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Onan Generators

No Start When Cold


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  #1  
Old 04-10-2018, 01:12:07 PM
Gatorgetter Gatorgetter is offline
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Default No startwhen cold...

can anyone tell me what the red button in in the picture. when cold the gen will not start, but if you hold the red button out it starts right up.
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Old 04-10-2018, 01:23:41 PM
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Billy J Shafer Billy J Shafer is offline
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Default Re: no start when cold

Looks like a primer button.
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Old 04-10-2018, 01:26:39 PM
len k len k is offline
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Default Re: no start when cold

After engine sits for some time (maybe a day ??) air can diffuse in and replace propane in hose to carb. Pressing it for 1-2 seconds before starting flows propane thru hose to purge any air in hose.

Keep watch of your oil level. It's only got ONE quart!!
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Old 04-10-2018, 02:50:34 PM
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Default Re: no start when cold

If the primer solenoid STAYS Open while cranking, it could be "flooding" the engine with too much propane. You say it will start if you hold the button OUT and doing that, you are not letting the primer enrichen the mixture. The red button is adjustable with a rod at the regulator side of the button. Mark where the red button is currently set at. I believe turning the red button/knob COUNTER-CLOCKWISE will bring the knob out further and thus not push the regulator diaphragm as far and not flow as much propane when activated.
I have that same regulator on my dry fuel 7.5JB. I have a separate momentary switch to activate the solenoid. I hold mine no more than two seconds and that purges the line to the engine.
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Old 04-10-2018, 03:08:56 PM
Gatorgetter Gatorgetter is offline
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Default Re: no start when cold

Thanks for the input. The unit pulls the red button in when I try to start it and then will not start. But if I hold out on the button and prevent it from going in the gen starts right up. The problem seem to be the button engaging when it shouldn't. should it be screwed in or out for this adjustment. yes i have been keeping a careful eye on the oil ...thanks. the gen only has 150 hours and runs great when I get it cranked , it just a little cold when I have to get out of the camper and hold the red button to start it LOL
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Old 04-10-2018, 03:11:29 PM
Zeromedic Zeromedic is offline
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Default Re: no start when cold

Quote:
Originally Posted by Gatorgetter View Post
can anyone tell me what the red button in in the picture. when cold the gen will not start, but if you hold the red button out it starts right up
Hi Gatorgetter,

As Billy says, that is a solenoid primer on the demand regulator.

If you are holding it -out- as you state, you are disabling its function. You
might just want to disconnect one of the leads to it and see how things work out.
(the primer was discontinued on later models)

If you want to try and keep it original, try adjusting it. To do so, hold the metal
disc and turn the red knob out a quarter turn at a time for less prime or a quarter
turn in for more.

The initial setting is all the way in (gently), then 1 1/2 turns out.

Steve

hehe, looks like Motorhead and I were both typing the same things at the same time.
I think that's the first time that has ever happened here. not.

Also, 981-0518 in the repositories is your service manual.
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Old 04-10-2018, 03:18:40 PM
Andrew Mackey Andrew Mackey is offline
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Default Re: no start when cold

Not sure, but Billy could probably confirm or deny - the unit may have a sensor that tells it it needs to be primed (cold temp). Usually a prime is not necessary unless it gets below 35 degrees F or less. You may have a bad thermostatic sensor, if your unit has one. Otherwise, perhaps a manual momentary switch needs to be put in line, so that you can prime if necessary (Normally open switch). You push the switch if you need to prime (close the circuit, activating the solenoid).
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Old 04-10-2018, 03:20:57 PM
Gatorgetter Gatorgetter is offline
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Default Re: no start when cold

Thanks guys I'll give it a try
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Old 04-11-2018, 10:36:07 PM
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Default Re: No Start When Cold

OK random thoughts and questions. ...... if this is a cold start solenoid it should not engage when the temperature is below say 35° . So when it's cold and I hold out on the solenoid am I giving it more or less fuel. At 77° today the gen fired right up . It may be a bad thermostatic switch. If I put a momentary normally open switch in line with the green wire it should give me the ability to leave the solenoid disengaged for a cold start. Thought , comment's ,
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Old 04-11-2018, 10:56:47 PM
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Default Re: No Start When Cold

I am not sure about the systems on that model. But I would guess it would be like a preheat for a diesel. If it has such a system.
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