Official Caterpillar3116/3126 Thread

So if you have air in the return, the issue is in the injectors ? The cups? Both?

I would think injectors can be 3rd rebuilt cheaper/faster?
 
dtfeld said:
So if you have air in the return, the issue is in the injectors ? The cups? Both?

I would think injectors can be 3rd rebuilt cheaper/faster?
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Air could be cups (again), but we won’t know until we yank it apart. The procedure for checking on a leaking cup without disassembly is shooting the suspect injector with a laser thermometer so I’ll do that before we take everything off. It could also be the timing out of adjustment, a leaky injector, etc. CAT does specify in the service manual that our air symptom is acceptable, but it has to be coming from somewhere since the supply is clear

I have the 5 remans on hand and will find out about the 6th tomorrow. If it’s truly 2 months I may send one of my cores for a rebuild in FL and cancel the backorder. We’re going to replace the 5 and leave the 6th in place, run all the sync and overhead , and only redo the 6th cylinder when the injector comes in (or I get it rebuilt/tested)

im thankful and lucky to not have to pay cat for this, a friend is a diesel mechanic and has done many 3100 series (has all the tools, etc) so doing 5+1 doesn’t mean we’re doing the full job twice
 
Strecker25 said:
Air could be cups (again), but we won’t know until we yank it apart. The procedure for checking on a leaking cup without disassembly is shooting the suspect injector with a laser thermometer so I’ll do that before we take everything off. It could also be the timing out of adjustment, a leaky injector, etc. CAT does specify in the service manual that our air symptom is acceptable, but it has to be coming from somewhere since the supply is clear

I have the 5 remans on hand and will find out about the 6th tomorrow. If it’s truly 2 months I may send one of my cores for a rebuild in FL and cancel the backorder. We’re going to replace the 5 and leave the 6th in place, run all the sync and overhead , and only redo the 6th cylinder when the injector comes in (or I get it rebuilt/tested)

im thankful and lucky to not have to pay cat for this, a friend is a diesel mechanic and has done many 3100 series (has all the tools, etc) so doing 5+1 doesn’t mean we’re doing the full job twice
Click to expand...
At the injectors everything fuel is positive pressure so air can't ingest unless forced under higher pressure. That leaves combustion gasses. You can always route the gas ingested fuel into a closed container and put a CO2 tester like for a radiator to verify the gas is combustion residual but, really, there is no other source for those bubbles. Regardless, it's probably the seal(s) on the injector itself or a crack in the nose. If the cup seals were leaking you would find fuel or worse yet combustion gasses in the engine coolant. Pull the questionable one and look for soot tracing - possibly replacing the seals on that injector is all that is needed.
 
ttmott said:
At the injectors everything fuel is positive pressure so air can't ingest unless forced under higher pressure. That leaves combustion gasses. You can always route the gas ingested fuel into a closed container and put a CO2 tester like for a radiator to verify the gas is combustion residual but, really, there is no other source for those bubbles. Regardless, it's probably the seal(s) on the injector itself or a crack in the nose. If the cup seals were leaking you would find fuel or worse yet combustion gasses in the engine coolant. Pull the questionable one and look for soot tracing - possibly replacing the seals on that injector is all that is needed.
Click to expand...

that was our line of thinking as well plus, the engine runs super smooth. Maybe I’m mistaken but all the stories I read about a leaking cups usually accompanies hard starts and rough idle/running

disassembly should tell the full story. We shall see!
 
A friend of mine had couple of starter relays blowing on his 3116s. Is this a common issue on these engines?
 
Alex,

Older starter relays as those found on 1995 -1997 are pretty much bullet-proof in 19-1998 or Caterpillar changed the relays to small Bosch type relays and they don't seem to last long. Most owners carry several Bosch type relays on their boat as spares. I had the old style and ran my 3116's for 27 years and never had a relay fail.

Frank
 
Update on my knocking engine. Foley CAT came by yesterday and inspected it. Unfortunately, I wasn't there so the marina mechanic accompanied the CAT tech.

The diagnosis is that it is not a fuel issue and the fault lies with the injectors. He says sight glasses on the suction, pressure and return side of the fuel system show no bubbles or air in the system. Pressure was also correct..Now, onto the injector issue. Here's the part I don't understand. According to the CAT tech there is no way to isolate which injector is the problem and he recommends replacing all of them...Huh? He also says the seating cups need to be reamed. I find the latter difficult to believe given only 580 hrs on the engine, no air in the return fuel line and a blowby test well within normal limits.. As for not being able to isolate the bad injector, that doesn't pass the smell test..Can they not remove the injectors and test them on a bench?

It gets better. He also says the port engine, which runs smooth as butter, is running rough and needs the rack and injector heights adjusted. Funny thing, both were done at 510 hrs (now have 589 hrs). Went down the following day and the port engine was indeed running rough. It was running fins the day before the tech looked at it. Went down into the bilge to find the fuel priming selector knob in the wrong position...Turned it to the correct position and she again ran like a clock. Haven't touched the selector knob since changing fuel filters in October before laying her up. Only one to touch the engine since then is the CAT tech...

