TBI Fuel injector oil ring question - 1993 C1500

[SKFengineer]

After 206,000 miles on my TBI 305 I'm rebuilding the TBI unit for the first time. I'll be doing most of the ultimate TBI mods while I'm in there but I ran into an odd little thing. On other TBI units I've worked on and the one in the thread link attached below there are metal rings that go under the large O-rings on the body of the injector in the injector pods. On my unit tonight when I pulled the injectors there was no such metal ring only the O-rings. I bought the rebuild kit for this unit and it has the metal rings so I have two questions. One at some point did GM do away with the metal rings and just use the O-rings. Second if the kit came with metal rings I'm assuming I should use them with the O-rings included in the kit vs. just using the O-rings alone. I've owned this truck for last 136,000 miles of the it's life and to my knowledge no one has ever cracked open the TBI unit so this is odd to me, does anyone have any thoughts on this?


Here is a link to modifying and rebuilding the TBI unit, he has posted tons of pictures and about half way down there is a picture that shows these metal rings as he's preparing to install the injectors...

http://www.gmc4x4.com/topic/1035-1991-57l-bored-tbi-upgrade-write-up-warning-lots-of-pics/

Thanks for your help.

 

[1995z71]

When I rebuilt my 1995 throttle body it did not have the metal rings so i didn't install them during the rebuild. Maybe they were only present in earlier years?

 

[SKFengineer]

Okay I guess my only concern with using just the O-rings is was there a different part number for the injector pod used between the earlier and later years? Meaning was there a different grove machined where the O-ring goes one design vs. the other that would require the use of one solution over the other. It's funny I never considered my TBI to be part of a "later" design but I suppose since they started going away in 1996 it was towards the end of the TBI production. I'm hoping to bolt things together tonight so we'll see what happens

 

[SKFengineer]

I may have answered the question on my own. Thinking that there may be a difference between the earlier and later years I remembered I had an old unit from a van tucked away in the corner of my garage. That unit has the metal backing ring so I measured the depth of the step in the injector pod and there is in fact a difference between the two units. The newer unit from my '93 truck is not as deep as the older unit with the backing ring. For this reason I left out the rings when I reinstalled the injectors, plus to be honest it's been fine without them for the last 206,000 miles so what the heck. The system is back together on my workbench, tonight I'll install and test the system. If anything fails related to the O-rings I'll post here later.