Onan generator problems.

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golftrip

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Mar 5, 2006
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15
I have an onan generator on my 1977 Dodge.  The fuel pumps seems to be working however it starts hard.  If I spray some starter fluid in the air filter, it starts right up, no problem, then will continue to run just fine.  If I shut it off, wait a few minutes, even a few hours, then it will start right up again, but if I wait overnight, she won't start up again, till I get out the starter fluid spray.  I put in brand new plugs, but no difference.  Any help is greatly appreciated, thank you!
 

Gary RV_Wizard

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It sounds as though your carburetor is not vaporizing fuel as well as it should on a cold start.  I would guess it's time for a carburetor rebuild. The tiny passages clog up, o-rings dry out, etc. , especially if not used regularly. This is a fairly common problem on RV generators.

IS there a "cold start" position or a choke? Most older gensets have one somewhere, though it is often not obvious. If you can find it, see if it heps any (even if it is not all that cold outside).
 

Karl

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Mar 3, 2005
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Elkhart Lake, WI for the summer. Work at Road Amer
Gary,

I think you may have hit on it. My Onan has cold starting trouble too. Below about 30F, if I hold the start button, it won't start. If I press it for about 2 seconds, then repeat once or maybe twice, it will. I think the fuel may be draining from the float chamber and the fuel pump shuts off after a short time if the engine doesn't start. That may be why it takes a couple of short start tries to get it going. Looks like I've got a carb. rebuild on my to-do list too! Tnx :) 
 

John From Detroit

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Apr 12, 2005
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Davison Michigan
I find that on My Onan if I hold the start button,, It may start, Eventually (Usually starts, not always)

However if I tap the button, just tap it is all, (turns it on) and then in about 30 seconds press it, it fires right up

My rig is a gas buggy (not desiel) so the generator runs on volital gas, as opposed to Disel

My theory is evaporation, that fuel in the carb bowl simply evaporates between uses.

NOTE: I used to have a car with an electric fuel pump... (in fact my current car has one) and it works much the same way... If I turn the key to ON, wait a few seconds and then crank, much easier to start in the morning (or anytime it's sat for a long time)  Same theory
 

golftrip

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Joined
Mar 5, 2006
Posts
15
I am planning on taking the carb off and rebuilding it, if I can find a kit.  I will try the method descirbed above, push start, hold for a few secs, then wait, then try it again..Thanks for the help all.
 

John From Detroit

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Apr 12, 2005
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Davison Michigan
Try "Tap Start" (momentary push) instead of "Push and hold"  Then wait for a few seconds (like 30 seconds) and push to start... This appears to be normal operation by the way
 

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