Help! Old onan generator problem

[hpbcrillo]

Hello, I have a 83 hr alumalite 30' class A, and the generator ran fine a few months ago. now it won't run unless you pour gas into the top of the carburetor. There is plenty of fuel flowing out of the fuel pump into the carb, but none getting into the venturi. I took the carb off and used carburetor cleaner on all the ports, etc. Took it apart and the floats are working, the bowl was full of fuel but none getting into the engine. After cleaning it thoroughly and blowing compressed air into all the ports, it seems that the blockage is gone. HOWEVER....I turned out the star shaped 'valve' (see picture) until it was clear of it's seat....and I don't know the proper adjustment of it. IT looks like it meters the flow of fuel from the bowl into the venturi? But how many turns out should it be?
If you can help I would be incredibly grateful....and Thank you to all who respond!

[NHRA225]

Looks like an older CCK Carburetor- I would start with 1 1/2 to 2 turns from fully closed and final adjust from there.

[TQ60]

That looks more like a float bowl drain as the adjustment p@part is usually vertical but this could be different, if a drain it will dump fuel and not effect running until it dumps fuel.

Assuming you confirmed it is an adjustment then generic process follows.

Those can be tricky but as above...

Most of all carb adjustments seem to always start at 1.5 turns...Universal starting place.

General instructions.

Disconnect throttle linkage to governor and unplug or turn off power output connection.

Locate idle adjustment screw and set to 2.5 turns.

Locate idle speed screw and turn until throttle "just opens".

Start engine and first adjust throttle speed to a low idle and allow it to warm up.

Next adjust idle mix for best running.

Reduce idle speed and repeat.

Once it is idling good manually increase throttle to mid speed and return to idle.

Basically goose it.

Adjust screw in photo a little but and repeat until it runs smooth from idle to more speed.

This will impact idle mix so repeat both.

When finished reconnect throttle linkage and restart.

Adjust the above for best operation and it should only be minor.

Reconnect power and turn on all ac and lights for a load test.

If the above is out of adjustment it will not have good power under load.

[hpbcrillo]

Originally Posted by TQ60

That looks more like a float bowl drain as the adjustment p@part is usually vertical but this could be different, if a drain it will dump fuel and not effect running until it dumps fuel.

Assuming you confirmed it is an adjustment then generic process follows.

Those can be tricky but as above...

Most of all carb adjustments seem to always start at 1.5 turns...Universal starting place.

General instructions.

Disconnect throttle linkage to governor and unplug or turn off power output connection.

Locate idle adjustment screw and set to 2.5 turns.

Locate idle speed screw and turn until throttle "just opens".

Start engine and first adjust throttle speed to a low idle and allow it to warm up.

Next adjust idle mix for best running.

Reduce idle speed and repeat.

Once it is idling good manually increase throttle to mid speed and return to idle.

Basically goose it.

Adjust screw in photo a little but and repeat until it runs smooth from idle to more speed.

This will impact idle mix so repeat both.

When finished reconnect throttle linkage and restart.

Adjust the above for best operation and it should only be minor.

Reconnect power and turn on all ac and lights for a load test.

If the above is out of adjustment it will not have good power under load.

Thank you, I found a manual on the internet and it is the valve to control the flow of fuel from the float bowl into the rest of the carb....and it said to turn it out 1.5 turns to start. I did that, put the carb back on and the generator runs! It starts out very smooth, but as it warms up it starts to 'hunt', sputter and occasionally backfire.
I will try the tuning method you outlined and see if that helps.
Is the idle speed adjustment the screw that the governor linkage rests on?
thank you again! Will let you know how it turns out.

[TQ60]

The idle speed is the screw that the throttle rests on.

You need to disconnect the linkage to the governor so the engine will run without other control.

Been adjusting small engines for many years and it is easy but it does take a bit of time and a bit of repeat motion to get it good.

If there is a place to hook up a vacuum gage even better.

[Geocritter]

In the future, if you're going to take a carburetor apart it's a good idea, before you unscrew the jets, to screw them all the ways in to their seats, counting the turns. Then mark that number on a piece of scratch paper so that you have it when you put the carburetor back together.


Steve


PS don't be embarrassed if you forget that first step, its an easy thing to do.

[ahicks]

That "hunting" is often caused by a lean mixture. I would turn your adjusting screw 1/4 turn counter clockwise to see if that improves it.

[hpbcrillo]

Originally Posted by Geocritter

In the future, if you're going to take a carburetor apart it's a good idea, before you unscrew the jets, to screw them all the ways in to their seats, counting the turns. Then mark that number on a piece of scratch paper so that you have it when you put the carburetor back together.


Steve

Thank you, I watched a video before I took it apart and did remember to do that. It helps!

[hpbcrillo]

Originally Posted by ahicks

That "hunting" is often caused by a lean mixture. I would turn your adjusting screw 1/4 turn counter clockwise to see if that improves it.

Thank you, I will try that. Have been out of town all week so got to start working on it again tomorrow!

[ROLLNSMOKE]

Only way to get it right is to pull the carb completely apart, clean, pressure test the needle and seat to make sure it seals and reassemble. Blow out all the orfices with compressed air.

[Geocritter]

Also, if you're going to take apart and clean the carburetor get a can of carburetor spray cleaner equipped with one of those long red tubes. With that red tube you can get a power spray way down into passages where crud can collect. I wish they'd had those setups when I was a teenager working on old beater cars!

Steve

[udid]

And once everything is running peachy prior to storing the RV pour into the fuel tank the proper amount of fuel stabilizer (STA-BIL) and top the fuel tank off. Once that is done run the engine and generator for 10-20 mins.

This will ensure the fuel does not turn to varnish and plug up carb orfices. It will also absorb water in the tank or bowls. Allowing for the generator to start after long storage.

[TQ60]

Has anyone thought about adding a switch to the electric fuel pump or a valve to the fuel line to allow for shutting fuel supply off ?

This would allow one to fun the genny dry to reduce chances of aged fuel in the carb.

May be benefit for extended storage.