Cat 3116 "hunting" after injector change

[The Bill Collector]

I had something odd happen last Sunday, we did an ash scattering of my Aunt in Commencement Bay and had been idling around for quite some time. It was time to head to the shed, so I fired it up to 2400 and the lead engine (port) sputtered a little, rpm's fluctuated, and finally smoothed out. I was the E.R. yesterday checking stuff and the primer pump on the port engine had unscrewed itself, so I'm sure I was getting a little air in the line. Sorry to hear about your engine issues, I hope I just solved my minor one.

 

[GnrlPatton]

I had something odd happen last Sunday, we did an ash scattering of my Aunt in Commencement Bay and had been idling around for quite some time. It was time to head to the shed, so I fired it up to 2400 and the lead engine (port) sputtered a little, rpm's fluctuated, and finally smoothed out. I was the E.R. yesterday checking stuff and the primer pump on the port engine had unscrewed itself, so I'm sure I was getting a little air in the line. Sorry to hear about your engine issues, I hope I just solved my minor one.

I've had that happen before too, now it's one of the things I always check when I go down below. Valve turned off and knob tightened.

Sorry about your Aunt.

Kevin

 

[The Bill Collector]

I've had that happen before too, now it's one of the things I always check when I go down below. Valve turned off and knob tightened.

Sorry about your Aunt.

Kevin

Thanks, Kevin... She lived her adult life in Tacoma after graduating Puget Sound University and her house was up on the hill to the north of Stadium HS so my Mom wanted her ashes spread below on Commencement.

 

[Zooomin]

Nope, we got it to the point where it was acceptable, but it was always there. When I first noticed it and started this thread, it was really bad, with a 2-300rpm fluctuation. We got it down to maybe 20-30rpm, but never to 0. I just got back from a big trip a few weeks ago, and during the trip it got worse, it's probably now 150rpm fluctuation. Another symptom as well is that it's smoking a lot, even after being warmed up.

I reached out to my mechanic when I got back, and he came back with this:

"I'm sorry to hear this. I do have an extra governor and rack for your engine model/HP that I can install. I believe this is the problem with your engine. If it's fine with you we can come up and get these parts changed out. The parts would be of no cost to you and are used.. They came out of an engine with 800 hours that failed due to an oil loss issue about 3 weeks ago."

I'm going to have him do the replacement and see if that is indeed the problem. Last year we considered swapping the rack and governor from the starboard motor over to see if the hunting problem went away, but I was hesitant to touch the good running motor. He said he's booked out a few weeks, so once we're able to make the swap, I'll update this thread with the results.

Kevin

Hi Kevin,

You may recall from the Official 370 EC thread that I have a very similar surge as you. I’m still chasing it down. I was curious if you found a solution to your surge, and if you tried changing the governor and or rack. Any information would be helpful.

Thanks for your time.
David

 

[GnrlPatton]

Hi Kevin,

You may recall from the Official 370 EC thread that I have a very similar surge as you. I’m still chasing it down. I was curious if you found a solution to your surge, and if you tried changing the governor and or rack. Any information would be helpful.

Thanks for your time.
David

I'm trying to recall everything that we did, but the hunting never went away 100%. It's significantly better though, so I've not done any more on it. Plus I only used the boat once last summer, we had to take a pause on boating since my wife was going through chemo for breast cancer.

I'm not sure if it's still happening or not, but I'm thinking we got it down to an acceptable, and barely noticeable level.

From my conversations with my mechanic in email, this is what I recall trying out:
- Initial fuel injector replacement (which started the symptoms)
- Replace 1 failed injector
- Air bubble check in the fuel return line
- Replacement of the injector pump housing check valves
- Oil screen cleaning
- Dashpot adjustment check
- Install a new governor rack (he had a spare from a recent rebuild and swapped it in for just labor)

If I can think of anything else we tried, I will update here.

