720 coldstart issue

[Mike8199]

so everytime my truck cools down and i go to start it, for one i have to give it some gas while holding the key (not that big of a deal), but it also will revv up to like 2500 rpm and sit there until it is warm enough to where when i tap the throttle it comes back down to normal 900ish. If the truck isnt warm enough yet and i tap the throttle it just goes up and comes back down to like 2000. any ideas on the high revving and sitting there on cold starts?? 

 

Ps. i recently changed my ported vacuum switch because the other one broke. i though for sure that would be the fix, but no change.

[]2eDeYe]

Sounds like the choke is out of adjustment or not working correctly. 

[captain720]

Do you have an electric choke Weber? Check the voltage on the little power wire with a multi meter.

 

 

 

Also when it gets warm an open choke looks like this.

 

 

 

There is also an idle screw that may warrant checking, although it should not change too much when the rig warms up.

[datzenmike]

so everytime my truck cools down and i go to start it, for one i have to give it some gas while holding the key (not that big of a deal), but it also will revv up to like 2500 rpm and sit there until it is warm enough to where when i tap the throttle it comes back down to normal 900ish. If the truck isnt warm enough yet and i tap the throttle it just goes up and comes back down to like 2000. any ideas on the high revving and sitting there on cold starts?? 

 

Ps. i recently changed my ported vacuum switch because the other one broke. i though for sure that would be the fix, but no change.

 

Pretty sure the later 720 choke is not adjustable and sealed at the factory. Assuming you and any PO has not messed with it then I would suggest spraying carb cleaner of WD-40 on the back of the carb where the throttle cable is. Hold the throttle half open and close and open the choke plate by hand several times to loosen and lube all the moving parts. Be sure the plastic fast idle cam is free to Move into place when the choke is closed and drops out of the way when you open it.