onan emerial gen set 6.5

[4104GA]

Hi all you onan guys.  My generator will run with the start switch held on start but quits when released. Where
do I start with this one? Thanks for any help with this.
4104GA

[TomC]

Most likely the low oil pressure sensor.  Good Luck, TomC

[JohnEd]

Or that switch you have your finger on.   Got schematic?


John

[Barn Owl]

Onan links that I use:

http://asavage.dyndns.org/Onan/display1.php?Path=900-0337&db=Onan&table=900_0337&Page=019

http://users.california.com/~eagle/list.html#GEN

http://www.smokstak.com/forum/archive/index.php?f-1.html

http://www.gmcws.org/Tech/onan_electronic_ignition/onan_electronic_ignition.html

http://www.gmcws.org/Tech/dsimmons/onan/onan.html

http://www.funroads.com/onanstore/osHome.jhtml

http://www.perr.com/onan.html

[WEC4104]

I have personally seen this on my Onan, (although slightly different model).  Several different things can cause this.  Basically, when you hold your finger on the start button, it temporarily overrides some of the circuits that are active in the normal run state.

For example, as TomC indicated, it could be your low oil pressure sensor. While the start button is held, this safety shut down circuit is bypassed.

Also, if the generator in running but it is not producing AC power, my Onan has a circuit that will shut it down. You might try throwing a meter on the AC output side while someone keeps the generator running using the start button.

I have seen an instance where my Onan only provided power to the fuel pump while the start button was held.  It would crank for a while before it would start. Then when I released the start button, it would run for 5-10 then stumble and die. (fuel starvation).  That was traced back to a problem with the main control board.

I also discovered one time that I had a defective rectifier on the main circuit board.  Fortunately the rectifier is low cost and easy to replace.

[4104GA]

Thanks guys.  I found that my gen has no ac output so will check it out.
 Sam

[TomC]

I went through two 6.5 Emeralds on my big rig before shutting down.  The first went through 12,000hrs without ever having the heads off (much to the amazement of Onan).  I am more then familiar with all the problems typical Onans have.  That's why I bought a Powertech 10kw Diesel genset with all mechanical controls. With almost 500 hours on it, zero problems (like 20,000 miles).  My truck conversion is going to use a 13kw Diesel genset from Wrico, since Dick can build the gensets with mechanical controls or electronic controls.  My preference is for mechanical controls-so what if you have to physically hold the pre-heat switch for 10-20 seconds?  Plus it uses Bosch mechanical relays that are easily obtainable at most any auto parts store.  Good Luck, TomC

[Fred Mc]

I have a Maqyuis 7000 Onan Generator that has a problem with the generator part. Engine runs fine. I bought this for a song thinking I could fix it. However, when I got it I discovered that the circuit board was missing. Onan wants a fortune for one and there are aftermarker boards avialable for $100 or so. The problem with an aftermarket is that Onan will not test it with an aftermarket board so they probably won't diagonse it so I know what to change in the generator.

Does anyone know someone who has used parts for these things or how I can go about fixing it.

Thanks

Fred Mc.

[pvcces]

If you decide to take the gamble and replace the board, be sure to check out Dinosaur. They make some good boards for fair money.

Tom Caffrey

[niles500]

Did you FIRST reset the breaker at the Genhead?

[4104GA]

 :'(Yes the breakers were reset with no help. Going to the shop on Friday to get the pros check it out. Thanks
    for all replies.  This unit has not been used in several years but it did start one time and ran for thirty min.
before I shut it down.  No start after that.
   Sam

[Hartley]

Most Onans including the diesels have a "HOLD-RUN" relay inside the control panel.
It is powered by the A.C. Output of the generator section. They are usually 120 v.a.c
relays.

If that relay gets fried due to someone fiddling with the throttle or an engine surge that causes the voltage controller to fail the relay may need to be replaced. But most are soldered onto the engine control board. ( usually means buying a new board $400 or so. ) Then if the Voltage control board got cooked that is as much or more than the engine board. Those relays don't like 185 volt surges at all.....

Never let anyone fiddle with the throttle linkage or governor linkages even if they tell you that "surging the engine will blow the carbon out !! Yikes "...

Some of the diesels also have a fuel pressure switch that shuts down the electric fuel pump if the "RUN" relay is not locked on. Let off the button and it quits...

I have been around this stuff way too long I fear.....