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Mercury 9.9 starting issues

U

Ue3

New member
Hello, I have a 2007 mercury 9.9 4stroke pull start tiller motor.it sat for about two years but ran great when it iwas parked.tried to get it running with no luck. I rebuilt the carb with genuine mercury rebuild kit. I replaced the coil with new one and new plugs too. I can get it to start with starting fluid and about 20 pulls on the rope.when I hook up the gas tank it floods instantly.i replaced the float with the one that came in the rebuild kit.so I decided to put the old float in and seams to work fine but when I put the carb back on and hook up the tank it floods again. I can only get it to start with the starting fluid and the gas tank not hooked up.any help will be greatly appreciated.thank you in advance
 
If the float "floats" in a fluid, it's typically good and no need to change it. Shake it and if it's empty, its probably fine. If it has any fluid inside, trash it.
The following is basic and I don't want to insult you but maybe a refresher would help. Fuel comes into the carb float bowl from the fuel pump or gravity via the needle and seat. When you first start the engine, assume the float level is down and the needle & seat are open. As fuel flows into the bowl the buoyancy of the float pushes the needle UP and shuts off the fuel. It's as simple as that.

Now if the needle's seating surface is pitted, marred or otherwise not closing properly the level of fuel will continue to rise which can lead to flooding where the fuel runs into the engine and the mixture is too rich to fire. Check your plugs, if they are wet it's getting fuel.
Same thing with Float Level being set wrong (too high), again the fuel flows over into the engine and makes it too rich. If it's too low the engine may not reach maximum speed but it doesn't sound like that's your problem. In your case they are probably dry. Bottom line, regardless of which float you use, the float level has to be correct so be sure to set it according to the repair kit's instructions or a manual.

Once the engine is running, or turning over quickly, the vacuum created at the narrowest part of the carb, sucks fuel from the bowl via the tiny passage(s) or pipe that is exposed to that vacuum and reaches the fuel. If your engine is trying to start I'll assume you have spark so that leaves timing and fuel flow. Since it wasn't disturbed while sitting I would say the timing is fine.
Fuel flow is probably where your problem is. You need to make sure the path the fuel takes from the bowl to the venturi in the carb throat- that necked down area) and into the engine is clear and open. Take it apart and squirt carb cleaner through the various passages and watch where the they go to be sure they are open. Then when reassembling it, make sure the float level is correct, and the float and needle move freely.
Other areas to check are the carb to engine gasket since leaking there will deplete the vacuum and there will be nothing to PULL fuel into the engine.
Good luck
 
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