Hi Tobenna,

What exactly do you mean by 'will not start'? Does it do nothing at all when you try to start it? Or does it try to start, but can't get up to speed for some reason?

I assume we're talking here about a rotary screw type compressor, right?

If nothing happens at all, you're probably looking at an electrical problem. Maybe something's wrong with the temperature switch/sensor.

If it tries to start but it can't and it sounds like it is having a hard time turning around, it could be that there is pressure remaining in the compressor after shut down.

Every compressor needs to be started without any back pressure against the compressor element (in case of a rotary screw compressor), or the pistons (in case of a piston type air compressor). For this reason, there is a blow-off valve or unloader valve installed on the compressor.

When the compressor shuts down, this unload valve or blow-off valve releases the pressure inside the compressor. Now when the compressor starts up again, it has an easy start, because there is no back pressure.

Now when this blow-off valve malfunctions, pressure remains in the internal piping and the separator vessel . When you try to start the compressor again, is has to start against this back-pressure. It will have a hard time getting up to speed, and most compressors won't be able to start.

This could be the reason you need to wait two hours. After two hours, the pressure has escaped.

Maybe you have a completely different problem, but this is a common problem with air compressors. It's hard to say from here.

It could also be a true diesel engine problem. It is a strange problem though. The only thing I can think of is air in the fuel lines or something like that.

Please let me know how it works out or if you have any other questions or remarks.

Good luck

Hello, i have komatsu 550 kva generator. I did a servicing for the gen and  i started it twice and shut it down trying to it again it's very difficult to turn. Pls, what could be the problem. Thanks.