Kohler 5ECD Not Running EC62, UU, UF

I remember reading that over there when I first bought my searay with the kohler and was starting troubleshooting. I’ve gotten more info here than from my kohler distributor.
100% agree. This thread and its corollary on the FB group are the reason my genset is running smoothly today.
 
Hey Everyone, Hope you're all staying safe and healthy. New to the group here and read all the great info, thanks! Anyway, I've been dealing with this demon Kohler 5E for the past several months. Hoping you all could lend some suggestions.

Generator would run for about 30-40 minutes with occasional surging and eventually die out. Things I've done thus far:
-New Impeller
-New Water Pump
-Flushed Heat Exchanger
-New Zinc Anode
-New Thermostat
-Coolant Flush
-New High Temp Cutoff Switch
-New Fuel/Water Separator

Now it's running for about an hour to an hour twenty minutes before it dies out. I have the older model 5E so there's no fancy error codes or display.

I'm going insane over here! Could it be this fuel pump you all are speaking of? Any insight would be greatly appreciated, thanks in advance!
 
Blow backwards through the thru-Hull valve. Mine was slightly clogged causing the exact same issue, except for about every 10-20 minutes.
 
Hey genset fanatics.

My 7.2ECD has largely been running flawlessly since I went through many days of troubleshooting and maintenance last fall with the support of this group. I was out yesterday and fired it up. It ran for about 30 minutes and then died with a UU. Went to restart and threw a UU. Opened up the bilge and went through several startup cycles (yes, removed the load before troubleshooting). The first few times I got an immediate UU. Then it starting to stutter a bit and then throw a UU. Finally it started, came close to dying, came back up, then down, and up, etc. Sounded like it wasn't getting fuel quite right, then a UU. Then one more try and it fired up and ran for the rest of the day, with load, until I turned it off.

I'm guessing somebody is going to say check the fuel pump, but both the electric fuel pump and the high pressure fuel pump are brand spanking new as of just a few months ago. No more than 20 hours of use on them. Impeller is brand new, sea strainer is clean, coolant wasn't overheating, SCR module is new, relay is new, fuses are new. And the kicker, of course, is that it got better and ran for a few hours. So far, I've yet to troubleshoot anything on this thing where the problem just goes away on its own. :)

Anybody have any thoughts to share. Yesterday, I was just trying to watch a little TV. I'd rather not run back into this problem when I really want/need the genset to be working.
 
fuel injector would be something but if it runs like you say then i hate to say it needs to act up again to diagnose.
fuel filter issue maybe something else to try.
 
UU or UF could both be caused by fuel starvation. could be something as simple as a restriction in the vent making vacuum in the tank, a bad filter or a plugged filter, it could be a defective pump or injector.

it could also be caused by a spark problem if one of the coils is getting hot and dropping out.

unfortunately if it only happens when it's hot that's when you're going to have to diagnose
 
UU or UF could both be caused by fuel starvation. could be something as simple as a restriction in the vent making vacuum in the tank, a bad filter or a plugged filter, it could be a defective pump or injector.

it could also be caused by a spark problem if one of the coils is getting hot and dropping out.

unfortunately if it only happens when it's hot that's when you're going to have to diagnose


also I can tell you if I shut mine off after it's been running it will not restart immediately because the pump vapor locks, it takes several start-stop attempts before it finally gets fuel. It's just a design issue with those.

Also check your sea-fire solenoid fuel shut off valves. if you have a loose connection it could intermittently drop and starve of fuel
 
Can you explain why you changed the high pressure fuel pump? Did you find any fuel pump corrosion similar to my original post? If so, then I would definitely suspect the fuel injector is gummed up if you didn't change it or clean it with your fuel pump swap. And you might as well throw 2 new spark plugs on it. That's easy - well should be depending on access.
 
Two questions, getting an immediate UU error, less than a few seconds elapse, might turn over once or twice, and it stops. Batteries were fully charged after an hours drive back to the dock. Earlier this year, I tried it and was able to push the run button and it cranked and ran. I shut it down, then restarted remotely, got a legit CO warning (hatch was open, wind was 5kts, right from the back corner of the boat), closed hatch, cranked again remotely, ran for 15-30 minutes under load.
Now though, immediate UU error. Focus on fuel first? I’m thinking bleed it, and see if there is any discoloration or slowness? Then check fuel pressure? If that’s good, I suspect it’s the ADC controller, or stay focused on the fuel pumps? If it’s bad, fuel pump replace...

