Merc 3.0 won't run with choke open

[mudcat88]

Okay I have a 2000 bayliner with a mercruiser 3.0 engine. The problem that I am having is that the engine starts and idles fine as long as the choke plate is closed. Once the auto choke opens to about halfway the engine sputters and dies indicating to me a lean condition. The only way to start the engine once the choke opens is to move the throttle to WOT and even then it will not keep running.


After the problem started I had the carb rebuilt/cleaned by a local merc dealer and I have tried starting the engine from an auxillary gas tank with clean fresh fuel however the problem persists. I am at my wits end and really could use some help.

 

[Bondo]

Re: Merc 3.0 won't run with choke open

After the problem started I had the carb rebuilt/cleaned by a local merc dealer

Ayuh,... Welcome Aboard,... What did He say when ya told 'im it still don't run right,..??

 

[EddiePetty]

Re: Merc 3.0 won't run with choke open

...after the choke has opened and the ignition points are open, measure the voltage (key ON) at the + terminal of the coil to ground. I am suspecting that the resistance wire is too...well, resistive and/or it is creating an open.

 

[Don S]

Re: Merc 3.0 won't run with choke open

...after the choke has opened and the ignition points are open, measure the voltage (key ON) at the + terminal of the coil to ground.

Points weren't used in 2000, nor a resisrance wire.
Sounds a lot like you have a vacuum leak. Get some spray carb cleaner, or parts cleaner, and spray around the carb basew and intake manifold gasket to head and see if you hear the engine change rpm.

 

[mudcat88]

Re: Merc 3.0 won't run with choke open

I will try the vacuum leak test and see what it turns up. I took the carb off to have it rebuilt and I replaced the mounting gasket when I bolted it back on so I think we can rule out that gasket especially since it is acting the same prior to and after the carb rebuild.

So if the vacuum leak test comes up negative then I guess it is back to the shop to have them re-rebuild the carb.

 

[fishrdan]

Re: Merc 3.0 won't run with choke open

Have you adjusted the idle speed and idle mixture screws?

 

[mudcat88]

Re: Merc 3.0 won't run with choke open

Okay, the vacuum test came negative...that is good news since I didn't feel like tearing apart the manifold.
Good news is I think I found the problem. I put a primer bulb in between the the gas tank and the fuel pump and squeezed it while opening the choke fully and I was able to keep the engine from dieing. Looks like I need to change out the fuel pump.