I have an old IR compressor in the shop right now. It came here because it has an air cooled Deutz F3L912 that isn't starting right. It cranks a long time and smokes black but it won't quite catch. It seems that it is staring under load. We have checked out the engine, of course did all the easy stuff air supply, fuel supply, compression. We did replace fuel filters, and some fuel lines that needed it anyways. The injectors were poor on a pop test so sent them out as well. Checked and adjusted injection pump timing by spill test. We did figure out that it does start if we open a little air valve back beside the compressor. Finally we separated the compressor from the engine, the engine is starting good without the compressor attached. I don't have much experience with the compressor side and we are stuck with repairing this unit now. Does anyone have experience on what goes wrong with unloader valves/ compressors to cause this?
Your diagnosis that it's starting under load makes perfect sense. I'm not sure how the IR compressors are set up, but on smaller (8 or 10 gallon) gas powered wheel barrow air compressors, the only way to start the machine is to flip the unloader switch, otherwise it starts under load. Is it possible this is a new owner that doesn't know the starting sequence? Did you try searching the nameplate info to see if there's an operator's manual for it? Another area to look on compressors is a stuck check valve somewhere on the discharge of the compressor between the compressor and tank (sometimes screwed right into the tank inlet fitting). If the check valve sits for a while, sometimes the check valve sticks/rusts shut and creates so much backpressure the compressor won't start or run. This is more typical on small electric compressors though.
A screw compressor like this has an unloader valve that blocks the compressor intake. We took the valve all apart and found worn components, waiting on parts again. I wish that I had an air schematic for this thing, I can’t quite wrap my mind around how this valve works.
Are the engine glow plugs working, Does the fuel rack go into full fuel at cranking speed. If the viscosity of the oil in the screw is too thick, no go on start up. Hopefully the fuel spilling was done right, as few know how to find Deutz True Top Dead Center. I have a Deutz Degree wheel to ensure perfect timing. I know it starts with no load, but maybe the fuel racks cannot handle the load? Just a thought. Could be entirely a screw control problem as you are looking into. If valve is letting air through, that will translate into stalling of engine most likely. Think I have a book on these compressors. If I find will post a picture of air system. Simon C
An F3L912 doesn’t have glow plugs. I would need to check the intake heater to be sure but it really isn’t necessary for starting in the shop or at summer temperatures when this started acting up. The injection pump throttle lever is spring held to full throttle on starting on this unit. Now, I guess we didn’t actually check the actual fuel control in the pump but it does run correctly when it gets running. If it would never run right I would have sent the fuel pump to my injection shop already. I’m confident that the spill timing was done correctly, we are an everything Deutz shop. Of course we could still make a mistake but not because we haven’t done it before. Oil viscosity in the screw didn’t really grab my attention yet, it seemed like ATF like it should be but….
Checked my manuals , All Sullair for 185, 210, and 375. Sorry nothing on IR compressors anymore. Maybe someone else will chime in with a air schematic. Simon C
Don't know if this will answer all your questions, but it is better than nothing. No schematics though.
Hey thanks! This did help some.