first of all my truck is a 1970 2406cyl. 1bbl. 3spd. all manual

i have a little round canister looking thing with a spring attached to the bottom of it. it looks like this can be adjusted. All of the vaccum hoses come together to this little canister and plug in it. what is is? how could i adjust it? and would something wrong with it cause the hesitation??

 

It sounds like your describing the vac. canister. It looks like a high quality, high tech coffee can right? I have never seen one with a spring attached to the bottom. The only thing I can think of is it allows you to adjust your vac. Please correct me if I'm wrong guys. It sound have nothing to do with your hesitation unless you have a vac. problem. Jack

 

mine is only about 2 inches round and 1 inch tall. it dont look like a coffee can.

 

Where on the engine is it located?

 

its located right in front of the distributer and mounted a little bit above the valve cover

 

Ideal: I am thinking you are describing a vacuum hold valve. Here's what it does: Your vacuum accessories (including the distributor advance, EGR, etc) all need vacuum to work. As long as the engine produces high vacuum, everything is OK.
However, there are times when vacuum drops, sometimes almost to zero, and that's when the vacuum devices quit working. When you stomp on the gas, for example, vacuum drops, regardless of engine speed.
So, there is a one-way valve in the vacuum line, that holds the vacuum steady on one side (the accessories side) until the vacuum builds up again in the supply side, that is, from the carb.

If that valve quits working, then you lose vacuum to the accessories everytime you accelerate. The problem will be most noticeable when you start moving the truck from a stop, such as from a stop sign. Vacuum drops the most then.

Be advised that other things than cause the loss of vacuum. If there is a bad diaphragm in the EGR or distributor or anything else an automatic transmission modulator, you will get the same effect.

Other things causing loss of vacuum are cracked hoses and connectors (don't overlook metal vacuum connectors which were cracked by bending back into place.)

Finally, the most common cause of vacuum-loss caused hesitation is a worn out accelerator pump in the carburator. Worn out carbs comne second.

Hope this helps!

 

i think that helps some. ive got another old junk truck with a 240 in it. i'll try using that little valve off of it and see if it helps the hesitation in it. i have a new accelerator pump ( first thing i tried), so i know thats not it