OK you truckers...

twostick said:
You need to find someone with a CAT laptop that can actually interpret the data it reads. If the problem is ambient temp related, what is the Intake Air Temp sensor saying? Too high and it derates, so if the sensor is lieing to the ECM without throwing a code, that could be part of your problem. Charge air cooler could be an issue also if it's full of bugs and dirt.

Instead of swapping #4 injector, you should exchange it to a different hole to see if the problem follows the injector. If it doesn't, it's not the injector.

CAT injectors have trim codes that have to be entered in the ECM. If the original injector required a larger trim percentage than the replacement or vice versa, it could adversely effect the idle.

Also a cut out test might show a particular injector contributing less and failing when in fact it was the injector before it in the firing order that over fueled. The test compares the RPM drop between pulses and how much fuel it needs to add to maintain test RPM per cylinder. If #2 overfuels enough to carry the target RPM past the #4 event then #4 needs to contribute very little, but #1 has to add more fuel trim than the program predicts to bring the target RPM back in the window for its event. #4 shows bad when the problem is actually at #2.

Wiring harnesses can become an issue on engines with a lot of time on them, especially the connections at the injector itself. IIRC they run about 90 volts so they can arc and burn the connectors.

Kevin
Click to expand...


When this problem first showed up, I think I checked every available readout on my scan gauge while it was acting up and none of them were abnormal, but I'll double check the air intake temp during this week's trip.

IMG_9857.JPG


Can't move the injector around to see where the problem goes since it needs to be on a dyno to make it act up while testing, and the diagnostic budget has already been exceeded.

I'm aware of the trim code issue and suspect it as the reason the truck runs rough with the reman injector installed.

The tech at Pittsburgh Power who looked at it wasn't some oil & lube newbie. He writes new programs for diesel ECM's and was checking all the info coming out of the computer during all the testing. There were some values that it was displaying on the screen in the control room that gave an idea of what each injector was doing and he was pretty certain that #4 was totally dead at times. The fact that it comes and goes should rule out a mechanical issue. He also had two sight glasses installed in the fuel lines, and that's where he was seeing the air in the fuel.

I guess that there is always the possibility of a harness issue, but I'm assuming that CAT replaced the harnesses when the engine was remanned in 2011. It's a CAT crate engine, with under 700K miles on it. Everything I can see when I have it apart looks fine.


The injector that I bought off eBay that was described as likely to be remanned is crap. It's as used as used can be, plus it sat somewhere dirty for at least a decade. It's going back where it came.

eBay listing photo:
s-l1600.jpg


Actual part:
img_9859.jpg


IMG_9858.JPG



So, I put the real reman injector back in and I'll live with the rough idle for a week. If by some miracle it fixes the problem, I'll bring it to a shop to have the correct code put in the ECM.

Over the last couple years, at least three people have called into the Trucking show that I listen to on Sirius/XM with similar symptoms on CAT engines. So far there have been no calls about solving them. One caller claimed to have replaced everything: ECM, injectors, fuel lines, fuel pump, wiring harness, sensors, etc and the problem persists. Last week I stumbled upon a post on a diesel message board about the injector seats in the heads being improperly machined from the factory, allowing combustion pressure into the fuel rail and causing the bad stumble when pulling hills. He was specifically talking about C15's, which is what the radio callers all had, and that was probably the cause of their problems, and why changing all those parts didn't fix the one. May not pertain to the C12 at all, but if I didn't mention it there's also the possibility of a cracked head. I think I also heard about a bad injector allowing compression to get into the fuel system. That was on a Cummins N-14, though I don't see why it couldn't happen to a CAT too.

I'm going to book another one-week, out and back trip and see what happens. If it's still no good, then maybe I'll park it for a couple weeks and see if the weather cools off a bit so I can get a couple more runs in before the registration expires.

Jeff
 
bigmoparjeff said:
When this problem first showed up, I think I checked every available readout on my scan gauge while it was acting up and none of them were abnormal, but I'll double check the air intake temp during this week's trip.

View attachment 397420

Can't move the injector around to see where the problem goes since it needs to be on a dyno to make it act up while testing, and the diagnostic budget has already been exceeded.

I'm aware of the trim code issue and suspect it as the reason the truck runs rough with the reman injector installed.

The tech at Pittsburgh Power who looked at it wasn't some oil & lube newbie. He writes new programs for diesel ECM's and was checking all the info coming out of the computer during all the testing. There were some values that it was displaying on the screen in the control room that gave an idea of what each injector was doing and he was pretty certain that #4 was totally dead at times. The fact that it comes and goes should rule out a mechanical issue. He also had two sight glasses installed in the fuel lines, and that's where he was seeing the air in the fuel.

I guess that there is always the possibility of a harness issue, but I'm assuming that CAT replaced the harnesses when the engine was remanned in 2011. It's a CAT crate engine, with under 700K miles on it. Everything I can see when I have it apart looks fine.