Sorry can't be of more help. Do you know what triggered your symptoms?
Kevin

 

[Zooomin]

I'm trying to recall everything that we did, but the hunting never went away 100%. It's significantly better though, so I've not done any more on it. Plus I only used the boat once last summer, we had to take a pause on boating since my wife was going through chemo for breast cancer.

I'm not sure if it's still happening or not, but I'm thinking we got it down to an acceptable, and barely noticeable level.

From my conversations with my mechanic in email, this is what I recall trying out:
- Initial fuel injector replacement (which started the symptoms)
- Replace 1 failed injector
- Air bubble check in the fuel return line
- Replacement of the injector pump housing check valves
- Oil screen cleaning
- Dashpot adjustment check
- Install a new governor rack (he had a spare from a recent rebuild and swapped it in for just labor)

If I can think of anything else we tried, I will update here.

Sorry can't be of more help. Do you know what triggered your symptoms?
Kevin

Thank you for all the information. More importantly, I’m sorry to hear about your wife. Hopefully by now she’s doing much better. Some folks get bad reactions just to the treatment alone, some breeze right past it without side effects.

To answer your question, I purchased the boat with the surge issue. My boat came with no records or owner manuals of any kind. I got to know the boat about a year before I purchased it from a good friend, who only had it for a year. He didn’t know much as this was his second and much smaller boat.

I noticed the surge early on, and my thinking was “My mechanic can handle this.” Wrong! Even the local and very smart factory CAT marine mechanic is somewhat stumped. However, he is recommending a new governor (currently $3500). Two other smart marine mechanics are pointing to the governor as well, and have advised to get a reman or new one. At this time no reman governors are available. I bought the boat with 1030 hours on the motors. I’m told that everything looks original, including the injectors. Also, the rack can be one potential cause of surge, but apparently my rack was checked by CAT and is ok.

It sounds like you did not replace your governor with the one your mechanic mentioned.

Like your surge, my surge is not so bad, but it is pretty annoying. I might swap my known good governor in to see if that solves the issue. In that case, if it works, I will just bite the bullet and buy the new governor. I will let you know.

Thank you for spending the time to respond.

All my best to you and your wife,
David

 

[ttmott]

Only one thing can cause surging and that is fuel.
The injector rack will constantly modulate to maintain the engine at the load set point (throttle position).
The other thing is if fuel pressure isn't stable then hunting can occur. The injector pump on these engines is a reciprocating piston that relies on those little check valves, spring loaded pressure regulator, and a pulse dampening diaphragm to pressurize and stabilize the fuel pressure.
If the governor inside of the pump is malfunctioning it can also cause surging as it also controls fuel.

 

[Zooomin]

Only one thing can cause surging and that is fuel.
The injector rack will constantly modulate to maintain the engine at the load set point (throttle position).
The other thing is if fuel pressure isn't stable then hunting can occur. The injector pump on these engines is a reciprocating piston that relies on those little check valves, spring loaded pressure regulator, and a pulse dampening diaphragm to pressurize and stabilize the fuel pressure.
If the governor inside of the pump is malfunctioning it can also cause surging as it also controls fuel.

Thank you for this. I’m still learning about the chain of command for fuel delivery and your view of this helps. I do believe uneven fuel pressure/delivery, caused by who knows, is the culprit.

Heat seems to have a lot to do with the surge, which only presents itself after a five minute warm-up in neutral.

Does swapping out the governor for a known good one from my other motor (to see if the problem goes away) make sense? I am trying to avoid a $3500+ dice roll on a new governor.

 

[ttmott]

Thank you for this. I’m still learning about the chain of command for fuel delivery and your view of this helps. I do believe uneven fuel pressure/delivery, caused by who knows, is the culprit.

Heat seems to have a lot to do with the surge, which only presents itself after a five minute warm-up in neutral.

Does swapping out the governor for a known good one from my other motor (to see if the problem goes away) make sense? I am trying to avoid a $3500+ dice roll on a new governor.

