Reciprocating Air Compressor Troubleshooting, Motor Hang

[arieck]

I've got a 5hp air compressor that is doing something strange. There is a line running from the crankcase up to the top of one of the cylinders. I don't exactly know what exactly the line is for. I thought maybe it was some sort of top oiler, but there is no oil in the line and its not spitting any oil out when disconnected... just air. Anyway, if the line is connected the air compressor motor will hang upon a pressure switch restart. However, if i remove the line... the motor starts no problem. I know that unloaders and check valves can cause problems for motor starts, but I don't think that is an issue.

Does anyone know what this hose is for? Or why it would be acting this way? I can run it without the the hose, but its its harmful I don't want to do it.

 

[arieck]

I forgot to post pictures... might help. The line I'm talking about is the black one.

On, Motor Hangs

Off, Motor has no problem

 

[burgie]

Looks like a positive crankcase ventilation system...similar to an automotive system. I have one on my compressor (copper tube)...first pic in Post #23...

Is the tube clogged? Can you blow air through it?

http://www.garagejournal.com/forum/showthread.php?t=178791&page=2

 

[LG63]

Looks like an IR T30 and that is the crankcase vent tube that equalizes crankcase pressure with the inlet. Not sure why/how that would cause the problem you describe.

Have you checked for blockage of the inlet filter?

 

[arieck]

Thanks for the responses. The tube is clear and their is a strong pulse of air coming out of the bottom outlet, the top outlet has a push pull air flow that goes along with the cylinder. Maybe there is too much crankcase pressure and it is flowing it up into the top of the cylinder head where it gets trapped. Next thing I'm going to try is to individually cap these inlets and outlets and see what affect it has. Its still pumping air with the hose off (about 13 CFM), but its not where it should be (15+ cfm). This is a Toshiba air compressor, not really sold domestically (I got three of these off a printing company that had them incorporated into their big Toshiba assembly process). This is what they look like:

Pretty standard really. BTW Bergie, nice job on your restoration projects... man that's nice.