Why Do Onan Generator Not Like The Cold Weather???

[cimplexsound]

As many of you may know my Ford Fleetwood Flair Class A 30 foot has an an electric start Onan Emerald Genset 1. Mine along with so many other Onan generators seem to intensely dislike running in cold weather until it's warmed up. This morning I went to hit the start button and it acted like a dead or low battery. I checked my house battery which was at almost 14 volts and charging. I hit the start button a second time and the motor did turned over. This is obviously a cold weather issue. It's about 41 Degrees outside in Southern Nevada this morning. I've owned all kinds of carbureted gas motors that never had an issue with cold weather. They were also stored outside. My genset also hunts when it's cold so I keep my hand on the governor's sweet spot to help it along, it then runs fine once the motor is warmed up. So my question is. Why do Onan Generators have such a hard time in cold weather???? I'm counting on you to help me solve this mystery that is so notorious to Cummins Onan generator. So your feedback is much appreciated.

[FIRE UP]

Originally Posted by cimplexsound

Attachment 187627
As many of you may know my Ford Fleetwood Flair Class A 30 foot has an an electric start Onan Emerald Genset 1. Mine along with so many other Onan generators seem to intensely dislike running in cold weather until it's warmed up. This morning I went to hit the start button and it acted like a dead or low battery. I checked my house battery which was at almost 14 volts and charging. I hit the start button a second time and the motor did turned over. This is obviously a cold weather issue. It's about 41 Degrees outside in Southern Nevada this morning. I've owned all kinds of carbureted gas motors that never had an issue with cold weather. They were also stored outside. My genset also hunts when it's cold so I keep my hand on the governor's sweet spot to help it along, it then runs fine once the motor is warmed up. So my question is. Why do Onan Generators have such a hard time in cold weather???? I'm counting on you to help me solve this mystery that is so notorious to Cummins Onan generator. So your feedback is much appreciated.

Well Sir,
First off, a couple of things here. 1st, how well have you kept up on the maintenance? That is, you say your battery is at or close to 14V which is good but, do you have a good, tight and clean connection to the generator itself from the battery positive and, are the starter connections clean and tight? 2nd, If I recall, (used to have an Onan that looked identical to yours) there's a couple of adjustments on them. One is for colder weather application and warmer application. And is there a "Altitude" lever or not? Can't remember.

Cranking, or lack of it, is normally a cable connection or condition problem or a battery status problem. You say yours is at 14V but, again, is it at 14V at the connection point on the gen set? How many hours on the gen?

Now, running or, problematic running (at least in gas gens) is normally a carb or choke issue and or, maybe as stated, the lever for "colder" or "warmer" operation may not be in the correct position, just guessing here. If the engine cranks good, at first push of the start button, but does not start, there could be a fuel problem too, or lack of it. There's a few things to check out here. Hope some of this helped. Keep us informed if you find the cause(s) of your issues so that others may learn.
Scott

[cruzbill]

Hunting can be caused by dirty carb, and the start issue might be resolved by running the choke a little more rich. Jets? What's the elv of Vegas again? New plug(s)? 5-20 oil?

[l1v3fr33ord1]

cimplexsound-

Perhaps your generator could benefit from a priming circuit:

The Lazy Daze Companion: Adding A Primer Circuit To Older Generators

[Forkyfork]

I have an Onan 7000 and it started and ran fine in 28* weather. It is 14 years old but it only has 300 hours on it. Near as I can tell it has been started regularly and maintained.

When was the last time you cranked your generator. Every two weeks is recommended. Run it at least an hour with a load. I run a space heater in the winter in the summer I run the AC.

If you checked your house battery while it was charging and it read 14v you were reading the charger not your battery. To get an accurate battery indication you need to disconnect the charger, let it sit an hour or so and then check it. Also a multimeter or house display is not the same as checking with a tester that uses a load.

Some things to consider. Yours is an emerald and older. Are all Onans having issues or is it actually normal age/maintenance related issues?

