I need to do a compression check on my 2014 F150 with a coyote 5.0 engine. I am having trouble getting my hands on the correct adapter to thread into the spark plug hole, I have 3 different compression tester sets with a lot of different adapters but none thread into the engine. All internet searches tells me it's a M14 x 1.25 14mmm long reach and I bought one of these off a snap on truck but it still seems the thread is not correct. I stopped in to speak with the local Ford service manager and he told me it's a special adapter only available to Ford mechanics and you can't buy it online. I'm having a hard time believing this, can anyone enlighten me?