NAPA, O'Rielly, or Amazon should have the proper adapter. You need a common pressure tester, plus the appropriate adapter. They do make diesel testers, which are designed for much higher pressure (over 1000 psi), but ive got along fine for many years with a cheap gas engine type after I fitted a high pressure gauge and high pressure schrader valve. I always meant to buy a genuine diesel tester, but as this one hasnt blown up I just keep using it. Typically, you will never see over 500 psi. Only way to go much higher is if some combustible gas got into the chamber and detonated, but I dont know if even a diesel tester could handle the kind of pressure of a combustion explosion, which could well exceed 5000 psi. I always stay behind something during a compression test when I crank a diesel, I dont want to be hit with shrapnel should something "pop".