Hi all. I have an 85 fullsize with a 4.9L with the feedback carb.
I had a curious problem, it ran good one weekend, it sat all week, the next weekend it ran like crap. would not idle and would stall. I pulled a large vacuum hose off of the vacuum tree and the rpm came up and it idled good with out stalling.
Among other things I need to do to the bronc, like add an o2 sensor and replace a faulty egr valve (it ran ok without these 2 items), I had an extra egr spacer plate that goes between the carb and intatake, I cleaned the extra one up. I decided to swap the plates. I removed the carb and set it aside on the valve cover, left the gas line connected. I put the cleaned up plate on and bolted the carb back on, reconnected the plugs to the cpu harness. I tried starting it and it won't start. Cranks good but no start. Checked the carb and saw a light film of gas on the butterfly so I figured it was flooded. I held the gas peddle to the floor and tried again and it seemed like it was trying to start but won't. I pulled the choke pulloff hose off the bottom of the carb and there was gas on the hose.
I pulled the front spark plug wire off and used a screwdriver close to a ground to check for spark and had a good, steadt spark. I left it sit for about 2 hours then tried it again and the same thing. excess gas and no start.
Tomorrow I'm going to pull the spark plugs and see if they are fouled.
Is there anything els I can check? any suggestions would be greatly appreciated.
P.S. I was told that my original problem with engine running with vacuum hose removed means that the engine is starving for air.
Bill
sorry for the long post

 

The plug that you pulled, was it soaked with gas? That may indicate that you have something in the fuel bowl of the carb that is keeping the needle from sealing on the seat thus causing you to have a continuous flooding condition. Pulling the vacuum hose off may have allowed enough air to somewhat balance out the fuel to air ratio so it would run. Might want to take the top off the carb and see if you need to clean out some debris. Let us know how it's going.

 

hdgapeach, yes the plugs were wet. Today I picked up some new plugs and wires, installed them. Had to hold the pedal to the floor but it did start.
When I had the carb off, I did tilt it to check the bottom of the carb.
You suggested pulling to top off the carb to check for debri in the float bowl. Can I safely remove the top with the carb still mounted on the intake? Are there any springs or ball checks in the top that will fall out?
I plan on installing an o2 sensor to hopfully take care of it running rich. I hope it does lean it out some because it sure is going through gas at a rediculous rate and it's not even on the road yet.
Thanks for your help. I will keep you posted on cures and progress. Unfortunately I have to work outside and it is cold out there here in pa.
Bill

 

You may have a stuck open power valve, (on the fuel enrichment circuit) Is this a one barrel Carter? Some carbs have 'power valves' others have a 'fuel enrichment circuit' that accomplish the same thing but use stepped rods in the main jets. Vacuum holds the rods down to keep the jets running lean. Without vacuum on those rods, they ride up out of the jets and allow full flow of gas, making it run rich.

Carter uses the rods. Motorcraft/Holley use that valves.

If you have an electric fuel pump you can turn on the ignition and see fuel pouring out of the top of the carb vent into the venturis which will indicate a stuck or malfunctioning float and needle.

 

pops_91710, yes it is a carter 1 barrel feedback carb. I know that this carb does run rich without the cpu. Knowing this, I know that I need to install an o2 sensor to lean out the carb air/fuel. The o2 tells the cpu how to adjust the air/fuel.
Thanks for your input.
Bill