Carb running rich

Scott 'Gunny' Perdue · **Posted:** Tue May 28, 2013 6:19 am

Matt Gunsch wrote:

Scott 'Gunny' Perdue wrote:

bdk

You missed the part in my post that mentioned I have a fuel flow and an engine monitor.... I know exactly how rich the engine is running and which cylinders are not firing.... I appreciate your inputs.

At the moment the leading theory is one of the floats is cracked. That is the one I'm going with.

gunny

If you know what cylinders are not firing, why don't you let us in on which ones they are, it might help figure out what is going on.

Since the engine is supercharged, the fuel air charge should be evenly mixed before it gets to the cylinders, so there should be no lean or rich cylinders unless there is something going on with a cylinder or cylinders. You said the engine had 250 hrs, have you run the valves ? Checked the packing gland nuts on the intakes ? a leaking primer ?

Matt-

Most of the time they are 1-3, sometimes 5-6. I ran the valves two months ago as well as the packing gland nuts. I'll look at the leaking primer idea, but not sure how that would affect FF. Carb is off and headed to Aero Eng for a checkout.

gunny

bdk · **Joined:** Sun May 02, 2004 1:16 am **Posts:** 11319

Sounds like you are down to the expensive stuff now...

Matt Gunsch · **Posted:** Tue May 28, 2013 2:07 pm

cylinders 1,2,3 are primed, so a leaking primer is a better possibility, but 5 and 6 straddle the sump, and I could see them being oil fouled to the point of not firing or intermittently firing until the oil is burned off at higher power settings.

If you want to eliminate the primers, cap off those lines and see if they quit running rich.

Scott 'Gunny' Perdue · **Posted:** Tue Jun 11, 2013 6:27 am

Carb shop reports that the idle mixture valve was installed backwards.... improbable but true... allowing the fuel to leak by... doesn't really describe the intermitent problem... but..... also one of the floats was cracked with a small seep....

gunny

The Inspector · **Posted:** Tue Jun 11, 2013 10:27 am

Glad to hear at least a part of you issues have been found and corrected, it's usually the itty bitty stuff that eats your lunch-

bdk · **Joined:** Sun May 02, 2004 1:16 am **Posts:** 11319

Check out the July 2013 NATA Skylines. On P.36 it describes a condition whereby the idle cutoff plunger sticks causing intermittent mixture problems and rough running. I'm sure your carb shop has taken care of all your issues, but this could have been a possibilty too.

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Carb running rich

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