Thanks for the post!

Can you confirm the model number of the unit? I'm familiar with the "M109CL300-22", so that "G" you have in the model# may be incorrect.

Either way, your model is probably identical to the unit on the web page below:

www.mastertoolrepair.com/portable-oil-ba...09c300-p-748802.html

Most likely the motor is the reason why this is happening. You could be losing amp draw when the unit reaches 100 PSI, as the motor works harder the higher PSI you have in the tank.

I would honestly get an electrician to test the motor and capacitors at this point.

Or, you can contact a technical rep with Coleman Sanborn directly at 888-895-4549.

- MTR

A little more to add to my previous post...

If the unit will build 100 PSI it sounds like the pump is probably OK but I would check to make sure the pump turns easily and that the motor runs unloaded as it should. Take the belt off and turn the pump by hand and run the motor with the belt off for a good duration to heat it up.
If both the motor and pump seem to be OK unloaded then I would suspect that maybe the check valve could be bad. If the check valve tests good then the motor should be electrically tested.

You can find out how to test your check valve by clicking on the below link:

www.mastertoolrepair.com/how-to-test-check-valve-p-22524.html

- MTR