Adapter for in cylinder pressure transducer in a 96 Mercury Grand Marquis

Anyone know what adapter I would need to screw on to the end of my compression hose for doing in cylinder pressure transducer traces? I've never actually done one of these readings before. I tried today to screw my compression hose into a 96 Mercury Grand Marquis and for about 2 hours, I tried everything I could think of and never could get the fitting to screw into the spark plug hole. I verified the thread pitch was the same, I verified the OD was the same with a set of calipers, but nothing I could do could make that fitting screw into the somewhat difficult to reach spark plug hole. Not sure if Ford may have some sort of proprietary hole design or what. I'm using a cheap Harbor Freight compression tester and a little 500 PSI transducer rigged up to be a cheap in cylinder pressure transducer tool. I'm not expecting great results from my cheap setup coupled with my inexperience, just want to play around with it and learn how to do this. But pretty much got the wind knocked out of my sails today spending a couple of hours and never even able to screw a fitting into a hole.

Definitely frustrating. Pretty sure the 4.6L uses the same old M14 standard that most other engines use... Most of the HF tester sets I can find have an M14 adapter.

Any chance the cylinder you chose has a repair thread insert in it? :huh: This wouldn't be the first 4.6L to need a thread repair after blowing a plug out.

Thanks. I checked two different cylinders and wasn't able to thread into either of them. But, I suppose it's possible both may have been repaired in the past. I wonder also if I was using a metal tube instead of the rubber tube that came with my kit, if that would help. It was sadly funny when I went back into the house.... my wife said, "did you get much done with Rose's car?" I said, "no... nothing at all actually. I spent two hours trying to insert a screw into a hole, and never could do it."

If that rubber hose is curved that could be your problem.

Thanks. I'll look for a metal pipe.