I have a craftsman 3000psi and it keeps losing pressure

pressure vessel could have lost pressure hence the water loss

First check your air cleaner for clean filter. If that's clean then ajust your valves. Start with intake and exhaust set at .004 each. I think this will fix your problem. GOOD LUCK FRIEND.

just a sensor, or gague

Sounds like a bad coil. But a sensor like a module or an aging distributor cap and rotor are the most suspect. Take off the distributor cap and see if a white powdery substance is building up scrape it clean with a sharp knife... it may run for a few months best to replace the rotor and distributor cap

ITs hard to diagnose these things over the internet, it could be so many things.
Is this a gradual loss of power? If so; Im sorry to say; that it sounds like its losing compression as it warms up. It is not cost effective to repair the unit.

If the loss of power is more sudden it could be a failing ignition module. Ive even seen spark plugs that quit working when they get hot.

To test this you will need a proper spark tester, laying the spark plug against the head will not provide an accurate assesment, and a can of carb cleaner. Run the unit with the air box cover and filter removed till it fails and immediately give a shot of carb cleaner in the carb and restart. If it starts right up it could be fuel related. IF it doesnt start right up then quickly test for spark. If no spark then its likely the ignition module. If it wont run on the extra fuel and it has spark then it has probably lost compression.

Us start here, remove fuel line from carb. Hope fuel runs out.
Check the direction of fuel filter. There arrows on it. Arrow toward
carb.

fuel pump and or fuel filter issue.
Ck

That small piece of rubber came from the compressor pump, more than likely you have a broken valve or blown head gasket in the pump, that is why it will not build pressure.

The first question is: does it build up pressure in a normal rate of speed? If not....or if it can't keep up with the demand you're putting on it.....it may be the piston ring. I owned an oil-less version Campbell Hausfeld compressor that wouldn't get up to operating pressure....turned out to be a torn plastic piston ring. hope this helps.

de filters clog very fast i suggest put vac in pool put hose over pool attach a wet vac to get water out of hose remove wet vac and vac saves de and water