If your Comet Static 1700 is operating at lower pressure than it should, it might simply be one of the valves on the pump. See the below information on how to check the pressure check valves and hopefully fix your issue:
Here's the first one to check:
The first valve that needs to be checked is inside the outlet connection of the pump where the pressure hose attaches. Depending on how you have your machine setup, remove any fittings from the outlet on the pump. Look down inside with a flashlight if needed and you should see a plastic cover with a hole in the shape of a hex key. You can use an Allen wrench and remove that plastic piece to pull out the check valve. There should be a black plastic piece with some o-rings on it. Make sure those o-rings are there and look okay. If they are missing on damaged, that is likely the issue that is causing the machine to continue to run and run. Here’s a diagram for you:
“Sounds to me like the outlet check valve is not closing properly and its bypassing in the head while he pulls the trigger. This would explain no pressure and the fact that it won’t shut off with the pressure switch. I would suggest taking off the outlet hose and fitting and behind that fitting is the check valve that is probably stuck or damaged.
Check the spring (52) the valve (51) and the o-ring (50)
Sometimes the o-ring falls off some times the valve gets jammed and sometimes the spring gets broke or dislodged.”
To check the other valve, see below:
"I just performed this on my machine in my garage to try it out. I simply used a screw driver to push the pin via a hammer towards the inside of the case. Then pull everything out with some wider pliers to get a good grip on the white housing. I had to twist back and forth. Beware that there are a few very small parts in this assembly you may have to pull some out with needle nose pliers if it doesn't come out as one piece. Here is everything laid out: "
To recap, open up the third check valve and see if there is still a spring in it. Clean out the assembly and put back together as shown. Reinstall.