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Carburetors, Mixers, Fuel Pumps and fuel delivery Discussion about misc. carbs, mixers, fuel pumps, injectors.

Carburetors, Mixers, Fuel Pumps and fuel delivery

Onan 2.5 kv spec. D wont start when hot


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  #1  
Old 11-17-2018, 05:36:43 PM
Yzracer63 Yzracer63 is offline
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Default Onan 2.5 kv spec. D wont start when hot

Onan 2.5 kv spec. D Starts right up and runs great but wont start back up after running at full load for about 10 minutes. I have rebuild the garretson SD demand regulator, replaced fuel lines and clamps, and checked for leaks. It wants to start but just sputters and dies out. also i am testing this with a full tank of propane, new regulator at tank, new control board and voltage regulator from flight systems. recently cleaned the slip rings as well. I can not determine if it wont start while hot due to a fuel delivery problem or something else... any ideas or advice would be much appreciated. thanks
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Old 11-17-2018, 06:33:07 PM
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Default Re: Onan 2.5 kv spec. D wont start when hot

Hello and welcome to the 'Stak.
While cranking engine, give it a short shot of spray carb cleaner and see if it fires. If so, then you have a fuel problem. If not, look at ignition.
Many issues could be part of the problem. Methodical elimination should find what is wrong. Is fuel shut-off solenoid working? Is demand regulator set properly? Is the ignition getting voltage? Is there a high temperature shut-off switch? Does it work reliably? Low oil pressure switch?

Provide the full Model and Serial numbers for the unit and the resident experts here will probably be able to guide you in the right direction.
This post may get moved to the Onan Generator forum by the moderators.
Good luck!
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Old 11-17-2018, 11:43:04 PM
Yzracer63 Yzracer63 is offline
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Default Re: Onan 2.5 kv spec. D wont start when hot

well i was out working on it tonight for a couple hours with no progress at all, and towards the end I was kind of pissed off and just unplugged the main fuel line at the outlet side of the regulator and filled the line with seafoam. it instantly fired off and smoked like a banshee for 10 minuites or so, shut it off and let it sit for a couple minutes. started right back up when i hit the switch, so i did another seafoam treatment. so after doing that twice now it seems to work better than it ever has before.... only thing i can think of is that it had a good amount of carbon build up internally in the motor maybe a hung up valve and it cleaned everything out. i dont know...any thoughts? well see, i will go back out in the morning and do a cold start on it and if it fires right off i guess its fixed!
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Old 11-18-2018, 06:30:33 PM
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Default Re: Onan 2.5 kv spec. D wont start when hot

I got everything back hooked up in the camper, generator runs like a top and starts every time hot or cold. NOW i noticed that when the generator is running with no load and i turn either the propane stove on or try and start the heater, The generator starts reving up like it is starting to run lean or something? And as soon as i turn stove off it revs back down to normal... any ideas or help would be great. thank you!
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Old 11-19-2018, 01:09:50 AM
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Default Re: Onan 2.5 kv spec. D wont start when hot

I know you said in your first post that you replaced the regulator at the tank, but if turning on an appliance changes how the genset is running, then you have a problem with the propane pressure in the system. You really need to get some fittings and clear vinyl tubing, make up a u-tube manometer, and see what the system pressure does with different things running. It SOUNDS like you either have a bad regulator, or a restriction in the line from the regulator to the camper plumbing.

Alan
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Old 11-19-2018, 02:04:01 AM
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Default Re: Onan 2.5 kv spec. D wont start when hot

Correct me if i'm wrong, but shouldn't the generator and all gas appliances be able to run at the same time? As it sits, I can have the generator running along with the fridge, and all 3 burners on stove at the same time, but no heater. as soon as i shut the generator off the heater will fire up first try.
Yes the regulator I put on up at the tanks was one of those mr. heater automatic change regulators for dual tanks. I unscrewed the big plastic plug below the switching lever on the front and noticed there is a screw to adjust spring pressure inside but haven't touched it yet. would anyone happen to know if these regulators are adjustable? maybe it is set too low to run the generator and the heater at the same time?
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Old 11-19-2018, 02:18:02 PM
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Default Re: Onan 2.5 kv spec. D wont start when hot

Wouldn't one want the generator on its own regulator - Separate from any other variables?
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Old 11-19-2018, 07:07:58 PM
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Default Re: Onan 2.5 kv spec. D wont start when hot

