Rear air suspension- Compressor works won't air up

[Gutless]

04 Rainier 5.3 with 250k. Bought at 170K and had to replace the rear bags because they would leak down over night.

Everything has been flawless for the last 80k miles until this weekend when i went to hook up a utility trailer to haul some furniture and it was really low, almost on the bumpstops.

Didn't think anything of it but it refused to air up. Checked the compressor by hitting the button to turn on the inflator and it worked like normal.

What causes the pump to turn on but not pump the bags up? The bags hold air great, but when loaded down it would not inflate.

I disconnected the level sensors from the control arms, set them to the "full bottom" position with the car running and it didn't air up.

I checked both level sensors on either side and they were intact connected to the control arms. I read online somewhere they are 75-100 ohm sensors and they both ohm at 89-90 ohms and do nothing when I move the arm. I assumed I had bad sensors.

I went to the salvage yard today and found 3 rainier/bravadas and ohm tested 3 sensors and they also ohmed at 89-91 ohms, no movement when I actuate the arm. I assume my sensors are OK and that ohm data I read is wrong and they operate on some other function.

I searched the forum and can't find anyone with the same issue. Any idea where to start?

I have bilstien air-spec rear shocks which are like a year old on the back and I really like the airbag setup so I'd prefer to get the system back alive.

Thoughts?

 

[TequilaWarrior]

There is a known flaw in the air compressor. It's been quite a while since I dealt with mine but if memory serves there's a valve at the top of the piston inside the compressor pump that has a tendency to corrode and fail. "Rebuild" kits are available but I usually can't find them. The simplest kit includes a small steel plate, a small spring, and a small rubber gasket. By the time I found out this information my pump was well beyond repairability. If your pump engages, but is not producing pressure sufficient to get the back end up - it's very possible this is your problem. You may want to talk to your salvage yard and see if you can get the air compressors from these vehicles with the assurance that you could "swap" them if bad. They may not charge much - they may charge through the nose. It depends on whether they know what they are worth. I ~might~ be interested in a working ECAS pump as I retrofitted by Bravada to simply inflate from the schrader valve in the hatch area by replacing the pump with a "T" fitting and removed the pump. My pump was 100% shot and a new replacement was around $700 at the time. If you choose to attempt to get these compressors pay very close attention while removing them from the donor vehicles (and removing yours). There are THREE air lines. I do not recall the number of electrical plugs but it may be 3 as well. There may be a video available to demonstrate removal/replacement of the pump.

 

[16vcabman]

If the pump is running but, the unit is not producing air then it is the pump. Did you verify that the Schrader valve in the car was actually producing air pressure? You can get a pump from Arrnott on Rock Auto for $565. You could pull it off a bone yard. My car I tried the dorman pump. Blew up the first Chuck hole I hit. Put old pump on and it worked. My car had a burnt wire and quit working before I bought it.

 

[northcreek]

The check valve that TW(above) refers to is the only serviceable part on your compressor. If that doesn't work, plan on a new compressor and there are two types, depending on your wheel base.

 

[Mooseman]

You should just replace the bag system with springs. Much cheaper and more reliable. Ride is not as plush but you won't have to wworry about it ever again.

 

[northcreek]

Curious to know what happened with this. Hopefully we will get a follow-up. Maybe he's taking Mooseman's advise and going the Fred Flintstone way...