Dewalt Emglo 55168 motor starts to slow down as pressure builds to about 30 PSI. It really starts to labor. Any thoughts as to what could be causing the motor to strain and slow?

pressure switch fail

I just rebuilt my Emglo AM78 4CHV, new pressure switch, unloaded, check valve, aftercooler, and changed the #30 oil, It takes 4oz.
Runs like new after not cutting in/out correctly and purging air before reaching 125 psi. Kicked it down to 115 max psi via main spring setting. Don't need 125 for trim nailing and siding.
FYI don't use cheaper generic 125 psi pressure switch from Amazon!!
use Jenny M4-1247 (140-1074-01)

Its switched automatic on when the air-pressure in the tank comes to a lower level .
Other is by hand but there can be build on a circuit breaker on your type if the powercord was manual used by hand without pressure relief by switch.

the pressure sensor is likely defective. How old is it? take it to a Dewalt service centre

Worn ring and cylinder or bad valves maybe.

Hi
your pressure switch is bad. so it isnt cutting off the compressor. the part number is N003306SV and can be obtained from Dewalt on Servicenet.
Detail

Good luck and hope this helps

You need to install a pressure regulator in the line. That will allow you set the pressure.

Sounds like the pressure relief valve......It works as a relief so when the motor comes on it is not under a load/pressure. Much eiser to start not under a strain.........

the springs in the switch box may be misadjusted, one starts it the other shuts it down.check to see if one looks overly tight.also check the small hose going from tank to switchbox for clogs

hello,
well,you have to release the pressure,the cut out pressure at 120 psig.reached,and the cut in pressure maybe at 40 psig.so after realeasing pressure at cut in the compressor will run.if the compressor not run at cut in or after releasing check your power supply if still have,swicth off power breaker,by pass pressure switch,by disconnecting the line on terminals of pressure swtich,connect the line w/out pressure switch
the wire line should supply the the compressor,
open the service valve of compressor,switch on
observe if compressor run and develop pressure or air is coming out to nozzle,if that so switch off again and replace pressur switch.you have defective pressure switch,regards rate me,thanks