portable air compressor bogs down

Hi Phil, Sorry for the late reply, I've been quite busy lately. Are you still having compressor problems? When you say "when switched from start to run", do you mean from completely stopped, to running unloaded, or do you mean from stationary (standby) unloaded, to loaded? I assume you mean that the compressor can start and run idle/unloaded (not really pumping compressed air), but it bogs down when putting the compressor in 'loaded' condition (starts pumping compressed air). If this is the case, it could mean two things: 1) The diesel engine can't deliver the power needed to run the compressor because there is something wrong with the engine. 2) There is something wrong with the compressor, and the diesel engine is not able to turn it around any more. I think it's probably number 1. If there was something (that serious) wrong with the compressor, you probably wouldn't be able to start the diesel engine in the first place. So, probably the diesel engine has enough power to turn the compressor in unloaded/idle mode, but not when it is put in loaded operation (it really has to compress air and work hard). Look for problems with your diesel engine. It could be as simple as a dirty, clogged-up fuel filter. It's hard to say exactly from the other side of the planet ;) Please let me know if it was helpful.