Kohler Generator Dieseling!

[ClydesdaleKevin]

Sent: 10/07/2007 

I wasn't sure if this was an electrical problem, or mechanical, or both, so I posted it here:

On the way up to Wisconsin from Georgia, I shut off the genny once from the dashboard remote switch...it works to shut it off, and the hour meter still works in the dash, but the switch doesn't START the genny from the dash...you have to start it from the genny compartment...its SUPPOSED to start it from the dash, but the wiring is bumbled somewhere along the way...but that's not the reason for this post...that is something I can troubleshoot and repair myself.  Anyhow, when I shut it off from the dash that one time, it did indeed shut off, but I had to hold the button in or else the genny would diesel for a while, huffing and puffing, and if I released the switch too soon, it would start back up all by itself.

So, I figured it was probably a result of the poor wiring from dash to genny...but now, and it didn't do it before, it diesels even when I shut it off from the switch which is ON the genny!

The genny still runs fine and smooth, puts out the same number of amps and watts and volts (its a 6800 watt genny), and it starts right up as easily as before from the genny switch on the genny...but now it is still dieseling when I shut it off, and even from the switch on the genny, I have to hold it in for up to a whole minute while it diesels and chugs and finally shuts down...if I don't, it starts right back up sometimes, and other times it just keeps chugging and dieseling until it finally shuts itself down after several minutes.

Any idea what could cause this?  Everything else on the genny is working perfectly.

Thanks!

Kev

[Henry]

Sent: 10/07/2007

My guess would be carbon buildup and/or carb leaking gas into the intake.

Henry

[DanD2Soon]

Sent: 10/07/2007

Kev - try just putting in a new sparkplug - DanD

[ontheroadagain]

Sent: 10/07/2007

Most small engines ground the ignition.  To shut it down, check the ground connection to the switches.  Mine did the same thing.  The ground wire had loosend up just enough to make a poor conection.

[Slantsixness]

Sent: 10/07/2007

Kev-
If a gas engine is dieseling, there usually are one of two causes:

1. Ignition shut off switch or in your case, a relay not grounded, or not activating.
2. Overheating. Check the air inlet to the generator fan for an obstruction(s) it could just be overheating to the point of dieseling when shut off, which is common if there is carbon buildup. these generators basically will run the carb out of fuel if this condition exists. Even with the electric fuel pump having been shut off when you shut it down, the average Genny motor can run  at low (unloaded) idle for 10 minutes or so off justr the fuel in the carb float bowl.

And check the fan/blower for ample airflow when running. maybe something came loose, or detached ("it happens"). If it's dieseling and you're trying to shut it down, the engine will probably only be turning at 60rpm or less, so the fan probably won't move much air at 60rpm... I think the industry standard is 1000rpm continuous and 1200 at peak draw. for your average RV genny... anyway, that spec is on the genny label....

Check the wiring. it's possible that the relay is going bad / bad / went bad for the remote start: which is the same relay used for shut down from either position.
A bad ground to the relay, or anywhere in the genny compartment can cause shutdown/startup not to work properly, or at all.

Tom

[ClydesdaleKevin]

Sent: 10/07/2007

Thanks guys!  I have to change the oil and filter soon, so I'll change the spark plugs while I'm at it.  I'm also going to check ALL the wiring, from dash to genny, as soon as I have some time, and its either cool enough or not raining...lol!  We've has some wicked weather up here the last few days.

I did check the airflow and the fan screen...all clear, and PLENTY of forced air coming out the bottom when its running.

I'll let you guys know!

