Onan MAJB Marine 3kw- shut down

[rocked]

I guess it's never ending when you use something!

So the gen was running like a champ, and we were anchored out enjoying the TV on Saturday night, when the power just went off. Then the generator shut down. It will start and run as long as the Start button is depressed.

From searching the forum, it sounds like it isn't producing power, but what I'm wondering is does the symptoms "while there was a medium load on it, it stopped and then shut down" point to anything specific?

I will take a multi-meter up next time I'm there and check for sure. I did pull the 3 fuses on the front panel, all looked good. I also flipped the breaker switch on the side of the panel. Also checked the oil and disconnected the temp sensor.

[Elden DuRand]

You might have lost oil pressure or the oil pressure shutdown switch has died.

Make sure oil pressure builds up right after starting - THEN - remove the wire from the oil pressure switch and see if the genset starts and runs normally.

I've got an auto oil pressure gauge with a piece of small copper line attached with a 1/8"NPT fitting on the end. I just remove the oil pressure switch and screw in the gauge line. Now, with the wire off of the switch, I start the engine and check the pressure.

Run the engine as little as possible until you're -SURE - you have oil pressure.

If the switch is bad, you can get one at an auto parts store.

Take care - Elden

[rocked]

I took a mulitmeter up this weekend and no voltage is being produced
(Plus side is she fired right up after sitting for a week...then just died as soon as I let go of the start switch)

[lciambotti]

I am having the same issue. Same Genset. I tried the the oil switch, checked the oil pressure (over 40 lbs), replaced the exhaust high temp switch. Still won't run when I let the start switch go. This happens whether or not I use the remote start switch or the switch on the genset. Anyone have any ideas?

Thanks
Leon

[rocked]

I ended up replacing the bridge rectifier....I'll look around and see if I have a part number. The BR takes the AC current of the alternator and converts it to DC to create the magnetic field (someone correct me if I'm stating this incorrectly.) To get to it, I removed the cover on the control panel, then the gen end cover. (going from memory here). It's a black square about an inch across with 3 terminals on it. If I remember, you can connect an ohm meter to 2 of the terminals (upper right and lower, then upper left and lower) to get a reading. If either of these don't have a 'path', the BR is bad.

[Gunny]

How about posting the whole model/spec/serial number so we see what you see.

[lciambotti]

Thanks. I'll look for the BR. Problem is, where the gen. is located its pretty tight. Not sure if I can get to the end cover. I'll report back!!

[rocked]

For generators in boats, it helps to be a contortionist. Mine was not easy to get to either. Likewise, the timing mark is on the underside of the flywheel necesitating me hanging upside down in the compartment to set the timing.

A little more on the BR. When your start button is depressed, DC voltage is applied from the battery to energize the generator field. Once the generator is producing electricity (AC) and the start button is released, AC is passed through the BR (2 inputs) to the dc output to maintain the gerator field. Think of the BR as a 1 way Y valve. The AC from the 2 poles of the generator are passed to each of the inputs (alternating from one to the other) and out the output as 1 steady stream (DC). The BR Y valve is also only 1 way...so that voltage from the opposite AC path cannot backflow into the other.

[rocked]

Any updates?

[lciambotti]

I replaced the BR yesterday but it didn't help. Actually now it won't even start while holding the start button. I am very frustrated!!!! I've checked and rechecked all my wires, and I just can't find anything.