My experience with small engines (motorcycles and boat motors) that use carbs is the rubber diaphragms in them deteriorates, the jets need maintenance, the floats deteriorate and don't float properly fuel pumps fail on and on.

I used to take in lawnmowers that people gave up on. Half the time draining the float bowl that had more water than fuel resolved the issue. My OB on my boat is a different story. The carb diaphragm has to be changed every couple years I stock pile them. lol

Keep it simple. Don't bury the thing based on speculation that all Onan emeralds are bad. Could be as simple as air fuel ratios. They are old and will need maintenance repairs at some point.

[alank]

From what you describe, I'd take the carb off and give it a good cleaning. The "searching" after it starts, but isn't warmed up indicates the automatic choke is set too lean. If the components allow for it, loosen the screws on the choke spring housing, start the gen., then when it starts "searching" very slowly tighten the spring to increase the choke to see if there is a point the searching quits.

[YC1]

Nicely said Fireup, as usual just spot on.

Fresh plugs can make a big difference. And be absolutely sure they are the correct ones. I managed to get some plugs the other day for my boat and it ran poorly. I put the old ones back in and it runs fine. Guess I got them crossmatched incorrectly.

Another thing that can help is Sea Foam. I have seen it do amazing things to some rough running engines.

[Soppy]

Typical Onan operation in my opinion. They are set up to run on the lean side for fuel economy . In cold weather , the automatic choke opens too quick and the engine does not get enough fuel to run smoothly. As the parts wear out , it only gets worse. On a generator , the tight tolerances on the governor only make the hunting worse.

[electrowood]

Originally Posted by cimplexsound

Attachment 187627
As many of you may know my Ford Fleetwood Flair Class A 30 foot has an an electric start Onan Emerald Genset 1. Mine along with so many other Onan generators seem to intensely dislike running in cold weather until it's warmed up. This morning I went to hit the start button and it acted like a dead or low battery. I checked my house battery which was at almost 14 volts and charging. I hit the start button a second time and the motor did turned over. This is obviously a cold weather issue. It's about 41 Degrees outside in Southern Nevada this morning. I've owned all kinds of carbureted gas motors that never had an issue with cold weather. They were also stored outside. My genset also hunts when it's cold so I keep my hand on the governor's sweet spot to help it along, it then runs fine once the motor is warmed up. So my question is. Why do Onan Generators have such a hard time in cold weather???? I'm counting on you to help me solve this mystery that is so notorious to Cummins Onan generator. So your feedback is much appreciated.

I have the same generator. On the filter there is a summer/winter lever, make sure it is in winter position. This will operate properly if the flexible hose is in position on the back side of filter. The altitude adjustment probably adjust the mixture. Mine runs better set for higher altitude than actual. It seems that when it sets a few weeks gas runs back into tank and I have to crank it a couple of times for the "lift" pump to get fuel to carb. I have changed my "lift" pump a couple of times because I had flow but no pressure (should be 3-5 psi). These pumps have a diaphram type system that get hard and lose there effectiveness. Check fuel filter.

Starting issues, electrical, sould be diagnosed at generator solenoid connections. Could be bad connection, defective solenoid, or defective starter. I changed the local start/stop switch because it was stuck in the "stop" position and would not crank. The engine seals in, or continues to run, when the regulator and oil pump are active. Hope this helps and good luck.
Ken

[cimplexsound]

Originally Posted by FIRE UP

Well Sir,
First off, a couple of things here. 1st, how well have you kept up on the maintenance? That is, you say your battery is at or close to 14V which is good but, do you have a good, tight and clean connection to the generator itself from the battery positive and, are the starter connections clean and tight? 2nd, If I recall, (used to have an Onan that looked identical to yours) there's a couple of adjustments on them. One is for colder weather application and warmer application. And is there a "Altitude" lever or not? Can't remember.

Cranking, or lack of it, is normally a cable connection or condition problem or a battery status problem. You say yours is at 14V but, again, is it at 14V at the connection point on the gen set? How many hours on the gen?

