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Old 12-11-2019, 03:40 PM   #1
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Shocking Onan

Hi All I have a 1977 Onan MDJA 7.5 that has not been running in a while. I go to start it and it fires up right away but dies as soon as I release the start switch. At this point I went down to the engine room to investigate and tried holding the start/stop solenoid in the run position and hit the starter on the unit. It started right away but gave me one hell of a shock from both the switch and the solenoid(anything metal). Where should I be looking for the problem?
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Old 12-11-2019, 03:48 PM   #2
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Sorry its an Onan MDJE not a MDJA
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Old 12-11-2019, 10:12 PM   #3
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When the start switch is pressed, the shut down safeties (oil pressure, water temp and maybe has exhaust temp) are bypassed. Problem could be the senders, the wiring, or a relay. Shock is a bad ground at least. Could be you have corrosion where the ground attaches and could be the cause of not running.
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Old 12-12-2019, 06:39 AM   #4
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You have a bad ground and possibly a mis-wired gen output circuit. And possibly a winding fault in the generator end. If not familiar with electricity and generators, get a pro to check it out. A strong shock means it is not a 12vdc fault, but a fault on the 120/240vac side. Be safe, this could leave you dead in the engine room.
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Old 12-12-2019, 10:39 AM   #5
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My 1978 MDJE-3CR (7.5Kw) did the same thing. I believe I had to mess with the rotary switch. (It was about 4 years ago. Sorry my memory is so vague.) If you don’t have one already, download the technicians repair manual. The manual is designed so that any idiot can trouble shoot using flow charts. The manual covers about a dozen or so Onan models so don’t use 7.5 or MDJE in the google search.

You would be better off going to the Onan forum at smokstak for asking this question and finding the manual to download. You would also find my old forum post I made concerning my problem and fix.
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Old 12-12-2019, 01:15 PM   #6
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Thanks All! Snotter I have now joined smokstak but am waiting approval before I can post or search. Do you have the manual's #? What rotary switch are you referring too? The one at the remote start that changes from shore to genny?
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Old 12-13-2019, 01:24 PM   #7
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You can download the MDJE manual here:

http://www.grandbanksowners.com/memb...%20Catalog.pdf
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Old 12-13-2019, 01:35 PM   #8
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Thanks Gilberto I have this manual I'm looking for the Tech Repair Manual
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Old 12-13-2019, 01:39 PM   #9
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Try these:

http://www.grandbanksowners.com/memb...%20%201of2.pdf

http://www.grandbanksowners.com/memb...%20%202of2.pdf
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Old 12-13-2019, 01:58 PM   #10
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As Snotter had mentioned there is a tech repair manual with a flow chart for idiots. I'm the idiot that needs the flow chart.
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