Am I right to be concerned? Just curious
 
Chris L said:
Update on my knocking engine. Foley CAT came by yesterday and inspected it. Unfortunately, I wasn't there so the marina mechanic accompanied the CAT tech.

The diagnosis is that it is not a fuel issue and the fault lies with the injectors. He says sight glasses on the suction, pressure and return side of the fuel system show no bubbles or air in the system. Pressure was also correct..Now, onto the injector issue. Here's the part I don't understand. According to the CAT tech there is no way to isolate which injector is the problem and he recommends replacing all of them...Huh? He also says the seating cups need to be reamed. I find the latter difficult to believe given only 580 hrs on the engine, no air in the return fuel line and a blowby test well within normal limits.. As for not being able to isolate the bad injector, that doesn't pass the smell test..Can they not remove the injectors and test them on a bench?

It gets better. He also says the port engine, which runs smooth as butter, is running rough and needs the rack and injector heights adjusted. Funny thing, both were done at 510 hrs (now have 589 hrs). Went down the following day and the port engine was indeed running rough. It was running fins the day before the tech looked at it. Went down into the bilge to find the fuel priming selector knob in the wrong position...Turned it to the correct position and she again ran like a clock. Haven't touched the selector knob since changing fuel filters in October before laying her up. Only one to touch the engine since then is the CAT tech...

Am I right to be concerned? Just curious
Click to expand...

id be concerned a bit about the selector valve and the recommendation there because it points to 3100 series inexperience

there are ways to isolate the bad injector but it’s not definitive. With the MUI’s you can’t do a cutout test and since you have to pull all the overhead to do just one of them and then adjust everything, it seems like a good idea to do all 6

in my case we know it’s cylinder 1 or 2 because we can use a stethoscope to hear it but that’s about as close as we can get

I don’t understand the recommendation to cut the cups if you have no air bubbles, that one does not pass the smell test for me at all
 
Strecker25 said:
id be concerned a bit about the selector valve and the recommendation there because it points to 3100 series inexperience

there are ways to isolate the bad injector but it’s not definitive. With the MUI’s you can’t do a cutout test and since you have to pull all the overhead to do just one of them and then adjust everything, it seems like a good idea to do all 6

in my case we know it’s cylinder 1 or 2 because we can use a stethoscope to hear it but that’s about as close as we can get

I don’t understand the recommendation to cut the cups if you have no air bubbles, that one does not pass the smell test for me at all
Click to expand...

Thanks for the advice. Supposedly, he's one of two techs who specialize in the 3116, and there's a big enough demand for 3116 techs given the amount of boats in Jersey that I believe it. Kind of a moot point as Foley is pretty much the only game in town here in N. Jersey..
 
Chris L said:
Update on my knocking engine. Foley CAT came by yesterday and inspected it. Unfortunately, I wasn't there so the marina mechanic accompanied the CAT tech.

The diagnosis is that it is not a fuel issue and the fault lies with the injectors. He says sight glasses on the suction, pressure and return side of the fuel system show no bubbles or air in the system. Pressure was also correct..Now, onto the injector issue. Here's the part I don't understand. According to the CAT tech there is no way to isolate which injector is the problem and he recommends replacing all of them...Huh? He also says the seating cups need to be reamed. I find the latter difficult to believe given only 580 hrs on the engine, no air in the return fuel line and a blowby test well within normal limits.. As for not being able to isolate the bad injector, that doesn't pass the smell test..Can they not remove the injectors and test them on a bench?

It gets better. He also says the port engine, which runs smooth as butter, is running rough and needs the rack and injector heights adjusted. Funny thing, both were done at 510 hrs (now have 589 hrs). Went down the following day and the port engine was indeed running rough. It was running fins the day before the tech looked at it. Went down into the bilge to find the fuel priming selector knob in the wrong position...Turned it to the correct position and she again ran like a clock. Haven't touched the selector knob since changing fuel filters in October before laying her up. Only one to touch the engine since then is the CAT tech...

Am I right to be concerned? Just curious
Click to expand...
Strecker25 said:
id be concerned a bit about the selector valve and the recommendation there because it points to 3100 series inexperience

there are ways to isolate the bad injector but it’s not definitive. With the MUI’s you can’t do a cutout test and since you have to pull all the overhead to do just one of them and then adjust everything, it seems like a good idea to do all 6

in my case we know it’s cylinder 1 or 2 because we can use a stethoscope to hear it but that’s about as close as we can get

I don’t understand the recommendation to cut the cups if you have no air bubbles, that one does not pass the smell test for me at all
Click to expand...
Reaming the injector cups is removing any soot tracing that may have accumulated not cutting metal.
I'm curious why replacing all the injectors. They can be tested. Injectors are hard to come by these days - new or rebuilt. I'd also get an oil analysis done with a request to look for fuel.
Have you had the five little plastic check valves changed in the injector pump? Those tend to gum up over time and cause idle instability do to varying fuel pressure.
 
ttmott said:
Reaming the injector cups is removing any soot tracing that may have accumulated not cutting metal.
I'm curious why replacing all the injectors. They can be tested. Injectors are hard to come by these days - new or rebuilt. I'd also get an oil analysis done with a request to look for fuel.
Have you had the five little plastic check valves changed in the injector pump? Those tend to gum up over time and cause idle instability do to varying fuel pressure.
Click to expand...


