I have an Air Venturi compressor. It seems to go to about 3800 psi and no higher, I think, Ran it for 45' and didn't see any increase in pressure above 3800. Maybe I should let it work longer or maybe there is something wrong with it.? With my luck I fear it will need some repair. I am going to have to do it. Is there a automobile TYPE repar manual for compressors? Is this common? Where to get parts if needed. Thank you