Kev

[ClydesdaleKevin]

Sent: 10/09/2007

Replaced the spark plugs, and the genny doesn't diesel anymore!  Yay!  The bad news is that when I was replacing the oil filter, the 1/2" pipe that threads into the oil filter body came out with the oil filter, and when I tried to get it out, I stripped its threads.  Now, it is indeed 1/2" pipe, but it isn't pipe threads...its the same threads used on 1/2" brass flare fittings...oi vey!  I couldn't find anything that would work, so I bought a male/male brass flare fitting, drilled it our so it wouldn't restrict oil flow, ground off the ends and the flats in its center, and it actually works!  When we get to Texas, I'm going to order the correct part from Kohler, but unfortunately, just the little pipe isn't available...I'll have to buy the whole oil filter assembly...arggghhhh!

Kev

[Slantsixness]

Sent: 10/09/2007

Kev,

Welcome back! (ok... "welcome back online"... but still...!)
That fitting is the same on a bunch of old cars (60's and 70's Ford six cylinder motors, also there is a steel replacement in mid 70's). Rather than buying a whole new oil filter housing, just stop by a junkyard or even a NAPA on your way south. And even better still, I think I have one in the lucky box... let me check and I'll send it to ya!

Tom

[ClydesdaleKevin]

Sent: 11/09/2007

Hey Tom!

The one NAPA I stopped at had everything BUT the one fitting I needed.  I told them I didn't even care if it was longer, since I could cut it down on my metal chop saw, but the closest thing they had was pipe-threaded. 

Kev

[ClydesdaleKevin]

Sent: 20/09/2007

OK...now the genny is running worse than ever.  When we drove down from Wisconsin to Salado, Texas, we left the genny off to conserve gas, and since it wasn't too hot on the way down for the trip (we drove mostly at night) that was all good.  The problem came when I fired up the genny at the campsite for the Salado mini renaissance faire.  At first she fired right up, and a shutdown and restart showed it wasn't dieseling anymore.  It was running great!  Then about 24 hours later, she started laboring like she was under a heavy load...then stalled.  I went to the compartment, unplugged from the genny to make sure there was no load at all on it, and tried to restart her....and MAN did the genny seem hot!  No spark at first.  I let her cool down for a few hours, and she finally restarted reluctantly.  But she was still laboring like under a heavy load...oil pressure was perfect, oil level perfect, but something is making it labor.  If I turned on the air, she stalls, and diesels until she finally goes still.  If I keep the air off, she'll run for an hour or so, laboring, and then stall, dieseling. 

Now, my temp fix of the oil filter might be causing the overheating...the bore of the fitting I used, even though I drilled it out as large as I dared, is smaller than the bore of the original oil fitting, so perhaps the oil flow is restricted, and perhaps there is a safety shutoff switch that shuts down the genny when it reaches a certain temp.

I haven't pulled the new spark plugs yet to see if they are fouled, but I'm guessing they are...it seems like they are, what with the dieseling and the loss of spark and power.

I know it isn't a gas issue, since the pump flows fine...and the filter isn't blocked. 

Any ideas?  Could it need new points, or a timing adjustment or something?  Do the symptoms sound familiar to anyone?

Kev

[ClydesdaleKevin]

Okay...heres the bottom line on our 1977 Kohler generator, and its deiseling problem.

In 1977, 76 when it was made, this engine was made for leaded gas.  Leading raised octane VERY much more than the current numbers, but now its all unleaded.

When I rebuilt the carb on the genny I didn't know much about all this, so I erred on the side of caution and ran it rich to keep the heads cooler...old VW trick.

Good thing I did!  Its what you SHOULD do when running a leaded engine unleaded.

But, now it deisels because of the extra carbon...the carbon stays hot, the engine manifold pressure still draws in gas and air, and it deisels.

The solution?

A fuel shutoff solonoid valve!

For now, if I go to the generator compartment and push the shutoff button and then turn the existant manual fuel shutoff valve off at the same time, as soon as the valve is close, the genny shuts down and the diesleing quits.

Very soon I'll add a solonoid that shuts off the fuel supply as soon as the electric fuel pump shuts off, which is essentially all the button does.  Then I can shut it off FROM the dash.

Kev

[DanielTBolger]

U might try a colder spark plug in it  or make sure the carb is close off to idle.