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jpatt87 · 05-29-2018, 04:15 PM

The 4000 onan in my 1992 bounder is having issues. It has been running rough since we started this yr. I cleaned carb and installed a new low pressure fuel pump..
2 things I'm not sure about.
The screw with the spring on the bottom of the float bowl. Do I make it tight against the spring or does it matter. I read that that was an adjustment and not a drain like I thought.
And 2... The round thing behind the plastic cover that has 2 wires going to it and it says lean/rich on it. It turns left or right.. I played with that and not sure where it needs to be. I cant even find a picture of one online to compare my adjustment to. Also the generator black smokes a little. Any help would be great

Mr_D · 05-29-2018, 04:20 PM

Brand and model of the generator would help so we don't have to guess.

jpatt87 · 05-29-2018, 04:24 PM

it just says onan emerald plus
model number 4bgefa26100j

twinboat · 05-29-2018, 04:35 PM

The screw with spring is a mixture adjustment. Start with 2 turns out from snug. Start the engine, let it warm up for 5 minutes, then slowly turn it, in or out, to where the engine runs smooth. Do it with some electric stuff on.

The rich / lean thing is the choke adjustment. Set it so the choke butterfly is fully open after 2 or 3 minutes of running. The choke butterfly is the round valve just behind the air filter.

Do the choke adjustment before adjusting the mixture screw. The choke must be fully open.

wiredgeorge · 05-29-2018, 04:47 PM

Quote:

Originally Posted by jpatt87

The 4000 onan in my 1992 bounder is having issues. It has been running rough since we started this yr. I cleaned carb and installed a new low pressure fuel pump..
2 things I'm not sure about.
The screw with the spring on the bottom of the float bowl. Do I make it tight against the spring or does it matter. I read that that was an adjustment and not a drain like I thought.
And 2... The round thing behind the plastic cover that has 2 wires going to it and it says lean/rich on it. It turns left or right.. I played with that and not sure where it needs to be. I cant even find a picture of one online to compare my adjustment to. Also the generator black smokes a little. Any help would be great

I rebuild and sell vintage Japanese motorcycle carburetors for a living. The screw you refer to with the spring around it is the mixture screw. It fits into what appears to be the main jet. If the main jet sits on the bottom of the bowl, you can pull it out and stick a fine piece of wire through the holes and spray it with carb cleaner if the gas in the bowl got gummed up a bit. I have to do this about every other time I try to start my lawn mower as it also has the fuel jet sitting on the bottom of the bowl where it is most likely to get gummed up some. If I don't start the mower for a month or more (summer in Texas means grass doesn't grow fast), the cleaning is a start-the-mower ritual that can't be avoided unless I spent the money on ethanol free gas which I do use in my weed trimmer but not the mower. As far as the screw goes, it will be sharp on the end and you want to very very lightly want to turn it in (clockwise) till it just touches as I suspect the end can break off easily) then turn it out 2 turns... just guessing. Might be a good idea to lightly seat it and count how many turns it is now to go back to that setting.

jpatt87 · 05-29-2018, 06:05 PM

Quote:

Originally Posted by twinboat

The screw with spring is a mixture adjustment. Start with 2 turns out from snug. Start the engine, let it warm up for 5 minutes, then slowly turn it, in or out, to where the engine runs smooth. Do it with some electric stuff on.

The rich / lean thing is the choke adjustment. Set it so the choke butterfly is fully open after 2 or 3 minutes of running. The choke butterfly is the round valve just behind the air filter.

Do the choke adjustment before adjusting the mixture screw. The choke must be fully open.

We are talking about the spring on the very bottom of the float bowl of carb right, and not the screw at the top. I know the one on the top is a mixture screw. It is about 2 turns out... I'm meaning the one on the float bowl bottom

jpatt87 · 05-29-2018, 06:08 PM

I got it running a little bit ago. So then I turned on the ac and it bogged down a lot. Then dies roughly after 40 seconds or so with ac running. I noticed I'm getting close to 1/4 tank of fuel now so I stopped and will put gas in it tomorrow as I was told they wont run at 1/4 tank. Don't want to be trying to tune it if its just not getting enough fuel.

twinboat · 05-29-2018, 07:39 PM

Quote:

Originally Posted by jpatt87

We are talking about the spring on the very bottom of the float bowl of carb right, and not the screw at the top. I know the one on the top is a mixture screw. It is about 2 turns out... I'm meaning the one on the float bowl bottom

Yes the one on top, side is the low speed adjustment. On the bottom is the high speed adjustment.

jpatt87 · 05-30-2018, 02:18 PM

ok so I got it running good. It idles and has 128-130 volts with the tv on in the rv. Turn the fridge on and it drops to 117-118. Now with only the tv on and then I turn on the roof top A/C then it drops to 98-99 volts and then after about 50 seconds it will die very roughly. I just ran the ac all last weekend for 3 days and it never died. That was before I messed with the lean/rich thing but since that is for the choak then it should not matter right?
Am I missing something? Also the gold idle mixture screw on the very top of the carb does nothing to it. So it is 1.5 turns out from snug. But why all of a sudden does the voltage go away and then it die when I turn on high A/C

twinboat · 05-30-2018, 02:28 PM

The main jet could be clogged or its not getting enough gas into the carburator to run while under load. Fuel pump or gas filter.

It should be holding a steady engine speed and voltage when running. Around 120 volts is what your looking for.

The throttle linkage from the carb goes to a engine speed governor. If that's been messed with or sticking, the throttle plate will not move properly. The engine never idles, it always turns the same speed, but just works harder, when added loads are put on the generator.

jpatt87 · 05-30-2018, 03:29 PM

I did some more adjustments and got it to run while the A/C is on. It idles at around 125 volts with the tv on and then when I turn on high AC along with the tv it drops to 97-5-98.9 and stayes there. Nothing I do can make it better. if I tighten the screw on bottom of the bowl then voltage will drop and then eventually die. If I lossen it then the voltage just drops but it stayes running. The screw that touches the throttle linkage that points down can make it idle higher and give more voltage but the linkage is not even close to it anymore when AC is turned on. Also the rod that runs from that to the top of the engine speed govenor has a slight end to it. Maybe that is not soppose to be bent? Also I cannot run the fridge at the same time as the AC. It says A4 code on fridge and wont start which is no voltage to fridge. We run it on propane so I don't mind that I guess. Could the AC have a issue that is causing the voltage to drop

jpatt87 · 06-06-2018, 04:29 AM

So i have tested the ac on other generators and everything is fine. I tried mine last friday and it was perfect. 125 volts with no load and then 125 volts with it on high ac. I thought it was fixed and good to go. Tried it the very next day and every day since then and it has not been good. 125 with no load and 100 volts with ac on. Is this a governor issue or still carb related