run problem with Onan Marquis 5000 BGM

[MrWizard]

fuel pump approx 6months old - tested pumping good
fuel filter NOT clogged - it is passing fuel, yes enough fuel
yes it has enough oil

it will start , run a few seconds quit

im thinking stuck/bad oil switch
or control board problem

i want to disconnect the oil switch, for testing purposes
but don't know which wire and where

that way i can see if it will run and also Ohm out the switch


thanks
web links and Ideas appreciated

[MrWizard]

thanks for the info
another thing to check

i have purchased a used champion 2000i generator
and using that to power the RVs on board 75amp powermax converter, MW etc..
it won't the A/C compressor, but it will run the blowers and move air around

the compressor surge is just too much for it, with these old A/C units

[bounder39zman]

The early BGM's without electronic governor used a N.O. OP switch.
Later versions used a N.C. OP switch.
On later models, when you energize starter and oil pressure builds up, the governor controller will move throttle rod at carb. to full fuel.
then will stabilize at 1800 rpm when engine starts.
Make sure throttle rod has not become disengaged from actuator (other end of rod from carb).
The "thunk" sound could be many things, It is common for carbon build-up on top of piston and in cyl heads to cause a knocking noise as engine turns over. only fix is to remove heads and clean carbon from heads and pistons. This is actually an ONAN recommended maintenance procedure.

[MrWizard]

Was not just a single thunk
It. Was the same sound every time it turned over, every rotation
I'll charge the batteries and try again

[chuckbear]

I had the exact same problem and fixed it with a new carburetor. But with the Onan, it can be a number of things. They are famous for the oil and overheat sensors going bad. The thunk sound when trying to start might be a low battery. Chuck

[MrWizard]

thanks for the drawing
i would rather Like get to the other end of the wiring at the control board
draining the oil out of the NON-working generator
so i can take the face panel apart to get at the switch wiring
seems to me as the difficult way to do this
like the putting the cart in front of the donkey

update:
tried again to run the genny
after several trys at starting it using the switch on the Onan, it ran for about 20 seconds, then quit.
now when i push the switch, there is 'thunk' sound as it turns over

this does NOT bode well

[RLS7201]

I believe you oil pressure switch is next to the oil filter. Remove the filter and have a look.
I think the switch is normally open.


[img] Click For Full-Size Image. height=400 width=600[/img]
Richard

[Chris_Bryant]

Try looking around at http://m.flightsystems.com/, particularly the Onan troubleshooting guide, which has an oil pressure switch location section.

[MrWizard]

Bump
What no wiring diagrams, no pictures, no Sunday afternoon techs
this is desperate
Need battery charging and the A/C