weekend snowball/injector Identification

[mchampion]

The truck I just picked up had a cold skip and a lot of raw fuel on a cold start (-0 temps).

I knew when I picked up the truck that a glow plug terminal was broken off, and assumed I just needed a new glow plug, so yesterday I removed the plugs. The end of the plug (element) on the cold cylinder (#2) was broken off, so I removed the injector and checked the pre cup to see if I had broken it/if it was still there.

While I had the injector out, I decided to pop test it and see where it was, and it was terrible, nozzle started to.leak at ~1200psi and sprayed at ~1400psi with a ugly pattern and no chatter.

I proceeded to remove the rest of the injectors and test them as well, they all tested clean, popping at ~2100 psi with a nice spray and good chatter.

all the good injectors are stamped with 173, I can't see any numbers on the bad injector. I was told by the PO that the injectors were replaced, but no documentation. I'm assuming these are someones high pop's and was hoping someone might have an idea of where these came from. And also be able to point me in the right direction to get a single injector

[Robyn]

Welcome to T D P

I would recommend you go to a local diesel shop that does the GM injectors and have them set one up for you.

It's an easy job if you have the parts on hand.

Just replace the one and your good to go.

2100 psi is just about where the squirts on the 6.5 should be.

Missy

[mchampion]

Thanks Robyn, I haven't worked on 6.2's/6.5's much since I got out of the service and for some reason I had 1800psi stuck in my head.

[DmaxMaverick]

Thanks Robyn, I haven't worked on 6.2's/6.5's much since I got out of the service and for some reason I had 1800psi stuck in my head.

1800 PSI is the lower end of 6.2L injectors. 6.5L injectors should be 2050 PSI for OEM optimal, with just shy of 2100 PSI with typical (good) remans. Beyond 2100 PSI will begin to see pump life suffer. Higher pressure improves efficiency/atomization, and timing accuracy, but increases load on the pump.

Ultimately, consistency has a much greater affect, compared to just the "pop pressure". I don't recommend mixing batches of injectors, for this reason. Of course, you can, but performance and efficiency may suffer, and it can cause serious mechanical issues if they are excessively poorly balanced. Unless you can locate a replacement injector from the same source as the others, and they are relatively new, a full new set is a much better option. There are many variables involved in injector consistency, including nozzle source/type, shims, bodies (they vary, even within the same brand over time), and springs, which can be a real PITA if they get mixed up. New (or less used) springs will have a much different compression rate than well used. Many rebuilders compensate with shims, which tosses the engineered dynamic of the injector, compared to other injectors. Ideally, these engines should live their entire life with the same set of injectors, only being refreshed from time to time as needed.

[mchampion]

Being this was my first post I probably should have mentioned that I'm a heavy equipment/diesel mechanic, 7 years in the Navy as a SeaBee CM, and 7 years on the civilian side as Field Technician for two equipment dealers.

1800psi being the low end for 6.2 injector specs makes sense as most of the HMMWV's and CUCV's I worked on in the service had the 6.2 in them.

I completely agree that consistency is more important than the Individual injectors "pop" pressure, I wish I could find a way to make customers understand that when they only want to change 1 of there 4 (or 6) out of spec injectors. I typically get "but that's the only one that's skippin"!

The 7 "good" injectors (marked 173) had an average pressure of 2085psi and were all within 4% of that average. If I was rebuilding them myself, I would go for better than an 8% spread, but I'm not going to change them over it when there are other, more pressing, things that need to be done first.

The "bad" injector is completely unmarked, and the finish on the body is different. I assume that it was mixed in somehow when these injectors were installed.

I was hoping to locate an injector from a same source, which is why I asked if anyone recognized the "173" Mark on the injector.

At this point I think I'll just take the bad injector to work with me tomorrow and see if the injector guy our shop uses can rebuild it to match the average of the other seven, run the rest as is for now, and revisit the injectors this summer when cash flow and weather are more cooperative.

Thanks again
Mike

[Robyn]

For now, get a replacement that is as close as you can get to the other 7 and it should be ok.

What really causes issue is having them all over the map.

As Maverick said, consistency is important on these engine.

Cyl to cyl timing can vary a lot with a crappy set of injectors, and this can cause a lot of unwanted stress on crank shaft.

Good luck

Missy