MDKD onan Problem

[Bill Allen]

Robin thought I should post this, i've been having a shut down problem with my genset. It would run for twenty minutes (about) then shut down. Restart it and run for maybe five minutes. Checked all the shutdowns, changed filters, trouble shut everything we could. Never had to reset the shut down button. Talked to my generator guy since I didn't have to reset he sugested it was either the shut down reset or the fuel shut off solonoid. Replace the reset in the keys thought it was fixxed. Left the keys and it started it's games again. Had the solonoid on hand so changed it, no diference. Called my generator guy once again he was stumped but said he would call another buddy of his in the business and pick his brain. He called back said his buddy had a situation where the 30 amp fuse holder between the starter and control circut had gotten hot and took the spring tension out of the fuse holder and although it wasn't doing quite the same thing as mine he sugested changing it out. My first thought was bullshit, but nothing else seemed to be wrong with the unit so I changed it out, really didn't look bad to me. Started the geset up and that was it, i'm still amazed, but it is an Onan. Ever get up in North Jersey and need a very good generator guy Call Heman and his sons at Ocean Power. Bill

 

[REBrueckner]

This is a 1974, 7.5KW ONAN. I'm guessing this fuse is between the +12v dc at the starter and supplies the entire genny controls with 12 volt. Bill, is this an inline fuse???

Yea, I thought this was interesting and worth a post as I did not know there was such a fuse on this model genny....There is no such fuse I am aware of on my prior 12KW 1972 ONAN so I never thought to ask Bill about any fuses while troubleshooting this situation....

We did not have a schematic along while Bill and I traveled aboard his boat from Brielle NJ to Marathon Fla last November. Bill or I disabled and invididually checked each of the control circuit shutdown sensors....and the symptoms did not change.

As I recall, the genny ran for a longer period when starting from a cold condition...maybe the 15 or 20 minutes Bill mentioned. We could restart it and it ran strong without missing but when hot would only run for maybe five minutes before shutting down. So we suspected something associated with a heat sensor.....but it wasn't.

As I recall, one of us put 12 volts directly on the fuel shutdown solenoid and that kept the genny running normally. I don't remember the source we used but I guess it bypassed the fuse which was the source of trouble. We were reluctant to run the genny that way fearing there was something legitimate causing the shutdown that we did not recognize.

That an expert knew of this problem suggests we are not the only ones to fall victim to this problem. So if your genny of any model has such a fuse on the genny it would be a good idea to pull the fuse holder apart and manually stretch (extend) the spring...seems like they may get weak with age....

 

[Bill Allen]

Everything Robin said is correct except the vintage it's newer then that. The fuse is an inline about a 12 gauge wire (30amp fuse) that runs beside the ground and neutral wires that feed the starter. Also we didn't power the fuel shut down I used a pair of visegrips to keep it open. Bill

 

[Bob Bradley]

I hate to be a "Debbie Downer", but I wound up replacing my MDJE 7.5 two seasons ago because the safety system on it was "so good" that it never let it run for more than a couple hours before shutting it off. It didn't overheat, had plenty of oil/pressure, fuel, etc, but the best I ever managed was about 12 hours of running before she'd shut down - usually 80 miles out while fishing the canyons.

I bit the bullet and put in a 9kW Norpro and never looked back. It's operated flawlessly for well over 200 hours since Aug of '09.

 

[nor'easter]

I had a similar problem on my 1995 8kw, although the run time seemed to be a little shorter if I remember correctly. My problem was the fuel solenoid. I replaced that and it ran well for the last year I owned it.

 

[sunset grill]

We had an issue last year on our 1988 8kw. It was a part on the circuit board. The Onan Manual said replace the board, which was $350ish. We replaced the relay for $20ish. It has run well since. Steve