Hard starting Onan

[Hippocampus]

On our new to us boat there’s an 11kw Onan. It’s real hard to start. Once going it works fine. Doesn’t skip nor does output vary. First thought it was an air leak as it will start after 2 minutes of priming and after 1 minute of priming if restarted within an hour of shutdown. So looked at all the fuel hoses and clamps. They’re fine. Then replaced the racor primary external fuel filter and the one inside the enclosure. Then the housing for the racor. At that point no joy so blew money on mechanics. So far 3 different mechanics have looked at it. Lift pump is fine. Weirdly it has anti siphon valves inside the enclosure. One seems to go from supply to return. They were replaced. At wits end. Can’t find an air leak. Don’t see any fuel on the diapers or on the engine. Starting to believe it’s not an air leak as it runs fine once you get it going.

Thoughts?

 

[Comodave]

Had a similar problem when I replaced the secondaries on our previous boat. I put some Napa filters in that the PO left aboard. American Diesel told me that the Napa filters were not good so I replaced them again and the problem went away. Check the filters and make sure they are properly installed. Also check all the fuel hoses for leaks. They can leak air in and not leak diesel out. So just because you don’t see diesel doesn’t mean the hose is good.

 

[rgano]

My Onan was only a 7.5 KW and had two glow plugs. Those plugs need to be in good shape. Mine also had a centrifugal switch which needed to function freely; if it is a bit sticky and corroded.... well, you get the picture.

 

[rgano]

One time I had an engine which would not start because the battery would not roll it over fast enough. It "sounded" like it was rolling ok, but just wasn't.

 

[BruceK]

Is it as I suspect, an EQD version? If not, are you holding down the "heat" function as you press "Start", they seem to like that.
If the "anti siphon" valves are an add on as I suspect, any idea why are they there and what they were to overcome? Something unusual added, and a problem which could be fuel related, may have a nexus.

 

[Lepke]

Not uncommon for filter housing to leak small amounts of air. Check gasket closely.

When cold, glow plugs may not be on long enough. My Onan started better when I put in a separate switch for the glow plugs.
You could have bad valves in the fuel pump. They function as check valves, allowing the fuel to move in one direction. When they start to fail or have debris stuck in them, the heat of a hot engine after shut down, expands the fuel, forcing it toward the tank. Or fuel return could have air in it and is being drawn into the injector pump on startup.
A 12v fuel pump would probably solve the problem. I added one to my Onan.

 

[Hippocampus]

All good thoughts. Thanks. Got the manual for this serial number. Check valves are stock. Replaced the racor housing and went up a size. Never had a diesel anything with check valves in it before. The bad fuel pump valves makes sense to me. Would expect trouble while running from a simple air leak but once running would expect the fuel pump valves to have the greatest effect at start up.
Lepke could you share the details of your adding a pump? Thanks

 

[High Wire]

How many hours on the unit? What percent of the 11Kw is the normal loading? When my Westerbeke would not start, and after going through fuel supply checks, it turned out to be low compression in all three cylinders.

 

[twistedtree]

After priming, it starts up as normal? What are the relative elevations of the genset and the actual fuel level in the tank?



One thing you could do to figure out if it's a fuel starvation issue would be to plumb in a temp fuel supply that is elevated above the engine. Then there would be no way for fuel to drain back to the tank. If it then starts normally, then you know you do indeed have a fuel drain-back issue. If the problem persists, then I think your fuel system is probably fine.


The other suspect area would be the glow plugs. The Onan EQ-somethingorother that I had a few boats ago did the whole glow-plug an start sequence automatically. Others may be like the NorthernLights generators where it's a manual process to run the glow plugs (override), then start. An electric meter on the glow plug terminals will confirm they are getting power, when, and for how long. And if you have a

clamp-on DC ammeter, you could confirm there is current flowing to each glow plug.

 

[rslifkin]

What model Onan is it? That would point to what engine it uses and possibly if there are any known starting quirks for that engine. As an example, the old J series Onan diesels were known for needing a ton of glow plug, a strong battery and still being a bit cranky about starting in cool weather.

 

[O C Diver]

You might try running the boat for a few hours without the generator. Assuming the generator is in the engine room, if the generator is over 100 degrees when you try to start it, the glow plugs may not be needed. So, if it starts right up or better than before, it's probably relative to the glow plugs.

A second thought would be to measure battery voltage at the battery cable connections to the engine when running the glow plugs and when starting. Low voltage affects glow plug temperature among other things.

Ted

 

[Nomad Willy]

Lepke wrote;
“When cold, glow plugs may not be on long enough. My Onan started better when I put in a separate switch for the glow plugs.”

Lep,
I had no idea there was any other way.