Ya That’s what I am wondering to. So the latest is that I can start and run heater and when it’s going I can start generator and they will both sit there and run. When the heater shuts off and goes to start on the next cycle it will not fire up. So it seems like it’s starving for fuel if it’s trying to start when generator is on. And again, as soon as I shut the onan off the heater works like clockwork
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Old 11-19-2018, 11:03:09 PM
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Default Re: Onan 2.5 kv spec. D wont start when hot

Quote:
Originally Posted by Yzracer63 View Post
Correct me if i'm wrong, but shouldn't the generator and all gas appliances be able to run at the same time? As it sits, I can have the generator running along with the fridge, and all 3 burners on stove at the same time, but no heater. as soon as i shut the generator off the heater will fire up first try.
Yes the regulator I put on up at the tanks was one of those mr. heater automatic change regulators for dual tanks. I unscrewed the big plastic plug below the switching lever on the front and noticed there is a screw to adjust spring pressure inside but haven't touched it yet. would anyone happen to know if these regulators are adjustable? maybe it is set too low to run the generator and the heater at the same time?
Yes, you should be able to run the generator and all the appliances at the same time - it sounds like the regulator you put on doesn't have the flow capacity to supply enough propane to do that. Note that there are two different things involved here - the system PRESSURE should be 11 inches water column ( about 4/10 psi) regardless of how much VOLUME of gas is being used. If the regulator can't supply enough to keep up, you need a different regulator, not a pressure adjustment. If the regulator you put on was a 'mr heater' regulator, I suspect it's only made with enough capacity for one heater.
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Old 11-19-2018, 11:40:21 PM
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Default Re: Onan 2.5 kv spec. D wont start when hot

is there any in particular regulator you could recommend? The only ones i can find locally are the same one i got at camping world.
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Old 11-20-2018, 02:37:06 AM
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Default Re: Onan 2.5 kv spec. D wont start when hot

Camping World website lists several different ones, so not sure which you got - but the standard ones are 210,000 btuh capacity while the 'high capacity' ones are 400,000 btuh capacity, and not very much more expensive. Your genset is spec'd at .55 gph full load, which is about 50,000 btuh - so the standard SHOULD be enough if working correctly - but given your problems, I'd definitely go for one of the 'high capacity' models.
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Old 11-20-2018, 11:02:56 AM
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Default Re: Onan 2.5 kv spec. D wont start when hot

Yes i just looked on their website as well and it looks like the one i have is offered in 160000 btu and there is another identical one that is 325000 btu. They are literally identical in the photos and even have the same part number printed on the housing. I wonder if I have the 160000 btu model? I will go out today and try and get my hands on a higher btu model and try it out.
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Old 11-20-2018, 10:54:44 PM
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Default Re: Onan 2.5 kv spec. D wont start when hot

OK, Today i picked up a 400,000 BTU dual stage regulator and installed it. Nothing has changed. everything still acts the same way. I took the gas valve and burner assembly out of the heater to clean and inspect but it all checked out good. The orifice was free of obstructions and nothing is plugged up. Would it be possible that when onan is running and producing A/C power that is throwing something off electrically with the heater? also I upgraded the circuit board in the heater last year with a dinosaur circuit board. possibly something is wired wrong? I would just find that weird because it all works fine individually and they both run at same time as long as heater is running first.
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Old 11-21-2018, 04:41:12 PM
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Default Re: Onan 2.5 kv spec. D wont start when hot

Been testing electrical system to furnace and all is checking out good. still seems propane related. There is a T in the main steel propane line, left goes to generator and right goes to the little copper line feeding heater and stove.Is it possible that the generator is pulling too much propane not allowing anything to flow to the right into the smaller line? the stove starts fine though when onan is running...any advice or ideas would be much appreciated, Thanks.
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Old 11-22-2018, 12:17:16 AM
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Default Re: Onan 2.5 kv spec. D wont start when hot

Update. not sure how accurate it is but I hooked my manometer gauge to the test port on the gas valve on the furnace and with the heater running it read 9.5 to 10 W.C. and then i started the onan and my test gauge dropped to about 5 W.C. I then started turning the adjustment screw on my new regulator in one turn at a time until it bottomed out. the end pressure was about 9.75 W.C. with heater and onan running and then as i turned the three burners on stove on it dropped down as expected.
NOW with just the heater running the gauge is reading 14-15 W.C.
do you guys think all of this sounds ok?
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Old 11-22-2018, 05:10:53 PM
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Default Re: Onan 2.5 kv spec. D wont start when hot

anybody?
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