'02 Merc 3.3 starts but won't run

[timjet]

Hi Folks,
My '02 Merc 3.3 HP starts easily after sitting awhile but won't continue to run after about 10 seconds. I then can't get it to start. After waiting a day or two the same thing happens, starts on the first pull, runs about 10 seconds and stops. Can't get it to start again.
The engine has in my estimation less than 50 hrs. I've always fresh water flushed it when done using and there is very little corrosion. I've always ran it dry of gas prior to storing.
I suspect the carb may need adjusting or cleaning, but before I start I'd like to get advice on how to do this. There is one carb adjustment screw. I also noticed a little gas around the top of the carb bowl specifically around the screw that holds the bowl to the carb.
Where should I start?
Thanks,
Tim

 

[achris]

Re: '02 Merc 3.3 starts but won't run

Once you've run it and it has stopped and won't re-start, have you checked for spark? You may be looking at an ignition problem. 10 seconds is a bit short for it to be the carb bowl running out of fuel.

Next time, check for spark....

Chris.......

 

[timjet]

Re: '02 Merc 3.3 starts but won't run

I started it about 30 minutes ago and it ran about 10 seconds. Can't get it to start or even fire. I checked the spark, it is still good. If I wait until tomorrow, I will get the same result, starts on first pull, runs 10 sec, stops and can't get it too start or even fire again.
I don't think it's an ignition problem, I've check the spark numerous times and it's always been good.

 

[achris]

Re: '02 Merc 3.3 starts but won't run

What happens if you choke it, does it seem flooded? Tried squirting a bit of fuel into the carb? Have you replaced the spark plug?

Chris.........

 

[timjet]

Re: '02 Merc 3.3 starts but won't run

OK, Yes I believe it could be flooded. I can now confirm there is a fuel leak that appears to be coming from the carb bowl. There are two screws holding the bowl to the carb. They are tight.
I'm not sure this is the problem, but needs to be fixed before proceeding further. Can you tell me if I simply need to remove the bowl and replace the gasket? And if so, it appears the bowl can be removed without removing the carb from the engine. Is this true, and if not how is the best way to do this. I'm pretty sure the leak is around the carb bowl as it is leaking several drops a minutes and there is no fuel elsewhere on the motor.
Thanks,
Tim

 

[timjet]

Re: '02 Merc 3.3 starts but won't run

I've found the leak. It is coming from a hole on the right side of the carb body which is hidden when the choke is open but visible when the choke is closed. I've attached a picture.

 

[achris]

Re: '02 Merc 3.3 starts but won't run

Fuel leaking from there would indicate that the float chamber is flooding, and that means the needle and seat is not closing properly. Remove carb, strip and fit new needle and seat.

 

[timjet]

Re: '02 Merc 3.3 starts but won't run

Is it necessary to remove the carb?
I understand to replace the needle, but what do you mean by strip and seat?
Thanks,
Tim

 

[achris]

Re: '02 Merc 3.3 starts but won't run

Needle and seat is the valve system that control the rate at which fuel enters the float chamber. The float controls the position of the seat. As the float rises (more fuel in the chamber) the needle closes against the seat. When fuel is used the float drops and the needle unseats and fuel flows in....

Do you need to remove the carb? Yes, but it's really easy... If you can use simple hand tools, work in a clean environment and have the manual, no problem.

Chris........

 

[timjet]

Re: '02 Merc 3.3 starts but won't run

Chris,
Thanks for staying with me on this. I think I understand.
I unscrewed the seat (the threaded fitting which houses the needle valve and is threaded into the carb body, the other end connected to the fuel line) and removed the needle valve (actually it fell out). Attached is a picture. It is obviously worn and needs replacing. Do I need to replace the seat as well?

I was able to do this without removing the carb from the engine. I didn't want to do this fearing I would have to replace the O ring if it got damaged in removal. Any way doesn't seem necessary to remove the carb at this point since I've removed the seat and needle valve.

Anyway 2 questions:
1 How did the needle valve get so damaged with less than 50 hrs on it. Wrong fuel/ fuel oil mixture? I did use premium fuel before I know better. I've always used 50:1 oil mixture.

2 Does the pointed end of the valve go down into the carb body. It fell out when I removed the seat so I'm not sure. And does the seat need replacing?

Thanks Chris for all your help.

Tim

PS: Wheres the best place to purchase parts?

 

[achris]

Re: '02 Merc 3.3 starts but won't run

That appears to be water damage

If I was you, I'd be draining the fuel tank and flushing it (and the fuel lines) and removing the carb and cleaning it out. I think you can only buy the needle and seat as a single assembly. The corrosion on that needle will also be on the seat....

A lot of engine parts here at iBoats, for anything else go to your Merc dealer.. (And have the engine serial number with you)

Download the service manual for your engine here...

http://rapidshare.com/files/213240333/2.2-2.5-3-3.rar