LLY: Injectors (inner workings and testing)

[05lly2500hd]

How accurate is testing these on a bench compared to installed? Does anyone have pictures of the "guts"of an LLY injector? or have detailed info on how they actually operate?

I've done a return test and found ONE returning fuel, 8ml. Upon taking the entire bank of injectors out, I get two of the four mixed up. So now i don't know which injector was the one returning too much fuel.... I took the two to an local diesel fuel injection shop and had him test the two on the bench only to find that there was little to no difference in return rates.....This all stems from a problem i've been ignoring up until recently as i could not sustain rail pressure. So now i'm kinda

How is the return actually "controlled" ? Upon looking down the return of the injector, there is what looks like a stainless ball or pin..what is this? Is it something that opens and closes for the return or is this what the fuel passes by when it is returning to the tank?

 

[S Phinney]

Return occurs when there is an internal leak and the fuel under pressure returns some instead of going into the cylinder. You shouldn't have any return unless there is a problem starting to occur. There are ball and seats in the injectors and internal seals.

 

[05lly2500hd]

well the first time i did the test...I had one injector returning 8ml of fuel and 0ml for the other 7....upon removing injectors, forgetting which was which and reinstalling....none are returning fuel now............

 

[S Phinney]

Just keep a close check on them for out of the ordinary noises, fuel usage and idle quality.