well as many of you have read, I have a compression knock on the #5 cylinder. I read somewhere that you can diagnose injectors by using an infra read temp detector so when I was at harbor freight the other day I noticed they had one. I read the package and they claim accuracy of + or - 2% so I picked it up.

I did my measurments on a warm start, then I ran it around the block with some full boost accelerations. When I did the second measurment the egt was about 600 deg F. All temps are in degrees F.

warm start Hot run

#1 167 175
#2 182 249
#3 188 266
#4 191 268
#5 188 254
#6 181 240

If I understand correctly, #1 may be clogged and #3 and #4 may be dribbling. Injector guru's please comment. So it appears I need new injectors. With the truck stock except gauges can I run Mach 1.6 with out grenading my aging auto tranny? I don't have a boost fooler so I would be defueling at 18psig. Would this hold the hp in acceptable limits if I don't floor it? I priced new injectors and they will run the same as the Mach 1.6 units new. I haven't had any luck getting a used set that is any good so far. Comments?

 

#1 has the fan blowing on it and cools the manifold to some degree. I've played with that at work and usually find #1 considerably more cool than the rest. If you are going to be changing the injectors you may want to run a compression test while you have them out. Fortunately you're running stock for most scored cylinders I've encountered have been on modded trucks. Seems to always be 5 or 6. Another "at home" thing you can do is to swap the #5 injector with another and see if the noise moves with the change.

 

Hmmmm, I never considered the fan blowing on #1. I read some where that the temps should be within 10 deg of each other, if that is the case I am missing the boat. You probably have to have special adapters to run a comp test on this motor, anouther thing to look for. Great idea on swapping the injector to anouther hole. That should rule out any other problems.