Remove primer

Gang,

I'm trying to troubleshoot a couple of fuel metering problems. The first problem is idle-cutoff doesn't actually cutoff. Recently, I've needed to use the ignition to kill the engine. Also, if I advance the throttle rapidly (faster than about 3 seconds) the engine stumbles. It eventually recovers, but it's clearly an issue. I've done some searching through the forums and I've come across several threads where people had similar symptoms and a common suggestion is disconnecting the primer to make sure it isn't leaking.

I'm not sure how to safely do that. I have an electric priming system. The fuel comes out of the fuel line just before entering the carburetor and enters the primer solenoid. It goes out the other side of the solenoid and tees off to two cylinders. Can I just plug the line that feeds the solenoid or do I need to disconnect the priming ports at the cylinders as well?

Personally, I would remove the primer alltogether. I live in Wisconsin and never needed a primer to cold start my 0-360. If you leave it on to test for leakage, I would plug all openings you make to isolate the system. I would also make sure the float level is correct on the carb and make sure the needle and seat aren't leaking. Make sure the linkage that closes the idle cutoff is properly adjusted to ensure complete closing. Make sure you have the carb adjusted properly to see about a 50 rpm rise just before idle cutoff kicks in. These suggestions aren't necessarily in order. Try doing the simplist things first. But do the carb mixture adjustment after you have resolved the idle cutoff issue. A too rich or lean carb adjustment can cause engine stumbling. You do not state what engine. An 0-360 will have an accellerator pump in the carb where an 0-320 will not. The accellerator pump assists in faster accelleration of the motor in revup.

Roberta

Thanks Roberta. I have an O-320-E3D. Thanks for the suggestions. It sounds a bit more complicated than I though and I will enlist the help of someone more knowledgeable than I to cover your list. I didn't build the plane and I just don't feel comfortable messing with the fuel system.

320 carbs do have accelerator pumps and I agree with removing the primer system and use the accelerator pump for priming just like they do in a Mooney.