5.0GL-H Idle Mixture Screw Troubles

[bmies]

I've got a 2007 Larson with the 5.0GL-H. It has a Holley 2300 2bbl carb (stamped 75030).

I have the carb torn down for a full rebuild after the accelerator pump diaphragm failed, and it started dumping fuel onto the manifold. Instead of just replacing the diaphragm, I figured I'd rebuild the whole thing as I've been having some hard starting issues as well.

What I can't seem to figure out is access to the idle mixture screws. I know there should be one on each side of the metering body, and I know on some models they are covered by plastic caps. On this one though, those plastic caps seem to be blocked by tiny 'detents' in the aluminum casting on the metering body. I can't get at them. Its like someone wanted me to not be able to access the mixture screws? Anybody else have this problem? :facepalm:

 

[skydiveD30571]

Re: 5.0GL-H Idle Mixture Screw Troubles

Yep same thing. Those are metal caps that are pressed in the hole where you would normally access the idle mixture screw. It's my understanding that they are there for emissions reasons, so that you cannot richen the mixture.

Anyway, to get to mine I just simply drilled out the cap. I found a drill bit just slightly smaller in diameter than the cap and drilled a hole in it so that I could stick a screwdriver in and adjust the screw.

 

[Don S]

Re: 5.0GL-H Idle Mixture Screw Troubles

I've always had good luck using a wood chisel next to the carb body and just a tap with a hammer and they pop out.

 

[bmies]

Re: 5.0GL-H Idle Mixture Screw Troubles

Thanks skydive and Don. At least I'm not crazy. The metering body is already looking a bit worse for wear, so I'll try the small drill and go at it slowly.

 

[bmies]

Re: 5.0GL-H Idle Mixture Screw Troubles

Haven't drilled the mixture screw caps yet, but I did reassemble the carb with a fresh rebuild. I've got another question.

The rebuild kit came with a different accelerator pump diaphragm than what was in the carb. Its the same overall dimensions, but the metal cap in the diaphragm is different. Upon re-assembly, the accelerator pump lever arm is far from contacting the adjustable 'pump screw' with the throttle closed.

I'm new to marine carbs, but in auto world the adjustable 'pump screw' should just contact the pump lever arm at closed throttle. In order to have the bolt head of the actuator contact the arm of the accelerator pump at the throttle closed position, I had to adjust it almost half an inch longer and am at the limit of adjustment. Is this correct?