It's odd a Cat mechanic can't get to the bottom of the issue.... It will be costly to swap the injector pumps because the entire rack needs to be reset (three times if borrowing from the other engine). It may be a better plan to have a mechanic travel from another Cat dealer/service center if you get a warm fuzzy after talking to them. The 3116's on my 400DA Sundancer were struggling to have a quality idle when I purchased the boat. My mechanic who previously was a diesel mechanic for our local Cat service center knew exactly what to do (in my case the little check valves needed replacing) and wham bam was done and also set up the rack. He had all of the CAT tools and instrumentation to evaluate everything on the engines. As it ended up the pressure gauge he used saw the pressure fluctuations in concert with the fuel pump with a lower than spec pressure and knew it was the check valves..

One thing - did they check for air in the fuel return line? If combustion gases leak past the injector seat and end up in the feed circuit of another downstream injector the exact issue can occur. It's not a big deal to have the seats reamed and injectors re-set.

 

[Zooomin]

It's odd a Cat mechanic can't get to the bottom of the issue.... It will be costly to swap the injector pumps because the entire rack needs to be reset (three times if borrowing from the other engine). It may be a better plan to have a mechanic travel from another Cat dealer/service center if you get a warm fuzzy after talking to them. The 3116's on my 400DA Sundancer were struggling to have a quality idle when I purchased the boat. My mechanic who previously was a diesel mechanic for our local Cat service center knew exactly what to do (in my case the little check valves needed replacing) and wham bam was done and also set up the rack. He had all of the CAT tools and instrumentation to evaluate everything on the engines. As it ended up the pressure gauge he used saw the pressure fluctuations in concert with the fuel pump with a lower than spec pressure and knew it was the check valves..

One thing - did they check for air in the fuel return line? If combustion gases leak past the injector seat and end up in the feed circuit of another downstream injector the exact issue can occur. It's not a big deal to have the seats reamed and injectors re-set.

Thank you for all of this. I’m grateful for your time, and I am going to investigate all of this. I had no idea the racks would need to be adjusted after changing governors. Wow.

We did look for air in the fuel return and none were present.

Regarding the possibility of trying a different mechanic, this is a great suggestion. There actually is another CAT marine mechanic located about 60 miles south. A friend who has 3126 motors near me swears by him, so perhaps I can get him to look at my motor.

I’m curious if you recall a roughly five minute delay before the idle issues kicked in with your ex 3116s. Were they rough idling, oscillation sweep, or? I have the oscillation.

Thank you again for spending time on this. It is greatly appreciated.

David

 

[GnrlPatton]

Thank you for all the information. More importantly, I’m sorry to hear about your wife. Hopefully by now she’s doing much better. Some folks get bad reactions just to the treatment alone, some breeze right past it without side effects.

To answer your question, I purchased the boat with the surge issue. My boat came with no records or owner manuals of any kind. I got to know the boat about a year before I purchased it from a good friend, who only had it for a year. He didn’t know much as this was his second and much smaller boat.

I noticed the surge early on, and my thinking was “My mechanic can handle this.” Wrong! Even the local and very smart factory CAT marine mechanic is somewhat stumped. However, he is recommending a new governor (currently $3500). Two other smart marine mechanics are pointing to the governor as well, and have advised to get a reman or new one. At this time no reman governors are available. I bought the boat with 1030 hours on the motors. I’m told that everything looks original, including the injectors. Also, the rack can be one potential cause of surge, but apparently my rack was checked by CAT and is ok.

It sounds like you did not replace your governor with the one your mechanic mentioned.

Like your surge, my surge is not so bad, but it is pretty annoying. I might swap my known good governor in to see if that solves the issue. In that case, if it works, I will just bite the bullet and buy the new governor. I will let you know.

Thank you for spending the time to respond.

All my best to you and your wife,
David

Thanks David. She's doing well now, just starting on radiation (5 more weeks worth, every day) and the doctors all say positive things about her long term diagnosis.

So my mechanic did swap in the other governor that he had, I resisted him swapping governors from my other engine since it was running perfectly and I didn't want to mess that up and then have 2 poorly running engines.

Mine also only manifests once the engines are at operating temps, when I first start up, they purr like they should.

