Re: Onan

seafeverofcuan <seafeverofcuan@...>

Dear Gary,
Thank you so much for such an informed response. A copy of that has already been saved to the ship's computer, it's a pity Onan couldn't explain there own product range in such a straight forward and succinct manner.
The generator burnt out the stator and had to be rebuilt in August last year, since then the Kubota engine never ran smoothly and often shut down indicating an over heating problem. Our laser thermometer always proved it wrong and we simply restarted it and it would run for between twenty minutes and four hours the shut itself down as overheating
and I couldn't source the problem, it was never overheated.
This time the engine stopped dead during normal running while using the washing machine.
Strangely there was no code light, so I was stuck to diagnose the problem, therefore I started from scratch.
First up only 10.65 volts at the starter which proved to be the earth strap from the starter relay to the tray, it looked fine yet when I tugged it, it parted in my hand.
New strap and 12.3 volts up the line from the battery to the starter, yet still no warning code and the engine would not crank .
I employed the local highly recommended service company who are not Onan agents they sent two technicians neither of whom could get it to crank and walked away.
So I went right back to basics again, air, fuel, power, during these checks I pushed the start switch really quickly three times in frustration, and up popped four flashes for over charging.
So even further confused, I followed to the letter, the instructions and got half a crank which made me think there might be an airlock.
So I opened the bleed nut, put a diaper over it cranked some more but still no go. then I switched around the two
K3 AND K4 relays, no difference.
For no good reason I removed the K3 relay which powers the glow plugs, it cranked and started.
I let it run a while shut it down and restarted. Tried it the next morning and it wouldn't crank or start, repeated the process without bleeding and it started although it would not start from the galley switch.
When I left the boat in Mexico it was starting from both switches and running fine and I think that I probably have a problem with either a short in the glow plugs or the starter switch on the generator either or both occasionally drawing voltage away from the starter, certainly Bill's posting re. battery and cables would indicate that as a possibility.
The help line at Onan was worse that useless, never taking time to read my emails and suggesting all sorts of really stupid solutions.
I am now back in Ireland and still waiting for them to tell me who their marine agent is in Mexico.
When I return I intend to be well armed with replacement parts.
Hopefully there is some learning in here somewhere for the group and thank you very much for your help.
Kind regards,


Sea Fever of Cuan

--- In, "Judy and Bill aboard SV BeBe" <yahoogroups@...> wrote:

I found the minimum CCA Cold Cranking Amps required by the Onan MDKAV. It is 360 amps at 12.0 volts.

Now I need to compute the loss of amperage based on the approximately 5 meter run of wire from the battery. If anyone can help with this it will be appreciated. I am not on the boat until next week and I am not sure of the wire size.

BeBe, SM2k, #387
On the hard in Gocek, Turkey with Emek Marine

--- In, "Judy and Bill aboard SV BeBe" <yahoogroups@> wrote:

Gary & all,

Does anyone know how many amps are pulled in the starting cycle?
Starter = ?amps
Glow Plugs = ?amps
Computer, etc = ?amps

I think that in some cases hard starting may be the result of low amperage delivered to the genset. As you know the wire run from the starting battery to the genset is something like 5-6 meters. I have suspected that a higher cranking amp starter battery and/or larger gauge wire, or both is in order. I have found that cleaning positive and negative wire termination points improve Onan starting. This leads me to believe that amps delivered to the starter motor is critical.

I am aware that some owners have increased the positive and negative wire size, some have located a battery closer and some have increased the size of the starting battery. What I would like to know is the amps required vs the amps delivered.

Hope this helps or adds to the discussion.

BeBe, SM2k, #387
On the hard in Gocek, Turkey with Emek Marine

--- In, amelliahona <no_reply@> wrote:

Hi Trevor:

Perhaps you have already solved your problem but let me seek some clarification on your problem. Do you have the shop manual for your genet?

1. I am confused from your post whether this is a problem with the engine cranking or whether this is a problem with the engine running.

a) If the engine suddenly stops, in my experience, this is usually due to one the several sensors on the engine (sea water temp over heat, low oil pressure, etc) telling the engine to shut down. You need to methodically work through each sensor (I don't have my shop manual here but I think there are at least 6 different sensors). They may actually be sensing a fault condition or there may be a faulty sensor, you will have to determine what is the case and repair accordingly. The sensors are mostly either normally open or normally closed switches and can be tested using a multi-meter.

b) If the engine won't crank (turn over as in trying to start it) then you have one of four problems;NOTE: THESE ENGINES HAVE TWO STARTER MOTOR SOLENOIDS (aka CONTACTORS). There is one on the + side and one on the - or ground side. Both solenoids have to work for the starter motor to work crank the engine.

1- a faulty positive side (12 VDC) contactor, check to see if you have 12 volts on the supply side of this contractor, then see if you have 12 volts on the output side of the contractor while someone tries to crank the motor with the start switch, if you have 12 volts in and 12 volts out when activated then this contactor is ok next ,
2- a faulty negative or earth side contractor (starter to ground on the tray). This contactor is mounted below the starter motor and is somewhat out of sight unless you bend way over. If you bypass this contactor you will NOT harm your engine. If bypassing this contactor allows the engine to crank when the start switch is activated then you either have a bad ground or a faulty ground side contactor.
3- a faulty starter motor, If you can measure 12 volts on the supply to the starter motor with your multimeter when the start switch is activated and you have a known good ground side contactor and known good positive side contactor, yet the motor won't crank, then your starter motor is faulty. Just to verify this you can remove the starter motor and take it to a shop to have it tested and/or repaired.
4- a faulty starter switch. If you don't see 12 volts on the control line to the contractors (both + and - side contractors) when the start switch is activated, then you probably have a faulty starter switch.

Once again, cranking (the engine being turned over by the starter motor) is a whole different problem from running. If you have already solved this, please let us know what you found. If not, give us some more details and perhaps we can add some more suggestions.

Best of luck,

Gary Silver
s/v Liahona
Amel SM2000 Hull #335
on the hard at Jolly Harbor, Antigua

--- In, "seafeverofcuan" <seafeverofcuan@> wrote:

Dear All,
my generator stopped dead while running a few days ago. No flashing lights. It cranked a couple of times then silence
I have checked the raw water, fresh water,systems, changed the fuel pump, a suspect earth strap from the solenoid to the tray . I have 12.7 volts at the solenoid if I short the terminals the engine will crank, but I don't want to let in run incase of further damage.
I have swopped over the relays for the starter under the white casing lid, but nothing all I get is the flashing green light at the start switch for a few seconds, I can feel the new fuel pimp working but no engine cranking.
The genset had a new rotor,stator and control panel last October at 1000 hours after burning out.
If anyone can shed some light I would be most grateful. I am in Mazatlan Mexico where the local service companies are willing but have no knowledge or access to Onan.
Many thanks.

Seafever of Cuan
No 425

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