My G plugs are 15yrs old. Never cleaned them. The manual says no longer than 10 seconds. I almost always use 8 seconds. Took one out once just to see how dirty it was and found it to be as clean as one could expect. I’d call the glow plugs trouble free.

 

[Stout]

Onan MDKBL parts Manual

Hippo, I have a 2005 PDF version of the Onan MDKBL 9kw Parts Manual if it is helpful.

 

[Lepke]

Lepke could you share the details of your adding a pump? Thanks[/QUOTE
The electric pump is in the fuel line and replaces the original pump. I have a relay that turns on the pump whenever the fuel stop solenoid is active (allowing fuel flow). I added a on-off switch at the engine so I can run the pump for changing filters, bleeding. Much easier than pumping the handle on the original pump. I have electric pumps on 2 Detroits and both generators. The Detroit electrics only run when changing filters, when the engines are running, the gear pump pulls thru the electric w/o problems.
I made my glow plugs manually controlled because I didn't like excessive cranking in cold weather while waiting for the plugs to heat the air. It also works better because a large volume of air is heated in the intake manifold and the engine usually starts on the first revolution.

 

[Hippocampus]

Much preferred my NL to Onan. Manual was understandable and no peculiarities. Finding out how things are done varies by serial number within a model. Guess design engineers trying to justify their salaries. Check valves on this one seem to connect feed to return. Don’t understand why they are necessary. Oh well…..
NL had two separate switches as one would expect. Onan has one rocker switch. Push up get prime and glow. Wait 30 seconds get start. Push down get prime alone. Push down when running get stop. So can prime two ways by pushing switch either up or down. Priming for a minute by pushing down for 30 seconds then up for 30 seconds is very different then pushing up for two 30 second intervals. Been on the boat for the last week messing with watermaker, Espar and new electronics. Finally home to decompress for a day before leaving for Virginia. When back will try both ways of starting. From boating and RV friends find out unlike the NL where you wanted to avoid more than 3 start attempts or long start attempts (needed to remove cooling impeller and drain then) with the Onan that’s not the same concern. So I’ll try using the up push on the rocker switch for 30 seconds a couple of times without the down prime before troubleshooting further when I’m back. The NL required priming on a separate switch before start.

 

[O C Diver]

One more thing:

Does your generator have a lift muffler? Extended cranking can fill it with water and create engine back pressure (among other problems). If it has a drain (many do for winterizing), open it until it starts. If it starts easily, that may be part of the problem.

Ted

 

[ranger58sb]

FWIW...

Our new-to-us genset is a 2006 21.5 kW Onan MDKBE, and since we're approaching winterizing time, I spent yesterday trolling for documentation. The Cummins QuickServe Online site presented 5 useful manuals for our serial number: Install, Operator, Parts, Accessories, and one about Siphon Breaks. Each manual covers several variations (MDKAV/W/Z, MDKBD/E/F/G). Easy PDF downloads.

Another FWIW, our Start/Stop sequence is controlled by two separate rockers. One is just a single throw ON/OFF.

The other is dual throw Start(Run) at the top and Stop st the bottom, with flashing LEDs to indicate the warm-up period and when to let go of the rocker (genset is now running properly). IOW, holding Start(Run) eventually starts the genset, after about 30 seconds or so of light show.

-Chris

 

[Hippocampus]

Yup thanks already got the manual for our serial number.

Genset at same level as fuel tanks. Actually given just filled tanks fuel level is higher than genset.

The lift muffler issue was why I had to drain the NL if 3 start attempts didn’t work. With this one there’s a fancy Dan muffler system so neither the main propulsion engine nor the genset exhaust exit above the water line. Both drain when engine is off. Been told no way cooling water can backfill into the engines.

 

[twistedtree]

If your fuel tank level is above the genset then it's hard to understand how there could be any drain-back issue in the fuel system.


I think a good next step is to verify the glow plugs are working, first checking for voltage, then confirming there is current flow to each. I have probably 1/2 dozen Kubota-powered pieces of equipment and they definitely need their glow plugs to start in any reasonable fashion. But with proper pre-heat, they always kick right off, even in sub-zero weather. The problem could be as simple as a blown fuse or a failed relay.

 

[Hippocampus]

Good thoughts.

 

[ranger58sb]

Another FWIW, our Start/Stop sequence is controlled by two separate rockers. One is just a single throw ON/OFF.

The other is dual throw Start(Run) at the top and Stop st the bottom, with flashing LEDs to indicate the warm-up period and when to let go of the rocker (genset is now running properly). IOW, holding Start(Run) eventually starts the genset, after about 30 seconds or so of light show.

I did that from memory, but then I was on the boat today so...

Our two-way rocker is marked Start/Preheat on top, and Stop/Prime at the bottom. Two lighted areas in the actuator, green high (marked Run), yellow low (marked Preheat Status).