Second, fuses were mentioned, i found the parts, but no way to get those by Saturday for testing, 1 10 amp 250V fast acting fuse, 2 10 amp 250v fuses, 3 15 amp, etc, are these available anywhere else, or do I have no choice but to get them online from ASAP, or other resources? I do have a friend in the small engine repair business, and he works on kholer generators, not marine though, might check there.
 
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Capture.JPG
Two questions, getting an immediate UU error, less than a few seconds elapse, might turn over once or twice, and it stops. Batteries were fully charged after an hours drive back to the dock. Earlier this year, I tried it and was able to push the run button and it cranked and ran. I shut it down, then restarted remotely, got a legit CO warning (hatch was open, wind was 5kts, right from the back corner of the boat), closed hatch, cranked again remotely, ran for 15-30 minutes under load.
Now though, immediate UU error. Focus on fuel first? I’m thinking bleed it, and see if there is any discoloration or slowness? Then check fuel pressure? If that’s good, I suspect it’s the ADC controller, or stay focused on the fuel pumps? If it’s bad, fuel pump replace...

Second, fuses were mentioned, i found the parts, but no way to get those by Saturday for testing, 1 10 amp 250V fast acting fuse, 2 10 amp 250v fuses, 3 15 amp, etc, are these available anywhere else, or do I have no choice but to get them online from ASAP, or other resources? I do have a friend in the small engine repair business, and he works on kholer generators, not marine though, might check there.
I ordered mine from colburnpower.com
 
Thanks, but my question was unclear. I’m asking if there are equivalent fuses I can purchase locally, quickly, so I can test on Saturday. Home Depot/hardware store/west marine/small generator repair store/etc. seems like a fuse is a fuse, but maybe not. I can find them everywhere online, even Amazon, but will not be here Saturday morning.
 
Can you explain why you changed the high pressure fuel pump? Did you find any fuel pump corrosion similar to my original post? If so, then I would definitely suspect the fuel injector is gummed up if you didn't change it or clean it with your fuel pump swap. And you might as well throw 2 new spark plugs on it. That's easy - well should be depending on access.
High pressure pump was a wreck. Impeller fin jammed in the outlet and salt everywhere. I'm a simplest solution guy and even though it required $$$, a new pump meant not having to clean it and continuously troubleshoot. I was in a bad place by the time I found that impeller fin. :D
 
also I can tell you if I shut mine off after it's been running it will not restart immediately because the pump vapor locks, it takes several start-stop attempts before it finally gets fuel. It's just a design issue with those.

Also check your sea-fire solenoid fuel shut off valves. if you have a loose connection it could intermittently drop and starve of fuel
Thanks for posting this! I've been having this behavior a ton and I didn't even think about vapor lock. 100% same behavior in mine. Cold start immediately, runs flawlessly for hours and then I'm out wanting to drift quietly and enjoy a beer so I cut engines and genset. An hour later, I'm ready to get underway again and the generator turns over for 2 or 3 seconds and fails with a UU. If I I start/stop a dozen times, I eventually get it started again although if the engines are running again, it takes way longer which I imagine is because the genset takes much longer to cool while the engines are hot. Sitting in my slip it recovers more quickly.
 
UU or UF could both be caused by fuel starvation. could be something as simple as a restriction in the vent making vacuum in the tank, a bad filter or a plugged filter, it could be a defective pump or injector.

it could also be caused by a spark problem if one of the coils is getting hot and dropping out.

unfortunately if it only happens when it's hot that's when you're going to have to diagnose
The failure scenario has only happened one more time. Not enough to troubleshoot. I was out for 4 days this week (spring break for the kids) and I had the vapor lock issue I replied separately about. But simply dying under load has only happened a couple times now. I might just have to live with it.
 
Two questions, getting an immediate UU error, less than a few seconds elapse, might turn over once or twice, and it stops. Batteries were fully charged after an hours drive back to the dock. Earlier this year, I tried it and was able to push the run button and it cranked and ran. I shut it down, then restarted remotely, got a legit CO warning (hatch was open, wind was 5kts, right from the back corner of the boat), closed hatch, cranked again remotely, ran for 15-30 minutes under load.
Now though, immediate UU error. Focus on fuel first? I’m thinking bleed it, and see if there is any discoloration or slowness? Then check fuel pressure? If that’s good, I suspect it’s the ADC controller, or stay focused on the fuel pumps? If it’s bad, fuel pump replace...

