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Kohler Generators, Fuel Pumps, and Tanks
I learned about all of the above this week and thought that I’d take the opportunity to share some of my new found knowledge.
For background, note that this is the same bus and generator that had the well documented fuel pump failure several years ago when it belonged to Mango Mike, which appears at: http://prevoman.com/Pages/Gen%20Fuel%20Pump/page1.html
Mike’s article talked about a fuel pump failure and how he successfully substituted a common automotive pump as a temporary fix. I bought the bus in 2010 and almost from the start I had random generator problems due to fuel starvation and air ingestion. Hard starts were the norm, especially after several days of sitting. Sometimes, during the summer and under heavy loads, the generator would brown out (slow down) and just stop. In these cases, it required that I perform the Kohler fuel bleed procedure (simple but irritating) to get the air out of the lines. I also noted that the problem was often worse when the main fuel tank was below 1/2 full.
This week, finding ourselves in Eugene, Oregon, we checked into Coach Pro, a local repair shop that specializes in Prevost. Nearly everybody there has previously worked at Marathon and their knowledge and experience is incredible.
After I told them of Mango Mikes story with the temporary pump and subsequent replacement with a new, Kohler (Yanmar) pump, and a description of the symptoms (air in the lines), it was decided that it might be a good idea to check the fuel tank distribution manifold for suction leaks, etc.. This is fairly simple and accessible on a Liberty since the access door is readily available on the right side in the OTR condensor compartment.
An initial examination of the manifold showed no leaks and everything looked good. It was decided to put a check valve in the line at the tank, just to see what would happen. We ran the generator that night and it still exhibited the same problems, having numerous stutters and one brown-out during the course of the evening.
The next day, we opted to pull the manifold plate off of the tank to have a look. The manifold is a metal plate about 8 inches square that is attached to the top of the poly fuel tank. On the bottom side of the manifold plate, rubber hoses hang down to pickup the fuel. These hoses have brass T pipe fittings on them to weigh them down to the tank bottom. One very interesting note was that the generator down tube was notably shorter than the engine tube. In fact, the Prevost tech (Kevin) told me that this is intentional so that the generator may not deplete the engine fuel supply. I recall that the quote was that the thank was 24″ deep and that the generator pickup tube went down 16 to 18″. This clearly suggests that below 1/3 of a tank that generator use is iffy at best!
All of the down tubes and the manifold checked out OK. We were hoping to find the answer to this now chronic problem but to no avail. The manifold was reinstalled and we moved our attention back to the generator compartment. A fuel pressure gauge was placed on the supply pump output and it measured barely 2psi. We disconnected the line and let the pump run into a bucket and noted that barely a trickle would flow. At this point, we decided to try a new pump. Not having a Yanmar pump at hand, we elected to try something from NAPA auto parts and Facet Cube pump was selected. See: http://www.facet-purolator.com/cube-fuel-pumps.php Now this is an odd looking pump! In fact, it doesn’t look like a pump at all, but rather a cube, as the name says. Apparently, it’s electronic meaning that it’s “brushless”, but I could not learn much more about it. We chose the one rated from 3.5 to 7 psi (35 Gal/hr) based on the advice of a generator specialist. Apparently, it’s not good to use a higher capacity pump in this application.
In the end, the new pump was an easy fit, bolted right to the engine, and performed flawlessly. The fuel pressure from the new pump was about 4.5 PSI and the “bucket” flow was impressive! After running the generator for many hours now, it is behaving like it’s had a heart transplant. The generator is now smooth, starts quickly, and puts out full power under the biggest loads I can throw at it.
Why didn’t we try the fuel pump first? Well, it’s because the symptoms weren’t 100% consistent with a fuel pump failure, and, I was operating under the knowledge that the existing pump had fewer than 500 hours on it since Mike’s replacement. Also, the air in the fuel line was perplexing, suggesting an upstream suction leak. Its behavior on lower tank levels (below 1/2 tank) was likely due to gravity and the placement of the pump relative to the height of the fuel.
It was a lot of work to fix an otherwise simple problem, but I’m nonetheless happy. This coach is never happier than when it’s running on the generator and all 4 Cruise Air’s are humming along nicely.
Finally, I’d like to give a big hat’s off to the Coach Pro crew in Eugene. Their dedication to finding a solution was tireless and they really bent over backwards to make sure everything was right before I left their shop. Two thumb’s up, I highly recommend these guys!