Holding Start/Preheat causes the yellow light to flash... until the engine starts and eventually reaches Run status... when the green light comes on.

-Chris

 

[SteveK]

WAG
What about the shut down, could it stay stuck in the kill engine position and clear after a few revelations.

 

[Hippocampus]

Thanks all. Learned a lot. Pressed start (upper rocker) without pressing prime (down rocker) for 15 seconds. Onan started. Believe whole thing was I didn’t understand manual and multiple wrenches didn’t either. Language in manual obtuse. Prior owner, brokers not helpful. A friend clued me in to correct starting procedure over the phone. Totally embarrassed that a supposedly smart guy like me didn’t figure it out by myself earlier. Of course changing all filters( they were very dirty) and the filter house for the primary as well as tightening all connections (some of the hose clamps were so loose as you could spin them) might have been the trouble. But have joy. Thing works. Work done on it was worthwhile and now know this machine. Move on to next chapter of the saga of “new to me”.

 

[SteveK]

Totally embarrassed that a supposedly smart guy like me didn’t figure it out by myself earlier
There is a lesson there. Men take things literally. So when a smart guy like you asks for help and tells us he has done everything right, no one thinks to ask the obvious question, in this case list your starting procedure.
Glad you found out how to start it, maybe another person can learn from it

 

[C lectric]

^^^^^^^^^^When cold, glow plugs may not be on long enough. My Onan started better when I put in a separate switch for the glow plugs.^^^^^^^^^

If you do install a switch to control the heaters use a MOM ON switch which will turn off when released without you having to remember.
Get distracted and you will forget and burn the heaters.
Different problem but I did that and the repairs cost me a few hundred $. THe repair included a MOM ON sw.

 

[Gordon495]

Probably nothing but check your fuel rack linkage from the stop solenoid to make sure it's fully opened when energized. Remember that when energized the coil will hold back the actuator and allow the fuel to flow and then stops it when the power is disconnected and the coil releases. If it's slightly restricted, going only partially open, it could cause issues. And go even further, disconnect the linkage from the stop solenoid and then see if you can open the throttle further, maybe it was never adjusted properly. Like I said it's probably nothing but start with the basics. Why not pull an injector line off and attach a clear plastic tube to the line and run it into a container and see how the flow is, not much comes out but you'll see if it's consistent. How many hours are on the genset and what maintenance has been done to it ? Diesels are quite simple and to run only require a fuel source, lift pump, injector pump, injectors, glow plugs if equipped, air source and compression and a fuel rack to stop it. It's also possible that the injectors are showing signs of wear and not giving you proper atomization. It sure sounds like a fuel issue but is there a chance it's a compression issue ?? it sounds like it has the makings of it but I'm sure you've already looked at that. Check your air intakes to make sure your supply is good ( air filter ) If I can think of anything else I'll get back to you. Good luck

 

[Comodave]

Thanks all. Learned a lot. Pressed start (upper rocker) without pressing prime (down rocker) for 15 seconds. Onan started. Believe whole thing was I didn’t understand manual and multiple wrenches didn’t either. Language in manual obtuse. Prior owner, brokers not helpful. A friend clued me in to correct starting procedure over the phone. Totally embarrassed that a supposedly smart guy like me didn’t figure it out by myself earlier. Of course changing all filters( they were very dirty) and the filter house for the primary as well as tightening all connections (some of the hose clamps were so loose as you could spin them) might have been the trouble. But have joy. Thing works. Work done on it was worthwhile and now know this machine. Move on to next chapter of the saga of “new to me”.

Don’t beat yourself up too much, we all have things like this happen to us. I usually jump to the worst scenario and assume that the problem is serious because that is the way you usually think, the worst has happened…. But after a while and I calm down I can usually start to think straight and figure it out, sometimes with a lot of help from TF members.

 

[Gordon495]

Guess I should have read All the posts before throwing in my 2 bits haha
Glad you resolved your issue

 

[Hippocampus]

More to the story

In transit from RI to VA. Initially ran generator to have Seakeeper. Left Tuesday late morning. Today around 11a Seakeeper gave message low voltage. Checked generator it stoped. Restarted it without trouble. After an hour stopped again. Repeat sequence after 1/2 h. So no genset. No Seakeeper. Short handed. Can’t drive boat and mess with genset. Will go Delaware, C&D chessie instead of outside. Adds 56 nm but safer in now unstabilized boat. Dislike Onan.

 

[rslifkin]

There are generally only a few things that'll cause generator shutdowns like that. Either fuel supply, overheating, high exhaust temp, or low oil pressure. So it shouldn't be too hard to troubleshoot when you get a chance.



As far as running unstabilized, don't forget, the Seakeeper doesn't enhance the boat's capabilities, just comfort. So you can still run without it just fine on the outside as long as you can tolerate the motion.