Second, fuses were mentioned, i found the parts, but no way to get those by Saturday for testing, 1 10 amp 250V fast acting fuse, 2 10 amp 250v fuses, 3 15 amp, etc, are these available anywhere else, or do I have no choice but to get them online from ASAP, or other resources? I do have a friend in the small engine repair business, and he works on kholer generators, not marine though, might check there.
UU is the most evil of all fault codes. Official description says you have to have voltage issues for 10 seconds but clearly not the case as I also see it on startup. It just means you have "issues." :)

CO sensor might be flakey since you mentioned that. I replaced mine during my troubleshooting insanity last year since I was getting a CO error when there was clearly no significant CO present (hatch open and nothing running prior). Officially, they are supposed to be replaced every year although that seems like overkill.

Fuses, SCR Module and GM28787 Relay all potential causes for UU. Flakey electrical stuff. I replaced all fuses and the module and the relay. I didn't have to replace the ADC controller itself which was nice as that is pricey. Once I got all the electrical stuff fixed, I had it starting and running well but had overheat issues and fuel flow issues. That led me to clean out the entire raw water cooling system. Salt, impeller fins likely stuck for years from prior owner. Replaced a few hoses, took the raw water pump apart and cleaned it up, new impeller and shaft sleeve (the yellow thing). I also replaced the pressure switch since I initially thought the overheat was due to coolant pressure when it actually was likely due to raw water flow issues.

I cursed a lot, but it runs as good as I can ask at this point. All day long. Still have the restart/vapor lock issue that Stray Current mentioned, but that appears to just be a design flaw that I have to live with.
 
UU is the most evil of all fault codes. Official description says you have to have voltage issues for 10 seconds but clearly not the case as I also see it on startup. It just means you have "issues." :)

CO sensor might be flakey since you mentioned that. I replaced mine during my troubleshooting insanity last year since I was getting a CO error when there was clearly no significant CO present (hatch open and nothing running prior). Officially, they are supposed to be replaced every year although that seems like overkill.

Fuses, SCR Module and GM28787 Relay all potential causes for UU. Flakey electrical stuff. I replaced all fuses and the module and the relay. I didn't have to replace the ADC controller itself which was nice as that is pricey. Once I got all the electrical stuff fixed, I had it starting and running well but had overheat issues and fuel flow issues. That led me to clean out the entire raw water cooling system. Salt, impeller fins likely stuck for years from prior owner. Replaced a few hoses, took the raw water pump apart and cleaned it up, new impeller and shaft sleeve (the yellow thing). I also replaced the pressure switch since I initially thought the overheat was due to coolant pressure when it actually was likely due to raw water flow issues.

I cursed a lot, but it runs as good as I can ask at this point. All day long. Still have the restart/vapor lock issue that Stray Current mentioned, but that appears to just be a design flaw that I have to live with.
Thank you for the help!
CO sensor on the Gen is supposed to be every other year, I thought I read that in the manual? My CO sensor happens to be new, it went out last year, (CO3, I think is the error code, or was it CO6?), regardless, CO sensor has worked flawlessly since it was replaced. I have the fuses, will start there. Then SCR and GM28787 relay.
 
Some quick repair tips - Kohler 5ECD: You should flush all marine generators after each use. Sea flush makes an awesome unit for this. The Kohler series catalytic units have had several design changes due to salt clogging the exit ports. Even with consistent flushing, you should inspect 1x year. Does your catalytic converter have a nipple at the top? If yes, this is the latest version and needs the least maintenance, salt wise. When removing to inspect, at replacement, use either anti-seize on the threads or use stainless bolts. Rinse all spilled, sprayed or dripped salt water asap. Avoid ethenol fuel at all opportunity. For easier access to the zinc, removing (4) cap nuts in the controller unit behind the ACD up makes that task quite simple. To get the HEX off "easier" at that hard to reach bolt, remove the (4) bolts on the catalyst (have gaskets ready and good time to inspect catalyst + discharge hose may need replacement) To get to the back bolt on the low pressure fuel pump, remove the (4) cap nuts inside the controller section and lift to side (when reinstalling controller unit, verify the plastic protector is in place on/around wires leading to the stator section.
 
Well, I'm back at troubleshooting the old Kohler again. :mad:

Last weekend, when I fired it up, the sound off the exhaust was notably different. My wife looked at me sideways; we both heard it. Operation is louder and there is a popping sound out the exhaust along with visibly darker gray smoke that would be typical. Running lean, maybe? Impeller is fine, raw water flow is solid. New electric and high pressure fuel pumps as of last year and I just installed a new injector today to see if it was clogged up, but no difference. Something's up with it. I have an O2 sensor for the exhaust, but I simply cannot figure out how I'm going to remove the existing one given its location on the back of the unit. I'm going to have to wear a tacky glove and hope I can wrench it off by hand and do it all totally blind. Barring that working, any other ideas on what might be going on.

 

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