Kohler 7.5EKD Vapor-locks

[insfnds]

We have a 2011 390DA with a Kohler 7.5kw genset with sound shield that vapor locks every time I use it. It runs great initially, but if I shut it off for more than a few minutes, it wont restart for 4 to 6 hours. The dealer has been trying to resolve this for three years now with no resolution in sight.

If the sound shield is removed, the genset still struggles to restart but eventually does. But the genset is so darn loud that this is not a valid solution. (Heck, the genset is too loud with the sound shield on.)

The dealer tells me that this is a common problem with these gensets in warmer climates but I haven't found any one else complaining about this on the 'net.

Anyone else ever have this issue or hear of anyone with this issue? Thanks!

 

[Sal A]

Just want to follow this. I have the same issue with my unit a bit older then your 2011. Mine runs fine for about an hour then shuts down if I bleed the air from the coolant system it will run all day. If I shut it down and restart it a day later it runs for an hour then shuts down. I have to bleed it and we are all set to run for the day. I pressure tested the coolant system no leaks. Today I changed the radiator cap we shall see.

 

[Sal A]

For what it's worth I replace the heat exchanger cap (13 psi radiator cap) it ran for 6 days for about 2 to 3 hours a day and never vapor locked.

 

[insfnds]

Sal A, thanks for the response. Was yours vapor-locking before you changed the cap? The issue with mine is it will run and run and run, but if I shut it off, it wont restart for 4 to 6 hours.

My dealer has been in contact with Sea Ray and Kohler again as I'm demanding they replace the genset since they can't fix it. Kohler is balking, blaming Sea Ray for not installing properly or some other BS. They are saying the heat from the engines for causing the vapor-lock which would make sense except that I can get the genset to vapor-lock without running the engines.

 

[Gary Hill]

Yes, Sal and Insfnds, you guys are talking two different problems. Insfnds, heat soak is part of what you are experiencing and causing the vapor lock at least partially. Our Kohler 7.5 ec does the same thing up here in Michigan if it is not shut down correctly. The first thing you need to do when you want to shut down is to turn the Gen breakers off and then let the gen run for at least five minuets. If you don't run your blowers while running the gen turn them on while in this cool down mode. What you are trying to do here is cool the engine down. After the gen is running unloaded for five minutes or more shut it off and leave the blowers going for another five minutes or more.

Heat soak is common in these and other types of combustion engines. It refers to the engine block and the rest of the parts soaking up the heat from a hot engine and surrounding area. If the engine is hot enough it will vaporize gas in the line causing the vapor lock. Cool that baby down slowly and efficiently and your problems may go away. It is hotter down there but I'm betting a long cool down period will help you.

Good Luck.

 

[insfnds]

I can see how running the genset with no-load would help it cool down, provided it would idle down as well, but not so much since it continues to run at 3600rpm. I will give this a try though. Blowers are always running if any of the engines, including genset, are running.

 

[Sal A]

Yes mine would shut down while running. After I replaced the cap it ran perfect. I do run it with no load to cool it down like Gary hill does.

 

[Gary Hill]

I can see how running the genset with no-load would help it cool down, provided it would idle down as well, but not so much since it continues to run at 3600rpm. I will give this a try though. Blowers are always running if any of the engines, including genset, are running.

Yup give it a try its at least cheap. The engine running unloaded will run cooler and remember the gen portion crests heat when loaded up as well.

I hope it works for you.

 

[insfnds]

Gary, you were right about the cooling off period, the manual says to let it run for two minutes unloaded before shutting down. It would drop in temp anywhere from 5° to 9°F. Unfortunately, this did not solve my issue.

Sea Ray sent a Kohler 'expert' to look at my genset. He found that the high pressure fuel pump wasn't holding pressure in the fuel rail when the genset was shut down which was allowing it to vapor-lock. After replacing the fuel pump, the genset would restart every time when hot.