Portable electirc air compressor not reaching beyond 120 PSI

[sprotz]

I have a 300 PSI 12V DC electric air compressor similar to this one:

https://images.app.goo.gl/MbjmzB3DxBmbnGdG9

 

I plug it in to a 12V DC, 3.5 Amps current and it inflates and stops at around 130 PSI. For a long time the needle doesn't go beyond that but I want it to reach 300 PSI. What could be the problem? What should I do?

 

Udate: I dismantled the thing and saw its simplistic construction. I saw that the piston and cylinder are short, and that the piston does not fully touch the end of the cylinder when pushed in. Also there is some significant amount of space between the piston, cylinder and the valve that prevents backflow. I'm thinking maybe the piston compresses air only to a certain point before receding and therefore not being able to pump in more pressure because of the space ? Because the compressor keeps pumping at full speed but the pressure gauge only ever reaches 140 PSI.

Edited August 28, 2020 by sprotz
update

[wingless]

Welcome to the forum.

 

FWIW, that compressor is a few notches above a toy, so the fact it is making useful pressure is good.

 

There are very few applications that require higher pressure, like 300 PSI. If those pressures are required, then this compressor might not be the best choice.

 

Yes, there must be volume above the piston. When creating a performance engine, one step that is used is to shave the head, to decrease the volume and to increase the compression. Another step is to replace the crankshaft to increase the stroke, increasing the displacement. Neither are applicable here.

 

My guess for the reason the pressure reaches a plateau is that the valves are likely incapable of greater pressure. There may be piston ring blowby causing this limit. There may be a leak causing the limit.