Started my 86 F250 7.5 4x4 C6 up today for the first time in a while, and everything started out fine, but then she started to chug ALOT, and eventually died. Figured it was carb related so I pulled the cleaner off, and sure enough, it was covered in gas, so something is stuck open.

I'm not too familiar with carbs, and i'll eventually be going to FI, but for the time being, gotta keep the old girl running strong.

I've heard of jets being stuck open, and needing a hammer to get them to get unstuck, but when I fired it up again to see where all the gas was coming from, I don't think it's the jets.

I've searched all over the place for the name of the tube at the front of the carb that's sticking straight up. I've circled in red where all the gas was pouring out of:



Gas was just gurgling out of that front tube, and I believe it's the secondary flap there is stuck open as well.

Anyone with carb experience....is this a quick fix or does the whole carb have to be rebuilt?

Thanks.

 

Your float needle is stuck open. It' either gummed up or has a piece of dirt in it. Couple things you can try;

Take the plastic handle of a screwdriver and peck on the top of the carb near where the fuel inlet is located. This jarring from the screwdriver handle will sometimes break the needle loose.

If you happen to have a rubber hose feeding the carb ( a lot of the factory setups are metal line) you can get it running and pinch the line shut. The engine will smooth out and run for a little bit, and then as the fuel starts running out in the carb, you can quickly let up on the fuel line and the fuel rushing into the carb will dislodge any dirt holding the needle open.

This works just like the bowl on your toilet. You have a pressurized line coming into the carb from the pump (just like the toilet water line from the house) and you have a float and a needle valve with a fuel reservoir inside the carb that keeps the reservoir at the correct level, just like the toilet has a water reservoir in the back of it.

 

I've seen that done before, so i'll give that a try.

What is the name of that tube though? Float?

 

That tube is the breather for the fuel bowl or reservoir. Just like your toilet tank lid has places in it where the lid does not fit tight. As the fuel comes in, the air has to go somewhere, it comes out of that tube. When there is too much fuel the fuel rushes out of that tube, and also through some passages down into the engine, which floods the engine out.

 

P.S. If you are going to let this truck sit around a lot, you would be better served putting non-ethanol fuel in it. It's a little more expensive, but it will help eliminate these problems. Either that, or keep some Stabil in it.

 

I've only ever ran non-oxy in it since I got it. Learned my lesson the hard way with mowers and weed whackers over the years. The PO however did not get the memo, and the secondaries were completely gummed up before I had it rebuilt:

 

Must be a piece of dirt under the needle. Do the peck with a screwdriver handle method and see if it clears up.

 

The problem with secondaries is the fuel sits there even if using the truck. You have to open the secondaries once in a wile to move the fuel out of the bowl.
Dave ----

 

Holley designed their carbs so the secondaries contribute a small amount of fuel at all times just for that reason, so if Grandma drives the vehicle the fuel in the secondaries doesn't go stale.

 

Air Vent & really Nasty Carb!
Holley FLOAT has adsorbed fuel into the supposedly fuel resistant plastic material used to make it buoyant; age-time in fuel seems to affect some of the float problems, particularly when the Alcohol Methanol/Ethanol Blends arrived in the fuel market. IMHO - I think some brands of fuel additives are too caustic, & can be over used in their concentrations and will cause damage to some NON-Metallic parts over time in using them. Seems this could cause some carb floats to absorb fuel & sink Causing flooding into the carb via the air bleed tubes & venting ports - to the point it would sometimes not start, backfire and catch fire. Most fuel systems supply was with one-way fuel valves, diaphragm attached to a mechanical pivot arm driven by the cam shaft lobe.

Holly carbs sometimes have issues with fuel system trash on its needle&seat causing no shut off of fuel flow resulting in over fueling and poor or no idle because fuel is overflowing into intake while engine is running. Engine runs erratic as fuel spills out of air bleed ports above the throttle baffle plate butterflies. You can hear the fuels spurts & surging in carb air intake. As The fuel float cannot shut-off the fuel supply to maintain the correct fuel level in the carb fuel bowl. A good inline filter should be installed, if you don’t have one.

The Holly Fuel float level may be too high if no trash is stuck in needle& seat. This will cause a fuel over-flow through air bleed hole/orifices in venture above throttle plates.

 

Rebuild that Sludged Chocked carb!

 

You must have missed it, he has already rebuilt it previously, those are older pictures.

 

 

That is a good point. You can see the needle assembly in the picture below, it's behind the light brown plastic piece. You can take that large flat screwdriver headed screw loose, and then turn the large nut and back the whole assembly out and take it out of the carb and inspect it. Make sure to put a little oil on the o-rings before you put it back in place. And then you will have to reset the float level, there should be a site plug on the side of the carb, the fuel level should be at the bottom of the hole.

 

See, now its getting to the point where I start to go cross-eyed, and my nose starts to bleed, because i've never done half of that stuff.

Take the carb off the truck? No problem.

Hit the front with a screwdriver to hopefully dislodge a stuck needle? Easy peasy.

Tear the carb apart and start setting float levels?!?