Carbon Buildup is a procedure to remove carbon buildup from the cylinder head and unloader by injecting ATF into the top of the compressor using a Cummins Kit P/N 2892280.

Here is the procedure https://quickserve.cummins.com/qs3/p...12-003-tr.html

[dennis45]

Originally Posted by Sky_Boss

Here is the procedure https://quickserve.cummins.com/qs3/p...12-003-tr.html

That's the one. My bill from the truck shop was just over 1K. Looking at this, I'd say it was a bargain.
The first option to replace the compressor was over 4K.
As I said earlier, my air system has never worked this good since I acquired the coach.

[Sky_Boss]

Dennis,

I tried to followed your suggestion. My problem is that I'm not on level ground so it wasn't prudent to release the park brake and fan it until it popped.

I first started by firing up the motor and putting it in high idle I increased the idle from 1000 to 1200 rpm. As I have seen so far the rear bags inflated more quickly than the front. The rear time was pretty near normal as I can recall but the front bags took several minutes to get what I think was fully inflated. During that time the front gauge was 140 psi and the rear held at about 75 psi.

After the front bags looked fully up I kept the idle up to 1200 rpm and eventually the gauge went to 140 psi and the governor popped.

I then decided to do the test again. I dump my air bags and then fanned my brakes until the rear gauge was as close to ZERO as I could get it. The front gauge stayed at 140 PSI. I then started the engine and set idle at 1200 rpm.

Elapsed time (MIN:SEC):
3:21 - 65 PSI, alarm off, rear bags started to inflate.
4:00 - front bags started to inflate, rear bags appear fully inflated.
5:30 - front bags appear fully inflated
6:00 - rear gauge at about 140 psi and the governor popped.

It took about 10 moderate pumps of the peddle to reduce rear gauge from 140 PSI to 65/alarm. That seemed normal. I didn't count pumps to get to zero.

I'm feeling more confident that the coach is drivable to a shop instead of having a mobile tech come out. I'm leaning to issues related to the compressor and/or the SB you brought up.

I did get out and spray down the places I could reach up front but didn't see any leaks. I couldn't easily get to the rear level valves or connections in the rear.

The only other test I was considering was inflating the bags and sitting on them for a few hours and watching the pressure. However, the rear pressure has always shown a slow leak when sitting so that might not have told me anything new. It doesn't normally leak below about 90 psi unless I dump the bags. When I dump the bags it goes down to about 70 psi but after a long period might get down to the 60ish range. After a long stay it is 50/50 that I will get a low pressure alarm that cleared out quickly.

Time will tell and I'm getting smarter. LOL

[dennis45]

To clarify,

When it's working correctly, it should Unload at 120 - 125 and as the air pressure drops the governor should cut in around 110 - 115 and compress to cut off again at 120 - 125.
My problem was that it would not start to load until I reduced the pressure to below about 75. The reason was that the unloader would stick until the pressure differential across the unloader was low enough for it to switch.

Good Luck,

[Sky_Boss]

Originally Posted by dennis45

To clarify,

When it's working correctly, it should Unload at 120 - 125 and as the air pressure drops the governor should cut in around 110 - 115 and compress to cut off again at 120 - 125.
My problem was that it would not start to load until I reduced the pressure to below about 75. The reason was that the unloader would stick until the pressure differential across the unloader was low enough for it to switch.

Good Luck,

Good info. My cutoff was adjusted up to 140 psi. I don't see my issue being related to the cut in PSI. Unless we do find a leak the output of the compressor is looking like the problem.

I have to admit that I don't understand why my front tank pressure gauge doesn't budge. That just doesn't compute for me yet. LOL

[twinboat]

Originally Posted by Sky_Boss

Good info.

I have to admit that I don't understand why my front tank pressure gauge doesn't budge. That just doesn't compute for me yet. LOL

Its electric, tap it with your finger. It may be stuck.

[dennis45]

Have you found the instrument test function that Spartan uses. It will cycle through the range of the gauges which will confirm if it's a gauge issue or input to the gauge. On mine this function is acessed by holding the button below the odometer. Guessing yours should be similar.

[Sky_Boss]

Well...problem found.

The tech found a hole in the discharge line caused by rubbing against a frame/rail. With overnight shipping of the part from Spartan to Fountain, CO it looks like it will be about $900. The part should be in the shop by early morning (Thursday) and installed by the afternoon.

[dennis45]

Originally Posted by Sky_Boss

Well...problem found.

The tech found a hole in the discharge line caused by rubbing against a frame/rail. With overnight shipping of the part from Spartan to Fountain, CO it looks like it will be about $900. The part should be in the shop by early morning (Thursday) and installed by the afternoon.

Good deal. Thanks for the update.

[JC2]

Originally Posted by Sky_Boss

Well...problem found.

The tech found a hole in the discharge line caused by rubbing against a frame/rail. With overnight shipping of the part from Spartan to Fountain, CO it looks like it will be about $900. The part should be in the shop by early morning (Thursday) and installed by the afternoon.

Exactly what part did Spartan send that justified a charge of $900?

[OldHatt45]

Was it by any chance Spartan Part # 0639-MM5-004

[Sky_Boss]

Originally Posted by OldHatt45

Was it by any chance Spartan Part # 0639-MM5-004

I haven't seen the part number but the tech told me it was a long hose from the rear up to the tanks up front.

The $900 estimate included up to $150 overnight shipping and labor to install. Sure is a lot better than a new compressor. LOL

[Sky_Boss]

Originally Posted by OldHatt45

Was it by any chance Spartan Part # 0639-MM5-004

YEP...that was it. I saw where the leak developed. I was told the new part was a bit longer than the original to help give it some slack to help avoid rubbing.