Now, running or, problematic running (at least in gas gens) is normally a carb or choke issue and or, maybe as stated, the lever for "colder" or "warmer" operation may not be in the correct position, just guessing here. If the engine cranks good, at first push of the start button, but does not start, there could be a fuel problem too, or lack of it. There's a few things to check out here. Hope some of this helped. Keep us informed if you find the cause(s) of your issues so that others may learn.
Scott

Lets see. Motor oil changed ever 50 hours of operation, new sparks plugs every 3 to 6 months, the air cleaner checked once every 2 weeks, the electrical connections are checked frequently and the stator is cleaned out once every 3 years along with a good cleaning of the brushes and slip rings to make sure the genset is kept in top condition. It also has a new fuel filter and pump. I also run Sea Foam through this generator on a regular basis. Yes it is very well maintained. I started it in 64 degree weather today and it ran perfect. So it is cold weather. I have a few RV experts including an Onan genset mechanic tell me it's just the way Cummins motors manufactured these things. I do think however the starter motor is going out because of that classic sickly whining sound when a starter goes bad. Or a bad starter relay switch. Otherwise it runs great. Can't get at the starter unless I pull the generator out. So I'll check the relay switch first. Otherwise Note this is a 500 pound genset so that's a project for another day. Starters are pretty cheap for this generator. But it's getting at the starter that's a while lot of work. 😓


1979 Dodge Tioga Class C 24 foot. 1987 Fleetwood Bounder 34 Foot.

[cimplexsound]

Originally Posted by electrowood

I have the same generator. On the filter there is a summer/winter lever, make sure it is in winter position. This will operate properly if the flexible hose is in position on the back side of filter. The altitude adjustment probably adjust the mixture. Mine runs better set for higher altitude than actual. It seems that when it sets a few weeks gas runs back into tank and I have to crank it a couple of times for the "lift" pump to get fuel to carb. I have changed my "lift" pump a couple of times because I had flow but no pressure (should be 3-5 psi). These pumps have a diaphram type system that get hard and lose there effectiveness. Check fuel filter.

Starting issues, electrical, sould be diagnosed at generator solenoid connections. Could be bad connection, defective solenoid, or defective starter. I changed the local start/stop switch because it was stuck in the "stop" position and would not crank. The engine seals in, or continues to run, when the regulator and oil pump are active. Hope this helps and good luck.
Ken

It's complete no hoses missing. I do run it in winter position for temps under 54 degrees. Thank you I will check the starter relay. It's located just behind the main circuit board that has the Start/Stop button so this is a piece cake to check. It has a new fuel filter and I also put a new fuel pump in so this genset has been checked over in every aspect of the word. Thanks again.


1990 Ford Fleetwood Flair 30 Foot
1987 Fleetwood Bounder 34 Foot.

[cimplexsound]

Just to make it clear to everyone Onan gensets do not have a starter solenoid. They have a relay switch usually in the control box behind the main circuit board (that has the start/stop switch at the generator) usually hold in place by four torque screws.


1979 Dodge Tioga Class C 24 foot. 1987 Fleetwood Bounder 34 Foot.

[Dutch Star Don]

I've had two gas and two diesel Onans and have never had an issue. On my 4K gas unit, it had the altitude lever and cold weather lever. We live in California, but do Yosemite once a year at Thanksgiving. Before starting at Yosemite, I would adjust the altitude lever and switch to cold air. Never a problem.

[cimplexsound]

The battery is now replaced. New house battery in. I'm glad it was under warranty because the original was $150 bucks. I think it is a bad starter motor or relay switch. Again there is no starter solenoid in an Onan Emerald series generator. So I'm checking the relay first. with the genset weighing almost 500 pounds. If its the starter I'm taking my slow sweet time to get this fixed. I'll have a couple of my mechanic friends help me pull the genset out. Other than the starting issues, after a little tweaking this generator is running good, really good now. So thank you. It does seem to prefer warmer weather however. Will keep you updated.


1979 Dodge Tioga Class C 24 foot. 1987 Fleetwood Bounder 34 Foot.