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Building air pressure slow

I'm trying to leave Clayton New Mexico. Turbos on. New exhaust manifold. Start it up to go and run engine runs good but for some reason the air pressure is building very slowly. Replace the haldex air system and the D2 Governor this past spring. It's taking 10 to 15 minutes to build up to a hundred 10 lb. What are my possible problems to look for? Do not hear any air leaking anywhere so it's not like a major hole somewhere.

Re: Building air pressure slow

Reply #1 –
Larry,

If you are not hearing a significant leak, then the air governor is the first place to look. Under $25 and easy to replace.

Sure it could  be something else but with no significant air leak, a reasonable place to start.

Re: Building air pressure slow

Reply #2 –
Is it possible for the filter or desiccant has plugged and slowed the air supply?

Larry

Re: Building air pressure slow

Reply #3 –
Loose belt? Have you checked your engine air filter? Tap on the governor with a hammer.

Re: Building air pressure slow

Reply #4 –
That may draw air from the boosted area of the intake to the compressor .  Or the intake hose may be  connected in the wrong place.  Maybe a plug is still on the hose or something along that line. '
  Also a the relief valve mayb e leaking back into the air supply.
Look  closer  at the work that has just been done . 

Re: Building air pressure slow

Reply #5 –
Phred, belts aare good, air filter new and checked for good tight fit. And did percussive persuasion. 

Mike, the first thing I did was check that nothing was damaged from the other work. Can't hear any leaks. When I shut down the engine, the air pressure holds. It just takes forever to build up. After running the pressure up and down several times it seems to  build slightly faster, but not like it did coming in.

I was running 110 pds when I arrived but it was different when starting up today. Keep the suggestions coming.

Thanks, Larry

Re: Building air pressure slow

Reply #6 –
Check your book and trace the compressor inlet line. It wil be filtered and may or may not come from the pressure part of the air inlet.  It would build slower than in the past if it is connnected to the pre turbo area. 

Re: Building air pressure slow

Reply #7 –
Mr Wolfe10 is correct I would replace the air governor not much money easy to replace  I had one give me some problems last year I had a spare changed it out  built air good.

Re: Building air pressure slow

Reply #8 –
I had this issue twice. The first time my drier purge valve didnt close fully and was letting enough air out that it took a long time to fill. The second time my air line from the drier to the tank alongside the engine had a hole worn or melted thru it where it rubbed against the exhaust where it wasnt well secured. A new line made at the local hydraulic shop in five minutes and I was in business. Its tough finding leaks over the roar of the engine, but both times I found it by running my hands over the hose or spraying soapy water at fittings, lines, etc.

Re: Building air pressure slow

Reply #9 –
That was the first thing I checked was The Purge air valve. No leakage there. No leakage there. Started the coach up this morning it seemed to build air quicker but still not as good as it has in the past. Finally have the coach running where we can get out of Clayton.

Re: Building air pressure slow

Reply #10 –
Not sure if the M-11 has it but the Cummins manual for the 12 valve 8.3 suggests you clean/check a air tube coming off the air compressor for blockage(coked oil in the line),may be something to research.What about a worn air compressor?

Re: Building air pressure slow

Reply #11 –
Quote from: ohsonew –
. . . the air pressure is building very slowly. Replace the Haldex air system and the D2 Governor this past spring. It's taking 10 to 15 minutes to build up to a hundred 10 lb. What are my possible problems to look for? Do not hear any air leaking anywhere so it's not like a major hole somewhere.

In my world it doesn't matter if you replaced the D2 yesterday, for $25 I'd install my spare and be certain everything is all right with the D2.

That being said, when was the last time the air compressor's cylinder head was pulled and the unloader valve cleaned and the seal replaced?

And as John44 said always check the lines for obstructions.

Personal side note here:  On my Siata restoration project, after I replaced the brake master and wheel cylinders and purged the air from the rear brakes, I discovered the front flexible lines to be totally blocked.  So much for cutting a corner.  Four (4) new flex lines and I'm good to go.

Re: Building air pressure slow

Reply #13 –
I get the hammer part but what would a loose belt tell you about air pressure,air compressor is gear driven!!!

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Reply #14 –
Gear driven compressor, did not realize that, mine is belt drive

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Reply #15 –
Made it home from Pueblo and now have time to chase down the slow air build up. When I started, it still took about 20 minutes to build to 90# at fast idle. While driving, the pressure would build up to 115-120 and hold well. If I had to brake or use the retarder, the tank would drop down to between 90-100#. It would then build back up to 120 with ease, so I made the 600+ mile trip home. Decided to start with the easy stuff first. Pulled the dessicant canister and coalescent filter. The dessicant seemed very heavy, weighed in at just under 6#. The coalescent filter seemed oily with some oil &/or oil surrounding it. I have new filters coming on Monday. My question at this point is, how heavy should the canister be? When the new one arrives, I will weigh it to check, but was wondering if anyone knew off hand.

Also, I haven't checked, but where does the air compressor get it's air supply from? I would think that it is filtered somehow before getting to the compressor, but didn't know where the supply was from.

Thanks,
Larry

Re: Building air pressure slow

Reply #16 –
Hmmm, since it holds air ok once it builds up could the problem be at the 6-packs?  Did you look at the exhaust ports to see if they're exhausting air while the pressure is building up from first start-up?

Re: Building air pressure slow

Reply #17 –
Quote from: ohsonew –
Also, I haven't checked, but where does the air compressor get it's air supply from? I would think that it is filtered somehow before getting to the compressor, but didn't know where the supply was from.
Reference below says the air comes from the intake manifold.  Have to admit I haven't actually looked to find the source on my engine.

Air Compressors

Re: Building air pressure slow

Reply #18 –
Quote from: Chuck & Jeannie –
Reference below says the air comes from the intake manifold.  Have to admit I haven't actually looked to find the source on my engine.

Air Compressors


That is a common source of air for the air compressor.

The advantages:
Uses the main engine's air filter vs have to service two separate filters.
The air is already cleaned, compressed (by the turbo) and cooled by the CAC before it goes to the compressor.

Re: Building air pressure slow

Reply #19 –
Since it is serviced by the intake, is it possible that the cartridges filled up w/debris from the turbo? I haven't checked the six packs, but will when I get the new filters and restart the engine. Before I left Clayton, neither I nor the mechanic (younger man with good ears still) heard any leaks, at least not large enough to be audible. I'm certain that I have some small leaks through out which I will have to chase with soapy water, but nothing blatantly obvious.

Larry