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Old 27-04-2015, 15:26   #1
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Onan diesel genset inscrutable problem

I have an Onan genset in my lazarette. Its the MDK 7/9 kW. It runs fine except for an overheating issue (I have heard they all tend to run hot, and solving it with an auxiliary fan)
The genset stops and I get the lack of fuel error message (3 blinks) . It stops, instantly, when I step in a certain spot on the floor in the aft head. This spot is on the other side of a bulkhead about 2 feet away from the generator. There are no wires or anything under the floor that could be moved or squeezed by my stepping on it. The hull is aluminum and plenty big, so its not a question of the boat tilting to one side or the other. I first thought somehow the fuel line which runs three feet away was being squeezed somehow. I replaced the entire fuel line. No help. I tried running the genset from a jerry can with the same results.

I have only 140 hours on the genset over the past couple of years for this very reason.
Any ideas other than consulting a shaman?
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Old 27-04-2015, 16:15   #2
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Re: Onan diesel genset inscrutable problem

I have the same unit.
Only time it has stopped is when water flow was low or not at all.
The heat exchanger had about 3 impellers worth of bits in it stopping good flow through it.
I took the end off and cleaned them out as well as bits in the hose after the water pump.

The other issue causing it to stop was loose cable connections of the power out cables,it detected a fault and shut down.




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Old 27-04-2015, 17:59   #3
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Re: Onan diesel genset inscrutable problem

I have a MDL3.
Some things I have seen...
In still water, if your salt water intake is too close to the exhaust, a small area of water can become heated and sends too warm water to your heat exchanger. Or could the intake be picking up exhaust water from your mains? I saw another boater with his incoming pickup directly behind his keel coolers. Also, your temperature sensor can fail. Verify your fuel pump is supplying enough pressure to the injector pump. Verify your salt water pump is moving enough water.
In marine climates, cleaning all the contacts, inside and outside the control box sometimes helps.
Error codes are not always correct. It may be a problem further down the line that triggers the low fuel. If you know wiring, bypass whatever is activating the kill circuit. Keep an eye on the gauges.
If all else fails, you could do magic tricks by that patch of aluminum.
Lepke.
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Old 03-05-2015, 07:40   #4
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Re: Onan diesel genset inscrutable problem

dohenyboy

I don't have an Onan and have a few thoughts of what I would do. Take it as my 2 cents worth.

1. Is this genset in a sound shield? If yes, try running without sound shield. If the problem does not occur, then heat is the problem so a fan will help. Even the other big makers require a fan for cooling for the sound shield.

2. Use a IR temperature gun to take reading of sea water at sea cock vs temp at the raw water pump. If the difference is a few degree, there is some blockage in the raw water. A very article written by Dockhead

ref: Generator -- Temperature Monitoring

3. A check on exhaust elbow for carbon deposits which may restrict flow. Enough to look good without load and overheat under load or after warm up.

4. There could be wiring loose causing the electronic module to shut down.
- try remove the remote panel, if any and start genset from the genset panel
- check to see if the fuel sensor is normally open or normally closed. A multimeter is needed here. See if you remove and manually close/open will replicate the symptoms. Test the sensors too. Maybe a faulty fuel sensor.

I don't understand what you mean when you said "The genset stops and I get the lack of fuel error message (3 blinks) . It stops, instantly, when I step in a certain spot on the floor in the aft head." Are you saying the errors goes away you can run the genset again, and the error comes after some time again?

5. Try installing an 12v electrical fuel pump. May help if genset if above the fuel tank.

Keep us posted on your progress.

Eric
genset is Entec Farymann 1 cylinder 3,600 rpm 4kva 1,241 hours
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Old 03-05-2015, 07:51   #5
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Re: Onan diesel genset inscrutable problem

Quote:
Originally Posted by dohenyboy View Post
I have an Onan genset in my lazarette. ... It stops, instantly, when I step in a certain spot on the floor in the aft head. ...
Any ideas other than consulting a shaman?
Ah... Put a large "NO STEP" placard on the spot and stay away from it?
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Old 03-05-2015, 19:48   #6
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Re: Onan diesel genset inscrutable problem

Great suggestions. I did install an electric pump and even with the pump feeding from a jug the problem is there. So, its no a fuel line or primary filter issue. The "error" does not go away. On these generators, when they stop the LED on the switch blinks to indicate the reason for stopping. 3 blinks means fuel problem. It will restart right away. I will check without the remote panel and also check the connectors.
The overheating does not occur with the sound shield off and a cheap box fan blowing on it. Its a $20 solution that I can live with.



Why can't things remain where i carelessly left them?
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Old 03-05-2015, 20:31   #7
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Re: Onan diesel genset inscrutable problem

Does the engine stop with this error when you don't step on that spot in the head?
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Old 03-05-2015, 21:55   #8
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Re: Onan diesel genset inscrutable problem

Quote:
Originally Posted by dohenyboy View Post
I have an Onan genset in my lazarette. Its the MDK 7/9 kW. It runs fine except for an overheating issue (I have heard they all tend to run hot, and solving it with an auxiliary fan)

The genset stops and I get the lack of fuel error message (3 blinks) . It stops, instantly, when I step in a certain spot on the floor in the aft head. This spot is on the other side of a bulkhead about 2 feet away from the generator. There are no wires or anything under the floor that could be moved or squeezed by my stepping on it. The hull is aluminum and plenty big, so its not a question of the boat tilting to one side or the other. I first thought somehow the fuel line which runs three feet away was being squeezed somehow. I replaced the entire fuel line. No help. I tried running the genset from a jerry can with the same results.

I have only 140 hours on the genset over the past couple of years for this very reason.
Any ideas other than consulting a shaman?
I have sailed many thousands of miles on boats with the 7.5 MDKBJ (working in one of them right now), which I think is very similar. They run at about 72 degrees C unless the impeller breaks, which happens very frequently. If it runs hot there is a problem.

You may have a bit of old impeller blocking passages in one of the ends to the heat exchanger. There is a special cover that lets you access the place where the end of the heat exchanger that matters. The most reliable setup I have seen has an added 120V raw water pump powered by the genset itself, which will push raw water even if the impeller is gone.

Regarding the fuel problem, do you have an external (added) fuel pump or are you making the built-in pump suck fuel from the tank directly? Wat filters are there in between tank and genset?

Get the installation manual and read it, IME all problems with these babies are due to not following the instructions.

Cheers

C
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Old 03-05-2015, 22:07   #9
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Re: Onan diesel genset inscrutable problem

Seems to me if your stepping in the head, you might also be using the loo. Any chance the water intake is from the same seacock? Or an electrical issue if it's an electric dunny. Or the discharge is close to the intake, etc etc.
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Old 04-05-2015, 17:08   #10
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Re: Onan diesel genset inscrutable problem

dohenyboy

Did you fix your 3 beeps?

Air in the fuel line will give the same problem. But you tried with electric fuel pump already. maybe not.

Check again the fuel filters, in-line cartridge filter, hose for hair line cracks or leak.

Try putting a clear tube just before the mechanical fuel pump to see if any air bubbles enter the fuel pump.
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Old 04-05-2015, 21:18   #11
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Re: Onan diesel genset inscrutable problem

A major clue tonight. I was in the lazarette emptying the holding tank. After completing that task, I stood up in the hatchway about 2 feet to the stern of the generator. I have some plywood laying on the stringers to make it more comfortable. As I stood up, the generator started to crank over for a couple of seconds.
Definitely there is some kind of loose or chafed wire...... or a problem on the control board....To be investigated at morning light.
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