random flooding

[Bitzer!]

So, with the flexiplate sorted the truck throws another curveball at me.

When it starts it'll idle nicely in neutral for appx 20 seconds then fuel will come out of the vent looking tube by the choke flaps. No gas pedal being touched. When a gear is selected it just drowns itself and will stall.

The carb (750 Holley) was rebuilt 4 months ago and the whole unit dyno'd and set up correctly. The garage rebuilt the carb.

Cleaned out the needle valve at the front, couldn't see any dirt debris there.

Where should I start looking next!

Cheers

Andy

(I will get to drive this truck properly one day!!)

[80Chevy4x4]

I would start by making sure your float in the carb is working properly and adjust properly....definitely sounds like something along that caliber....I had that problem before.

[bd]

With all those curve balls you need a BIGGER MITT!!!

Remove the bowl cover.  Inspect the way in which the needle valve is "hooked" to the float.  Make sure the needle isn't hooked through one of the holes of the float.  The hook should slip onto the float from the front.  Make sure the float hinge is properly installed in the carburetor body, not reversed end-for-end; it should be a stable anchor for the float.  Make sure the float swings freely on its hinge without binding or dragging against other items in the bowl.

Now, "pop" the power piston (with its suspended metering rods) loose and remove the piston and float from the bowl.  Inspect the manner in which the rods are suspended from the power piston and the dampening spring that embraces the rods.  No need to take it apart, just look at it, so you can reinstall it correctly.  Gently towel the float off.  Give the float a squeeze and see if it oozes fuel.  Replace it if it does. 

While the float is out remove the needle valve, fuel line and filter.  Blow the fuel inlet area of the carburetor thoroughly clean with compressed air.  Make sure there is no debris lurking about.  Verify that the needle valve seat was installed with a gasket and that the seat is appropriately tight.  Inspect the "soft end" of the needle valve for cuts or distortion and replace if questionable.

Reinstall the needle valve and float.  Check and adjust the float level to spec using an adjustable "T" gauge (a kind of double sliding ruler).  Carefully reinstall the power piston making sure the rods enter the jets in the floor of the bowl without bending.  Make sure the dampening spring properly engages the hanger end of the rods.

Reinstall the filter, inlet nut and fuel line.  Use a gauge and verify that the fuel pressure is 5-7 PSI.  Make corrections as needed.  That about sums it up.

[Bitzer!]

Cheers bd, that's pretty comprehensive. Maybe I didn't go far enough with the investigating.

Pop the piston is new to me. Is that pop it out or make it work?

I know I sound a donut but I weld/paint and usually leave these bits to others!

[Fairlane514]

Hey Rich,

I think he said he has a Holley, you were describing a Quadrajet!     

On the Holley, its possible the floats or one float has a leak in it and it has become filled with fuel and can no longer float and shut off the fuel. Take the float bowls off, remove the floats and shake it to hear for fuel if its brass. If its black rubber then it may just be soaked a too heavy.  See if it floats in some water

[Bitzer!]

Don't confuse me- I'm bad enough already!

Floats are mint. When the carb was rebuilt they resoldered one of them, I've checked again for good measure but they're both fine.
 
And yes it's a Holley 750

Next?

Andy

[Fairlane514]

The only thing that would cause spilling fuel out of the vent tube is too much fuel in the bowl. Could also be a fuel pump over powering the needle and seat. Should have 5-7 psi.

So the Holley floats are new? They typically don't come in a rebuild kit.

[bd]

Ooopps!   Sorry Andy.  Another curve ball it seems!  I really wasn't intending to do that.  I'm gonna chock it up to the heat.  It's only around 108° here today, but apparently that was hot enough to cook me 'ead.      Fairlane is correct - I comprehensively described the wrong carburetor....  So, if you manage to fix it based on my lead you're a pretty accomplished guy! 

To augment Fairlane's posts, on a "HOLLEY" the principle is the same and the process is similar (except for the power piston and metering rods).  Make sure the float swings freely, isn't heavy, and no debris is hiding in the needle & seat.  The float level on most Holley 4-bbl's is adjusted from the outside with a screwdriver and 5/8" box, so that fuel is at the very bottom of the float bowl fuel level sight hole with the brass plug removed.  If it's a single inlet carburetor, there's a fuel level equalizing tube between the secondary and primary bowls, so be sure the secondary float level is set correctly as well as the primary.  Also check to see if the dampening springs are present if you have side-hung floats. 

All things considered, Fairlane pretty well summed it up in his last post.

[Bitzer!]

Haha BD- I have tried confused.com and your name came up!
Seriously though I'll rip apart the fuel bowl and double check everything. Twin inlet but only floods one side, mechanical fuel pump too so nothing fancy.

Bizarre it's only just started doing it after sorting the flexiplate issue!

Ta stars

Andy

[bd]

     ...Were that my only confusion, I'd be one happy Bear!

Back to benefiting the needy....

Side- or center-hung floats?  On rare occasion, a side-hung float hinge pin will work loose from the bowl causing the float to drag.  Typically, a little red Loctite or epoxy will re-anchor the pin. 

As Fairlane suggested, a needle valve not controlling the fuel entering the bowl is the cause.  Trash in the seat is probably the best bet.

...Bizarre it's only just started doing it after sorting the flexiplate issue!

Maybe you got one of the bolts too tight.   

Cheers

[Bitzer!]

cheers guys, life has been a little manic over here AND we've had some warm weather for once so it'd be rude not to take advantage!

The floats are side hung so looks like I need to do some more investigamating.

...Bizarre it's only just started doing it after sorting the flexiplate issue!

Maybe you got one of the bolts too tight.   

Cheers

It probably didn't like me being right!

Update later..........cheers all