Onan generator won't start

Doug Domm · 06-28-2009, 10:13 PM

I have a 1994 Winnebago with a Onan Emerald Plus 4000 that won't start. At first I thought perhaps because the gas gauge was just above 1/4 tank may have been the reason as the fuel pickup for the genset is around the 1/4 tank level as a safety device so as not to run the coach out of fuel while sitting at one spot. Well $100 dollars worth of fuel later still no go. The oil level is not low either as a matter of fact maybe even just the slightest amount above the full line. Checked for spark and there is none, thought perhaps because of one of the previously mentioned but oil and gas are not in short supply. Ok so now if any of you are familiar with these RV's you already know that if the genset is not on a slider they are a real bear to diagnose further and at this point I am just not motivated to remove the genset to gain access. Is there something I am missing here and if I do have to lower the genset what are some typical problem areas to look at on these. I might add it only has 80 hours on it and has always started and ran perfectly to this point. Thanks in advance. Doug

Rich Biebel · 06-29-2009, 06:00 AM

Has the unit sat around not used for a while? Is there any debris laying around or on the unit? Mice like to nest in those units. They almost always find there way up inside the generator end. If it has solid state ignition ( no points) there is a plastic rotor device attached to the end of the crank. It triggers the spark as it passes a fixed pickup. All this stuff is inside the generator end and it is very common for that plastc rotor to break from hitting a mouse or the nest material. Coils don't go bad often on most Onans. If it has points they are in a little box on the top of the unit but I think from the year you describe it has solid state ignition. There is now way to work on these properly without removing them from the MH. I use a forklift or just floor jacks...........

Mark Yacavone · 06-29-2009, 11:13 AM

Have you checked the "low oil" sender ?

Doug Domm · 06-29-2009, 11:32 AM

No signs of mice but the neighbours cat got REAL friendly with one front tire and does it ever smell rank. This cat lifted it's leg like a dog. Did you read lifted as in past tense? Where is the oil sender? Thanks for the suggestions. I hear of things like bad circuit boards or do they only control AC output? Doug

Rich Biebel · 06-29-2009, 12:09 PM

Oil pressure switch is located behind the front sheet metal just above the oil filter. If you have no spark during cranking it is not likely the OPS. as the control board is responsible for cranking functions but it's easy to test. There is a white wire that comes from that switch and gets connected to the control board. It is usally directly under the front panel and comes up from the left side. Unplugging it and trying to start it is safe. I have never seen one actually lose oil pressure.....the switches occasionally go bad but they usually start and shut right down if the switch is bad.......If you unplug the OPS and there is spark from a plug wire......the switch is not to hard to replace in the MH........

06-28-2009, 10:13 PM	#1
Doug Domm Member Join Date: Apr 2006 Location: canada Posts: 251 Likes: 28 Liked 84 Times in 21 Posts	Onan generator won't start I have a 1994 Winnebago with a Onan Emerald Plus 4000 that won't start. At first I thought perhaps because the gas gauge was just above 1/4 tank may have been the reason as the fuel pickup for the genset is around the 1/4 tank level as a safety device so as not to run the coach out of fuel while sitting at one spot. Well $100 dollars worth of fuel later still no go. The oil level is not low either as a matter of fact maybe even just the slightest amount above the full line. Checked for spark and there is none, thought perhaps because of one of the previously mentioned but oil and gas are not in short supply. Ok so now if any of you are familiar with these RV's you already know that if the genset is not on a slider they are a real bear to diagnose further and at this point I am just not motivated to remove the genset to gain access. Is there something I am missing here and if I do have to lower the genset what are some typical problem areas to look at on these. I might add it only has 80 hours on it and has always started and ran perfectly to this point. Thanks in advance. Doug

06-29-2009, 06:00 AM	#2
Rich Biebel VIP Member Join Date: Jun 2007 Location: Northern New Jersey suburbs Posts: 2,314 Likes: 25 Liked 544 Times in 213 Posts	Re: Onan generator won't start Has the unit sat around not used for a while? Is there any debris laying around or on the unit? Mice like to nest in those units. They almost always find there way up inside the generator end. If it has solid state ignition ( no points) there is a plastic rotor device attached to the end of the crank. It triggers the spark as it passes a fixed pickup. All this stuff is inside the generator end and it is very common for that plastc rotor to break from hitting a mouse or the nest material. Coils don't go bad often on most Onans. If it has points they are in a little box on the top of the unit but I think from the year you describe it has solid state ignition. There is now way to work on these properly without removing them from the MH. I use a forklift or just floor jacks........... __________________ Rich Biebel S/C 1479 Stock 147R Last edited by Rich Biebel; 06-29-2009 at 06:17 AM.

06-29-2009, 11:13 AM	#3
Mark Yacavone Veteran Member Join Date: Mar 2002 Location: Miles From Nowhere Posts: 7,790 Likes: 2,881 Liked 5,077 Times in 1,935 Posts	Re: Onan generator won't start Have you checked the "low oil" sender ? __________________ "We are lucky we don't get as much Government as we pay for." Will Rogers

06-29-2009, 11:32 AM	#4
Doug Domm Member Join Date: Apr 2006 Location: canada Posts: 251 Likes: 28 Liked 84 Times in 21 Posts	Re: Onan generator won't start No signs of mice but the neighbours cat got REAL friendly with one front tire and does it ever smell rank. This cat lifted it's leg like a dog. Did you read lifted as in past tense? Where is the oil sender? Thanks for the suggestions. I hear of things like bad circuit boards or do they only control AC output? Doug

06-29-2009, 12:09 PM	#5
Rich Biebel VIP Member Join Date: Jun 2007 Location: Northern New Jersey suburbs Posts: 2,314 Likes: 25 Liked 544 Times in 213 Posts	Re: Onan generator won't start Oil pressure switch is located behind the front sheet metal just above the oil filter. If you have no spark during cranking it is not likely the OPS. as the control board is responsible for cranking functions but it's easy to test. There is a white wire that comes from that switch and gets connected to the control board. It is usally directly under the front panel and comes up from the left side. Unplugging it and trying to start it is safe. I have never seen one actually lose oil pressure.....the switches occasionally go bad but they usually start and shut right down if the switch is bad.......If you unplug the OPS and there is spark from a plug wire......the switch is not to hard to replace in the MH........ __________________ Rich Biebel S/C 1479 Stock 147R Last edited by Rich Biebel; 06-29-2009 at 12:15 PM.