Marine 3606 electronic injectors problem

Had the Caterpillar marine technician troubleshoot our port engine, due to running very rough. He determines the engine is running on #1 and #6 cylinder only, and recommends replacing the other 4 injectors.
We only had 3 injectors available so we decided to replace two of them and see how what results we get.
After replacing #2 and #5, the engine starts running perfect.
We start the starboard main engine in hopes to get underway, but now the starboard engine is running rough.
The Caterpillar tech tells us that we have the identical symptom as we did on the port engine, only operating on #1 and #6. Since we only had 1 injector left, we decided to replace #2 and see what happens. Replaced #2 and the now the engine runs great on all 6. Load tested both engines with good results, let the vessel get underway and has been running good for over a day now. If anyone have any thoughts that would explain how replacing 1 injector somehow made the engine fire on all 6, please post them, I would love to hear from you.
Thank you!

I’ll bet the guys that made the ECU know

1 Like

I worked with 3612s and the first c280s from 2002 to 2009. We would lose an injector from time to time with no explainable reason from Cat. With a load on the engine, the loss of one injector would shoot the exhaust temps through the roof. If you changed more than 2 injectors, the trim had to be reset. This can only be done with a cat computer.
There was time that Cat couldn’t keep up with our fleet so each vessel was issued a Cat laptop.

sound like Cat trying to scam you guys and sell you two whole sets of injectors

besides how on earth can a big engine like that even idle on only two injectors firing?

My guess (and yes, it’s a complete guess) is that the ECM has an EGT deviation feature that derates the engine, including cutting out injectors when the deviation setpoint is reached. That’s the only thing that makes sense to me based on the observations he’s reported

The pyro readings verified that we were running on #1 and #6 on both engines (1 and 6 in the 300’s F and 2, 3, 4 and 5 in the 80’s F)
The engines idled at 400 rpm as usual, but very rough, once we engaged them they bogged down to the mid 200’s and died not too long after.
I don’t believe the injectors we removed were bad, but I’ll verify that tomorrow when they get back, I’ll cycle one of them in at a time and keep them as spares if they check out good. They have about 7000 hours and I understand they should last into the 20K’s
Once I rule out that the injectors we replaced were not bad, I can think of a few possible scenarios:

  1. The process of replacing the injectors meant draining the fuel and re-priming with fresh fuel.
  2. The ECM’s for some reason decided not to fire the same set of cylinders on both engines, 2,3,4 and 5
  3. Updating the trim numbers on the ECM might have reset something and caused it to start firing on all 6 cylinders.

I’ll update once we’re done checking the 3 injectors

The fact that 2 different but equally programmed ECM’s reacted in the exact manner, by cutting out the same set of cylinders on both engines, makes me agree that the ECM’s may have performed as intended.

My guess is that the computer knows it can’t safely run on only certain cylinders so when one goes bad it automatically shuts down others to balance the engine.

Bad data

I seriously doubt those readings are anywhere near reality. Even if they were in C (which they probably are) 300C is closer to idle temp and 80C is closer to low coolant temperature for an engine that has been running for any amount of time.

1 Like

which cat dealer, which port of call?