Injector Life Expectancy

[Rawze]

(12-01-2016 )Hammerhead Wrote:  

(12-01-2016 )Rig Wrench Wrote:  I've done all 6 in 100k on my 871. I have a theory that at the power level it's at the extended duration is taking its toll. I back up this claim with absolutely nothing, just all that makes since. Started getting a lot of rumputy rump on start up. Checked for bubbles, had on 3 front cylinders. shortly after systems arose again, back 3 replaced and problem solved. Only has just over 100k miles still, total

Help me understand your thought process...

The injectors are cam driven on an 871. (To me) That means that the injector travels 100% top to bottom every second rotation of the crankshaft. There are no electronics on the actual injector, the timing and metering are done externally. The only difference on the injector cycle is the amount of fuel volume in the metered & timing portion of the injector to control timing & injected volume. If I am understanding this correctly, then the engine work load plays zero effect on the number of cycles that the injector should theoretically last.
Yes I understand work/torque load equals heat, and heat shortens the life expectancy of intricate working components like injectors...but besides that, should all else not be equal?
If not, then what am I missing?

Your missing the heat factor. I have seen a many of clogged DPF can and/or exhaust restrictions, overspooling turbo's from bad deletes or bad sensors, etc. kill injectors on CM871's. Symptoms of cooked injectors,.. rough idle, and quite leaky when tested.

If you do an injector leak test, and one or more is barely leaky,.. and very hard to find when wrenching the engine,.. it is not likely to cause any problems or fuel mileage issues,.. but if you can find it fairly easily by wrenching the engine,.. it is definitely bad.

I typically will not tell someone to replace a $600+ injector unless it can be confirmed it is bad without question, or they are very old (more than 6000+k and you are having significant rough idle and/or engine issues already. I have seen a lot of trucks with slightly leaky injectors (can't find them when wrenching the engine but leak a tiny bit when cranking) that don't have idle issues with really good fuel mileage and not have any issues with them whatsoever.