Carburator issue with video...

[95Bounder32]

I have an Onan Marquis 7000 generator that was working fine until I went to start it one day and nothing. After some major research and diagnostics, I determined that it was a faulty control board. The symptom was that when I pressed the start button, all I would get would be a clicking noise which I discovered was the sound of the fuel pump. The starter was dead and the engine wouldn't turn over. Nothing. Just the fuel pump clicking noise. After research, I was able to bypass the control board and starting relay by using a jumper wire between the battery side of the relay and the shunt coil terminal which allowed the starter to engage. This pointed toward the control board as the culprit, and it was. After I installed the new board, I pressed the start button and it fired right up and ran for about 15 seconds and then shut down. I tried pressing the start button again and all it would do is turn over and dump fuel out of the air box. I waited a couple of days and tried and it fired up and then died after about 15 seconds and dumped fuel. Same thing as before. Here is a video. Does anyone think the float is stuck open or something? And if so, is there an easy way to loosen it without removing the carb? (I don't own any stubby open/boxed end wrenches which are required to loosen the carb nuts.) TIA!

https://youtu.be/uA3MpYwGFIs

[twinboat]

You the float is stuck, sunk or debris is in the neddle valve.

If you can, drop the bowl and take a look. Its held with a bolt under the center if it.

[95Bounder32]

Originally Posted by twinboat

You the float is stuck, sunk or debris is in the neddle valve.

If you can, drop the bowl and take a look. Its held with a bolt under the center if it.

I found a picture of a similar carb on another forum. See how the brass is recessed? If I pry on the fin "A" to get it out of the groove "B", do you think it will unscrew?

[TQ60]

Harbor freight is cheap tools....buy some

[95Bounder32]

I bought some racheting stubbies from Harbor Freight yesterday. Just need the time to work on the genny. I'll be sure to post findings...

[95Bounder32]

I removed the carb and opened it up. The needle looked pristine, the float action was just fine, the bowl was very clean. I disassembled the float and cleaned all ports. I put it back together and reinstalled it. The generator started up no problem and purred like a kitten... For about 30 seconds and then died. Tried to restart it and voila... the SAME THING! Any ideas folks? Is the pressure too high causing the needle to unseat?

[twinboat]

Did you hold the carb upside down and see if the float sat level ?

If it sits to high, it doesn't shut the gas off at the proper level.

[95Bounder32]

Yes, and yes. I had the carb upside down and the float was sitting below horizontal (too high if the carb was right side up) but when I tightened the screw which holds the "pivot" rod in place, it leveled out. Then I held it right side up and raised and lowered it with my finger and the action was smooth...

[twinboat]

Last test, hold it upside down and see if you can blow thru a line connected to it. Shouldn't be able to.

If you can, you need a new neddle valve.

[95Bounder32]

Okay, I'll give that a shot in the next few days and will let you know. Unfortunately, for me, if it is the needle valve I'll have to buy a whole new carb.

[Forkyfork]

Do these carbs have a rubber diaphragm? Did you replace the needle? Ive had a similar issue with outboard carbs and after replacing all the rubber in the carb including the needle it resolved the issue. On my Evinrude the rubber diaphragm is a continual issue and I end up replacing it every other year. Pretty sure the heat contributes to the problem.

There is also a way to check to make sure the float is still floating as it should. they can get "water logged" and not float properly.

I usually buy a carb rebuild kit and throw all the parts in the kit at the issue. If cleaning doesn't resolve the issue and it isnt fuel pump or filter related. If that doesn't resolve it then I start looking at other rubber parts and seals including fuel lines.

I also worked on a motorcycle that someone had put in a lawnmower fuel filter that couldn't keep up. It would run for a bit and then starve after it emptied the filter and the filter didn't flow with enough volume. This system had no fuel pump.

[Chief Alen]

Low oil sensor maybe.

[10EC]

Originally Posted by 95bounder32

i removed the carb and opened it up. The needle looked pristine, the float action was just fine, the bowl was very clean. I disassembled the float and cleaned all ports. I put it back together and reinstalled it. The generator started up no problem and purred like a kitten... For about 30 seconds and then died. Tried to restart it and voila... The same thing! Any ideas folks? Is the pressure too high causing the needle to unseat?

i think-- the float pushes the needle up to the needle seat. high fuel pressure would only seal it tighter. i would think you have a bad needle or possible the seat is bad. May be dirt/ trash between the needle and the seat. Also try removing the float and place it in pan of gas to see if it will actually float up to seat the needle.

If this part is not avabile to you, sometimes you can match up needles from lawn mower carbs.
Bad needles are very hard to see with the naked eye.
Good luck

[10EC]

Originally Posted by 95bounder32

yes, and yes. I had the carb upside down and the float was sitting below horizontal (too high if the carb was right side up) but when i tightened the screw which holds the "pivot" rod in place, it leveled out. Then i held it right side up and raised and lowered it with my finger and the action was smooth...

this should not have been loose, unless you did it. Look closer for bent bin, or other problem there.