The injector that I bought off eBay that was described as likely to be remanned is crap. It's as used as used can be, plus it sat somewhere dirty for at least a decade. It's going back where it came.

eBay listing photo:
View attachment 397450

Actual part:
View attachment 397446

View attachment 397445


So, I put the real reman injector back in and I'll live with the rough idle for a week. If by some miracle it fixes the problem, I'll bring it to a shop to have the correct code put in the ECM.

Over the last couple years, at least three people have called into the Trucking show that I listen to on Sirius/XM with similar symptoms on CAT engines. So far there have been no calls about solving them. One caller claimed to have replaced everything: ECM, injectors, fuel lines, fuel pump, wiring harness, sensors, etc and the problem persists. Last week I stumbled upon a post on a diesel message board about the injector seats in the heads being improperly machined from the factory, allowing combustion pressure into the fuel rail and causing the bad stumble when pulling hills. He was specifically talking about C15's, which is what the radio callers all had, and that was probably the cause of their problems, and why changing all those parts didn't fix the one. May not pertain to the C12 at all, but if I didn't mention it there's also the possibility of a cracked head. I think I also heard about a bad injector allowing compression to get into the fuel system. That was on a Cummins N-14, though I don't see why it couldn't happen to a CAT too.

I'm going to book another one-week, out and back trip and see what happens. If it's still no good, then maybe I'll park it for a couple weeks and see if the weather cools off a bit so I can get a couple more runs in before the registration expires.

Jeff
Click to expand...
I bet that it’s the injector seat.
 
3175375 said:
I bet that it’s the injector seat.
Click to expand...

This is what a bad one looks like. The injector itself will also be eroded where it contacts the seat if everything started out new together.

You said something about missing or mangled Orings too. Make sure they are all Genuine Cat. I've seen aftermarket ones that don't stand up and they can cause no end of problems.

Kevin

20180125_153456.jpg
 
commando1 said:
I never asked.... How many horsepower?
Click to expand...
It's flashed for 460, turbo and injectors are for bigger than that and when it was rebuilt they advanced the cam timing/shims for.more cylinder pressure and throttle.response. it works well for my putting around. Mid to high 30s for manifold pressure, never goes over 850° on turbo out.
Safe.
 
Last edited:
twostick said:
This is what a bad one looks like. The injector itself will also be eroded where it contacts the seat if everything started out new together.

You said something about missing or mangled Orings too. Make sure they are all Genuine Cat. I've seen aftermarket ones that don't stand up and they can cause no end of problems.

Kevin
Click to expand...

My seats looked pretty decent. I couldn't find a seat cleaning brush specific for the big CATs, so I rigged up a few different size wire brushes to get everything cleaned up nice. There were no signs of damage on the seats of the injectors, just the small, bottom o-rings were MIA.

I didn't spend the big bucks on CAT o-rings, since this thing won't ever see more than another 20K miles. I bought a set of US made o-rings on ebay. They looked to be good quality and actually had part numbers printed on the two larger size rings.

I booked a short trip to Connecticut and back for tomorrow, so I'll know soon if the new injector makes any difference. It'll be about 90 degrees out and there are plenty of hills on I-84 to get it to act up if it's going to.

Jeff
 
commando1 said:
Manly hands. As they should BE. No gloves needed.
I hope you have a livestock trough outside with lots of Lava and Dove.
Click to expand...
Just about kicked the last of my Cherry bomb. Back to regular hand cleaners.
3175375 said:
Only thing missing is blood...
Click to expand...
The excessive grease kept anything from cutting. Line just has to leak right in the spray pattern from u-joint.
 
commando1 said:
After leaving Hartford and heading north to the Mass Pike?
Click to expand...

From Danbury going east to Hartford. Now that you said something though, I just realized I won't be going past Danbury. I'll be taking US 7 south to I-95. There are also some decent hills on I-78 and I-287, so I'm sure I'll find enough to test things.

Jeff
 
bigmoparjeff said:
My seats looked pretty decent. I couldn't find a seat cleaning brush specific for the big CATs, so I rigged up a few different size wire brushes to get everything cleaned up nice. There were no signs of damage on the seats of the injectors, just the small, bottom o-rings were MIA.

I didn't spend the big bucks on CAT o-rings, since this thing won't ever see more than another 20K miles. I bought a set of US made o-rings on ebay. They looked to be good quality and actually had part numbers printed on the two larger size rings.

I booked a short trip to Connecticut and back for tomorrow, so I'll know soon if the new injector makes any difference. It'll be about 90 degrees out and there are plenty of hills on I-84 to get it to act up if it's going to.

Jeff
Click to expand...

Good luck with the Orings. I saw a set that came out of a Series 60 that had a bad miss after changing injectors. They were hanging on the injectors after they were removed, all the shape gone and in the process of going back to whatever goo state they were molded from.

Kevin
 
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