Hello. I have a Sullair 125GPQ diesel air compressor that I am working on. I was told that the compressor is supposed to be working good, but that the rubber coupler between the engine and the compressor is shot. Once I got the engine running, the compressor would not build any pressure, so I suppose I should be looking at that coupling. My question is, how can you do a test on if the coupling is working or not? Thanks for the help.
If it doesn't have an inspection plate or shroud you can see the coupler through, the easiest check is that the compressor oil level at the sight glass doesn't move while running. It's not too hard to unbolt the cover/adapter and pull the compressor back an inch to get a look in there.
Got around to looking at the compressor today. Once it was running, the oil in the sight glass didn't move at all. I guess I will have to split the coupler housing from the engine block a bit and take a look at the coupler then. Is it also possible that such results could mean that there is a different failure within the compressor unit itself? Thanks
That coupler is the main failure point in my experience, and is a pretty easy/quick fix. You'd be dealing with a lot of noise, heat and metal in the compressor oil if there was an internal failure.