First post, weird problem

[eazzrider]

Hello and thanks in advance for all the good info on the site. Here's the deal, Son recently purchased a 72 C10 with the 250 and three speed on the tree. 56,000 miles super clean and rust free. Truck has been setting for a long time. Runs like a champ but won't idle smooth. I have the idle turned up to keep it smoothed out. You can get going down the road, put the tranny in neutral, hit the brakes and the engine will die. It does not have a vacuum assist on the brakes. When the front end dips the motor dies. I can go in reverse and do the same thing and the engine speeds up. With it idling fast in the driveway I can bounce the front end and make the rpm's swing all over the place. What gremlin is in this thing? Thanks,

[DT1]

The first thing I would do is check the float level. If you have a phenolic float, it might be time to replace it as they will "Gas log" over time had cause the fuel level to rise.

[C10 - C90 Bill]

For it sitting for that long, you may want to just rebuild the whole carb, along with the Float. I believe the kits are pretty reasonable. You may also want to empty the tank and change the filter(s) as well.

Bill

[eazzrider]

Filters are new, inline aftermarket and the one in the carb. Got a kit coming, will order a new float too. Just seems like a strange problem.

[DT1]

Originally Posted by eazzrider

Filters are new, inline aftermarket and the one in the carb. Got a kit coming, will order a new float too. Just seems like a strange problem.

Not strange at all. If the float sinks the fuel level will rise and cause the engine to flood. Running it at high idle can be enough for the engine to consume the excess fuel before the fuel pump can replenish it.

[68gmsee]

When the engine dies, does it start right back up?

There's only very few things that can cause the problem as you describe it. First is carb float problem. You may also have a loose carb gasket or in other instances an electrical connection that's wiggling around when you bounce the truck. Could be in the coil area or in the distributor. Try moving, wiggling or tapping them to see if you get a reaction.

Also, just for kicks, get some starter fluid and spray lightly on the base of the carb and around the intake for any slight increase in rpms. I've had those mono base and middle gaskets get loose and cause problems. The middle gasket can only be accessed by removing the carb. Two big screws under the base become loose.

As a last resort, remove the distributor and check it thoroughly for any problems.

[kcsa75]

I don't know squat about carburators, but welcome to the board. There's a lot of knowledge here. I'm sure somebody will help you solve your problem!

[70cst]

Hey eazzrider ... from Ohio...Here is a bump for you

[cdowns]

i'd make sure the tank is not filled with crap and sludge/ there is a screen on the fuel pickup inside the tank that gets clogged up causing fuel supply problems

[blkcorvair]

For an air leak those are good suggestions. Spray some Carb cleaner or Starter fluid around the base of the carb and see if there is a change in RPM's. If si you have an air leak (Probably a bad gasket) A really worn throttle shaft will do that too, but with only 56k it probably is fine. Definatally get tht carb rebuilt though.

I diodnt hav the stalling problem but even after rebuilding my carb I still have the rough idle. Seems a lot of these 250's do. (Turns out mine was packed with sludge.) But I had alot of play in the throttle shaft on the carb, A worm out distributor, and a pretty well worn cam and lifters.

Welcome and post some pics of your new ride!

['68 C-20]

Yup, dried out, dry rotted, carb base gasket could well be the culprit. The resulting Vacuum leak messes with the ability to draw fuel at idle speeds. Good news is that the gasket comes with the kit.

Be careful spraying the starting fluid around the motor, is is obviously very flammable and old arcing plug wires could set off an unwanted situation that will leave you lacking eyebrows, or worse. Just use a small amount, directly at the base of the carb. Carb Cleaner will work and is a little bit safer, but IMO does not work quite as well. ('Cause it is safer).

If I had a kit on order and were going to replace the carb gaskets anyway, I would just leave the can on the shelf unless the carb kit does not solve the issue.