High-pressure car wash water gun will work for a while a stop, what happened?

Not enough water pressure in the hose. It needs to be cleaned from the dust inside.

Water pressure is too high will damage the car paint, waterjet application scenario is used in the cutting of heat easily deformed or deformation-sensitive high-precision materials, such as some fabric, leather, sponge and even steel, etc., the machine through the high-pressure will be rushed out of the water flow, like a knife to cut things apart, so in fact, the water in the high-speed jetting situation is also a lethal force.

Car wash water gun purchase points:

Look at the car wash water gun accessories are complete. High-quality car wash gun accessories should contain at least: faucet connector, hose connector, special hose, water gun four parts, some even with brush nozzle; and cheap car wash gun in order to save costs, often cut corners on the accessories, such as: accessories do not come with a water hose, or with ordinary water pipe instead of a special hose, and some are not even equipped with any fittings.