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Car Forum / Driving, Maintenance, Tuning / RVs / March 2007

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Questions on Onan Generator Microquiet 4000 Carburetor

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Jay Alperson - 10 Mar 2007 23:47 GMT
Would anyone please post or email me pictures of the throttle linkage on an
Onan Microquiet 4000?  I was not getting any gas; I took it off and I am not
sure whether I have the linkage set correctly.  Also, it now floods badly; I
thought the float was messed up, but I think it is ok.  Whenever I try to
start it, I get lots of white smoke...  The spark is fine.

Also, what is the brass fitting at the bottom of the float chamber and that
attaches the housing of the chamber to the carburetor?  It has 2 wires, one
to ground and a red wire to somewhere else...

Thanks for any info...
Alan Robinson - 11 Mar 2007 05:36 GMT
> Would anyone please post or email me pictures of the throttle linkage on
> an Onan Microquiet 4000?  I was not getting any gas; I took it off and I
[quoted text clipped - 7 lines]
>
> Thanks for any info...

Sorry I don't have a picture to send you - maybe a verbal description will
help.

The throttle link is the rod with the spring around it - it runs from the
governor arm to the right-hand (closest to the engine) bellcrank on the
carburetor. The governor spring should hold the throttle wide open when the
genset is not running (the tab on the bellcrank will be as far away from the
idle stop screw as it can get). You should be able to move the governor arm
against spring tension to close the throttle (the tab on the bellcrank
touching the tip of the idle stop screw).
The choke link is the rod without the spring around it - it runs from the
choke spring (in the housing on the exhaust pipe) to the left-hand (closest
to the air cleaner) bellcrank on the carburetor, and when cold, should hold
the choke plate almost closed. Note that this bellcrank has two parts - the
tab the link attaches to, and a second piece that is actually connected to
the choke shaft, and has a tab that the throttle bellcrank hits when it
moves to the closed throttle position, with a spring between the two parts.
The effect of this is that the choke can only be fully closed when the
throttle is wide open - when the genset starts to run and comes up to speed,
the governor will close the throttle which will force the choke to open
partway - even though the tab connected to the choke spring may still be
calling for full choke. As the engine warms up, the choke spring will uncoil
and move its end of the link so that it calls for less and less choke.
The brass fitting on the bottom of the float chamber is an electrical fuel
shutoff valve - it prevents fuel going from the float chamber to the main
and idle jets unless it is energized (and it is only energized when the
genset is supposed to be running). This is done to prevent the genset from
'dieseling - running on - pick your term' when shut down.
From your description 'lots of white smoke', it certainly appears to be
flooding - either you have the choke linkage messed up so it can't open the
choke as it starts to fire, or you have a float/needle/seat problem in the
carburetor.

Alan
Jay Alperson - 13 Mar 2007 00:14 GMT
Thanks for the info!  I didn't know the technical names for the parts of the
carb.  I'm betting on a float/needle/seat problem.  I think I will pull the
carb again and try to assemble the needle differently in the float.  I put
it inside a tab; next time I'll try putting it above the tab.  A diagram
would sure help! I tried testing it before by insuring that it would close
when I manually moved the float upwards; when I blew in the gas inlet, it
stopped letting air in...

I still am getting the white smoke, unfortunately.  The float assembly has a
needle

>> Would anyone please post or email me pictures of the throttle linkage on
>> an Onan Microquiet 4000?  I was not getting any gas; I took it off and I
[quoted text clipped - 44 lines]
>
> Alan
 
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