I have a 1981 Scamper Camper(motor-home) built on a Ford E350 Chassis. It was converted to propane by the previous owner.
My problem is: After I shut down I can smell propane.
Why don't I smell it any other time? and what can I do to fix it?

 

You didnt mention is the propane smell is brief or constant with the engine off. I'm not going to go into the obvious life/safety issues here, my advice is to Identify the entire fuel system and then using a solution of dish soap and water, check all propane plumbing and equipment for leakage. You may need to perform the test a few times by location (engine, fuel lines/regulator, fuel tank) to "catch" the leak as it happens if it is a brief release of gas. Not something to be taken too lightly...

 

The smell is brief after shut down. You have to be paying attention to catch it.