I am leaning towards the check valves as Tom mentioned, all of my research pointed to those and since they are an easy fix, shouldn't cost you much to do them.

 

[ttmott]

Thank you for all of this. I’m grateful for your time, and I am going to investigate all of this. I had no idea the racks would need to be adjusted after changing governors. Wow.

We did look for air in the fuel return and none were present.

Regarding the possibility of trying a different mechanic, this is a great suggestion. There actually is another CAT marine mechanic located about 60 miles south. A friend who has 3126 motors near me swears by him, so perhaps I can get him to look at my motor.

I’m curious if you recall a roughly five minute delay before the idle issues kicked in with your ex 3116s. Were they rough idling, oscillation sweep, or? I have the oscillation.

Thank you again for spending time on this. It is greatly appreciated.

David

warm unstable idle and the engine was noisier than the other. It made she same power as the other engine during sea trials when I bought the boat. Then when baselining the engines when I got the boat home, my mechanic picked up on the issue.
One of the check valves - the pump backflow check is buried deeper into the pump (if I remember correctly) but still needs to be changed. The check valves were like eight dollars each; but that was at least ten years ago.

 

[Zooomin]

Thanks David. She's doing well now, just starting on radiation (5 more weeks worth, every day) and the doctors all say positive things about her long term diagnosis.

So my mechanic did swap in the other governor that he had, I resisted him swapping governors from my other engine since it was running perfectly and I didn't want to mess that up and then have 2 poorly running engines.

Mine also only manifests once the engines are at operating temps, when I first start up, they purr like they should.

I am leaning towards the check valves as Tom mentioned, all of my research pointed to those and since they are an easy fix, shouldn't cost you much to do them.

Thank you and I’m glad to hear she’s doing better. Radiation is very good and targeted now. It can also be draining. It is not easy being in your shoes.

I really appreciate your recall on what you did in relation to the surge. It’s great that you have, for the most part, won the surge war. I believe my mechanic did check at least one check valve and replaced a screen, but to no avail. I will post more on what I learn, soon.

I hope you can get back to boating again, soon.

Thank you again so much for all of your help and suggestions.

David

 

[Zooomin]

warm unstable idle and the engine was noisier than the other. It made she same power as the other engine during sea trials when I bought the boat. Then when baselining the engines when I got the boat home, my mechanic picked up on the issue.
One of the check valves - the pump backflow check is buried deeper into the pump (if I remember correctly) but still needs to be changed. The check valves were like eight dollars each; but that was at least ten years ago.

Thanks so much for this. Interesting information. I will compare, contrast and continue to investigate. By the way I have been eyeing the 44’ version of your boat. I have always had fly bridge boats until this one, which I really do enjoy. Having one level makes everything so easy and convenient to operate, but I do miss being up high on long runs.

David

 

[Carver370]

I have been having the same issue with a slight surge at idle once the engine is warm. I did not have a great experience with one CAT tech, but then had a great experience with another from a different location.

We did "check" the check valves but I was never convinced that the first guy knew what he was even looking at. I wanted to just replace them, but he said there was no need.

I still have a slight surge at idle after a run and this engine has always been a little louder than the other. My issue seems very similar to ttmott's on my 400. @ttmott do you recall having a diagram of exactly where they were located?

 

[Zooomin]

I have been having the same issue with a slight surge at idle once the engine is warm. I did not have a great experience with one CAT tech, but then had a great experience with another from a different location.

We did "check" the check valves but I was never convinced that the first guy knew what he was even looking at. I wanted to just replace them, but he said there was no need.

I still have a slight surge at idle after a run and this engine has always been a little louder than the other. My issue seems very similar to ttmott's on my 400. @ttmott do you recall having a diagram of exactly where they were located?

Good question. I checked with my mechanic and he told me he did change out the easiest one to get to, and it included a new spring. No change in my particular surge.

 

[ttmott]

Good question. I checked with my mechanic and he told me he did change out the easiest one to get to, and it included a new spring. No change in my particular surge.