The debate about using infrared heat guns vs. sticking a thermocouple in the exhaust manifold for checking cylinder temps on a 6.7 Powerstroke has me wondering if the old school way is still the most reliable way to catch a lazy injector early, or if I'm just set in my ways because I've been doing it that way since 2012 and the new tools feel like guessing games to me, what do you guys think?

I got into an argument with a younger tech last week because he swore the infrared gun was faster and just as accurate, but I pointed out that on my last EGR cooler delete job the thermocouple caught a 60 degree difference between cylinders 2 and 3 that the gun totally missed because it was reading surface temps from the heat wrap, and now I'm second guessing myself because maybe I just didn't use the gun right, so has anyone else run into this situation where the new method missed something obvious?

3 comments

3 Comments

gibson.elizabeth11d ago

Stick with the thermocouple for injector diagnostics. I've had the same thing happen with a 6.7 where the infrared gun showed even temps across the manifold, but the thermocouple read a dead miss on cylinder 5 that was 80 degrees cooler. The heat wrap and radiant heat from the turbo fool the gun every time. For a quick pass to see if something is obviously wrong the gun is fine, but when you're trying to catch a lazy injector before it takes out a piston, go old school and drill that thermocouple in.

rowanellis11d agoTop Commenter

Is it really that serious though? I mean sure if you're building a million dollar race motor or something, maybe. But on a daily driver truck that's got 150k on it, chasing an 80 degree difference with a thermocouple seems like overkill. Most of the time the infrared gun will tell you if something is way off, and if it looks good across the board, the injector is probably fine for another 20k miles. I've seen guys pull injectors based on thermocouple readings that were 50 degrees off and the injector tested perfect on the bench. Could be an exhaust leak or a random cylinder running lean for half a second while the data was being collected. Are you really seeing catastrophic failures from missing that tiny temp spread?

piper91211d agoMost Upvoted

Buddy of mine caught a #4 injector going bad with a thermocouple after his gun said everything was fine, @gibson.elizabeth.