MDJE 7.5 Problem

[RTyler]

Over Memorial Day weekend the genset ran fine, no problems at all. Yesterday I got to the boat and had the following issues:

1. Starboard side batteries were low, but could just start engine without parallel switch.
2. Genset remote hour meter was clicking away.
3. Genset had no response to start switch.
4. Hit reset button, still no start.
5. Turned off main genset switch and noticed that stop solenoid disengaged. Turned it back on and solenoid re-engaged, and DC ameter indicated 5 amp draw.
6. Turned main switch back off and waited about an hour. Returned, turned on main switch and genset started. I shut it down, and it reverted back to no start.

Question, does this sound like a bad solenoid, or bad sensor?


Robert Tyler

 

[REBrueckner]

Bad sensor..or activation device, not the solenoid....

Am not familiar with the SPECIFIC wiring and shutdown sequence for 7.5KW's; I've had a similar problem in the past with my 12KW...the whole thing is posted here at Sams with excellent inputs from others....

Wait til you get inputs from 7.5KW owners before acting, but if you don't, see if you have points which open for stop and close for run...these are likely mounted on the flywheel housing (inside a container "box" and centrifugal switch operated thru a fiber pin, maybe 3/4" long, activates the points....my problem was eventually traced to the fiber pin which opens the points; it was worn short, after 34 years, so the points would not open/close properly... operation was intermittent....same symptoms as yours....intermittent operation was due, I believe, to a wear grove in the end of the pin....It would sometimes "stick"....hence sometimes started, stopped, properly, sometimes did not. You may be wired differently with somewhat different mechanisms...
The fiber pin and related mechanism in the current parts catelogue looks slightly different but the fiber PIN identical to my 1972 pin...For a dollar or so, plus shipping, it was worth the risk..and it's worked fine for several years now...

 

[RTyler]

Thank you for the input. I'm assuming that it is not normal for the solenoid to remain energized after a shutdown from a sensor that is working properly. It seems that once the engine shut down the solenoid would release and not draw current. So I guess it could be a faluty sensor or as you suggest something in the shut down sequence. Hopefully someone with a 7.5 could weigh in if they have had a similar problem.

Thanks again.

Robert Tyler

 

[BUSTER]

I would suspect Rob is right.The control relay for the fuel solenoid is a double electro-mangetic "similar to ignition contact points" switch,unless you have upgraded to the solidstate control system.Perhaps the contact point have welded themselves together?I would take the cover off the control box and ring it out with a volt meter.

 

[REBrueckner]

RT,
The fact that the solednoid is energized and then releases suggests its probably ok..If it hangs up, in the on position again, and you can trace some of the wires, using the owners manual schematic, lift/loosen the one going to the contacts/points and determine if that causes the solenoid to click off...if so the points are closed as Buster says...

Over the years, I have attached dymo labels to many of the control box wires as I have fussed with individual ones...so now if I have to muck around down there, I save having to figure out which wires go where...

 

[RTyler]

I down loaded the Engine Control Trouble Shooting Flow Chart from Onan this morning. Assuimg that my starter connections are good, which I think they are because I went through that drill a couple months back; they are suggesting that I test solenoid K1, relay K12, and the Start/Stop Switch. I had not considered the Start/Stop Switch but it does sound like it could be the culprit with the fuel solenoid staying entergized. I've put a call into their Technical Support, hopefully they will call back.

Robert Tyler