Thanks for the info. Oil analysis is done annually with the winter layup oil change. Last analysis was this past October (results showed no issues). First time starting her up since then was last week and that's when the knock started. Tech took oil samples, but likelihood of finding anything is slim as the engine was only run for five minutes since last October's oil change. Went from travel lift to slip. Haven't run her since for fear of damaging the engine. Figured I'd wait till CAT looks her over.

As for the check valves, haven't changed them. Quite honestly, wouldn't even know where to look up the parts..
 
Pgeee said:
Slowly coming to know the ins and outs of my 3116s. Just interested in the old pre walker air filter breather etc system I have. From what I know/see the blow by goes thru the breathers and loops back into the system via the air filters. I’m just surprised that that system is so open to the air, ie the last part prior to the air filter is just an exhaust like pipe which spews it’s gases through open air into the filter. Just seems a bit nuts to me but maybe someone at cat figured that out about 1998 which is why the walker system was introduced. Just intrigued ?
Click to expand...

I answered my unknowns above by researching more. Essentially the way diesels vented blowby in the 1990s and before was primitive. So CAT were evolving the process when mine were built. Seems it was common years ago to just vent into the open air,or in the case of a boat the ER. So the CAT system is comparatively state of the art 1996.
In the case of pre walker air separator cat 3116s like mine, I wonder how much of the general smell of the ER is due to that open part of the circuit where the blowby is hopping across open air to the air filter.
 
Pgeee said:
I answered my unknowns above by researching more. Essentially the way diesels vented blowby in the 1990s and before was primitive. So CAT were evolving the process when mine were built. Seems it was common years ago to just vent into the open air,or in the case of a boat the ER. So the CAT system is comparatively state of the art 1996.
In the case of pre walker air separator cat 3116s like mine, I wonder how much of the general smell of the ER is due to that open part of the circuit where the blowby is hopping across open air to the air filter.
Click to expand...
There shouldn't be any crankcase fumes in the engine room. There should be air flowing into that little filter not gasses out.
 
Have a question as to how to break in a rebuilt CAT 3116 engine.
Still a couple of months away from reinstalling the CAT 3116s and splashing the boat.
I know this subject is sometimes similar to the "what's the best engine oil" question, but here goes....

Here is an article about engine break in. Looking for input. Thanks.

Most manufacturers list procedures for break-ins in their operations manuals. Stick with these but also bear in mind the following routine. Remember, the first 50 hours of operation can significantly affect your diesel’s life expectancy.

Start the engine and let it idle for five minutes, making sure you’ve got cooling-water flow at the exhaust port and full shift control. Look around the engine room for problems and then, on returning to the helm, monitor your gauges. If engine sound changes or power falters, shut ‘er down and revisit the basics.

Continue to monitor your gauges while leaving the dock. Once you’re free of no-wake zones, slowly bring rpm up to cruising speed. Operate there for 15 minutes, then ease back to idle and shift into neutral for another five minutes. Now stop your engine and check the engine room again while posting a proper lookout, of course, and addressing any relevant navigational concerns.

Restart the engine and bring it up to cruise speed for an hour, then throttle back 200 rpm for an hour. Repeat this cycle and continue to vary throttle settings over the next 35 to engine 50 hours. Avoid prolonged operation at WOT and idling for more than 20 minutes, except in no-wake zones. The former will cause unnecessary wear while the latter will produce excessive soot buildup.
Click to expand...
 
I'd do a couple small cooling cycles and then use it normally to break it in under load. Most of the good trucking shops recommend breaking engines in with a loaded trailer.
 
SCFoster said:
Have a question as to how to break in a rebuilt CAT 3116 engine.
Still a couple of months away from reinstalling the CAT 3116s and splashing the boat.
I know this subject is sometimes similar to the "what's the best engine oil" question, but here goes....


Here is an article about engine break in. Looking for input. Thanks.
Click to expand...

I’ve never come across a CAT break in proceedure. But I would think standard practice would apply. No prolonged idle or WOT, and vary the RPM while at cruise. Monitor all fluids and temps, looking for a sudden change. Might burn a little oil at first till everything gets seated. Then follow the recommended schedule. The first big check is @250 hrs with resetting the valve lash and injector timing.
 
Thanks for the responses. Pretty much what I expected but never ever hurts to ask.
Spent a lot of time with aviation reciprocating and jet engines, but not an expert in marine engines.
As a funny aside, I got to pump birds through turbofan engines, to come up with specs for bird strikes. A fan blade will go through a 2” thick so called bullet proof window, when the fan section comes apart. Ask me how I know.

Thanks again.
 
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