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17 Replies
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I cannot remember the details, but I recall somewhere, maybe on POG, that the Kohler (Yanmar) fuel pump was a potential problem. At around the time that was discussed some folks mentioned they had to replace one.
A short time after that discussion our generator had trouble maintaining RPM under relatively light load, and when a Cruiseair cycled on the generator bogged down and stopped running. After a few minutes of checking and not seeing anything obvious I restarted it and it ran fine. But rather than risk a problem I ordered a new fuel pump and installed it. I never had a problem after that.
They are pricey and if I remember the replacement pump was about $360. I still carry a spare, but since the last problem about 6 or 7 years ago I have never had any issues.
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I am paranoid about my Kohler generator,I have had a total failure once and one shutdown.I have found Kohler to be impossible to deal with as we’ll as their distributor/service center.I wish that Liberty used Power Tech as they have more service centers.Since I am concerned about the gen I also carry a spare fuel pump.
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My 98 Liberty has a power tech runs great, I wonder what year they switch over?
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Fred,
I remember that fuel pump vividly, as Jdub and I helped Mango rig
up the automotive pump and it worked great. It was a cold windy rainy
night in Albuquerque at the Balloon Festival and we all looked like
drowned rats, especially Jdub. Mango did the right thing by putting a
new pump back on, to bad it didn’t last, that sucks. -
What Tom is not revealing is while he, Mango, and JDUB were working on the problem in the cold rain Tom’s job was to hold the umbrella while Mango and JDUB did the installation of the temporary fuel pump.
Upon seeing JDUB’s butt crack Tom was unable to resist directing the flow of water coming off the umbrella right at the aforementioned butt crack. Hence for a while after that incident Tom was called “Crackman” by JDUB.
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Ya had to be there!!!
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With that description from Jon,I guess we all were “there” at least in conjured up images…whew
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You are right about images. Now I can’t get it out of my mind.
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In an effort to get the discussion away from the crack images I will add that I have had very similar problems to what flloyd described with my Kohler generator over the years. As recently as this past weekend it would not start after not being used during its previous excursion and after I had run the fuel well below the 1/3 point before refueling. I am now starting to wonder if the source of my problem is the point of fuel pick-up in the tank as the folks as Coach Pro deduced. My solution, which has worked for over two years now, and came after what I felt was the premature 2nd replacement of the fuel pump, was to install an off/on switch in place of the momentary switch used to prime the fuel pump. In the occasional instances where my generator will not start I merely flip the prime switch and then start the unit after I can hear that the pump is well primed. Typically I will leave it in this mode a few hours until enough fuel has run through the line to find all the air pockets. The only risk I see is forgetting to flip the switch off were I to shut down the generator from inside the coach and overlook turning the primer off.
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I had a Kubota powered generator on our first Liberty.
If the generator had been run within the previous day or two it started OK, but longer than that it needed to be primed. I just brought 12 volts to the fuel pump and listened to it prime. I never bothered to check out why it lost its prime.
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on the topic go generators but not fuel pumps I know that power tec suggest hoses be replaced every 2 years I believe. Has anyone replaced the hoses and what interval is reasonable?
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On my 87 when it was about 15 years old all hoses looked good. but when one started leaking I realized they were all in very bad shape. The blue hoses on the engine were OK, but other hoses including the generator were margtinal at best. I replaced them all.
My 97 coach got them changed at about 10 years I think. I don’t remember changing the generator hoses at that time. It was a Kohler instead of a Universal and I think better quality hoses were used. The ones installed in the Webasto system were in bad shape and they got replaced.
Replacement hoses were cheap. We have an O’Reilly warehouse near us and even if I couldn’t get the exact hose I could get one of the correct diameter with the type of bends I needed and cut it to length. If in doubt, change it out.
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I replaced all fuel lines hoses and thermostat I put about 50 hours a week on gen works great power tech
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So I finally make time to come read this Krakman stuff (spelling wasn’t Jon’s strength in school) and they almost got it right. While I was performing as McGuyver-esk on the fly fix of the errant fuel pump, my buddies jack with me earning them retribution to no end. And I’m sure they won’t mention all the ways I got even.
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Since you brought it up, rather than dancing around the edges why don’t you tell our 600 visitors today the whole story from your perspective. I assume Tom (Krakman) will suggest some modifications if you don’t get it right.
The way I heard it he aimed copious amounts of cold Albuqueque rain water down a plumbers crack from the umbrella he was holding.
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