carb adjustment question

[bassackwards]

I have a Holley vac secondary carb on a 350 that is impossible to start when cold from inside the truck. It just will not start. When I move the throttle I am not getting a shot of gas.

If I manually move the accelerator pump lever I'll get a shot of gas and then it will start. I don't think the cam on the throttle is adjusted properly because it never engages the accelerator pump.

How do I adjust it?

 

[nvrenuf]

I don’t remember the amount but iirc it’s adjusted by using a feeler gauge for set the gap between the arm and throttle linkage at WOT.

 

[diesel4me]

My experience with Holley carbs is limited,because I never had much luck with them except for a few spread bore Q-jet replacements and their Economaster series,but I do recall them having a multitude of different accelerator pump cams,secondary diaphragm springs,etc,that had to be experimented with to find which one worked best for your application and climate..

If the carb has a choke it should start without any pedal pumping really,but it will bog out and want to die if you stab the throttle if the accelerator pump isn't working..

 

[wasted wages]

Pretty simple to adjust...watch the entire video .... lots of good tips.

skip to the 5 minute mark to watch the accelerator pump setup and adjustment.
Holley makes several pump cams for tuning, so make sure you have the original cam if you want the original setup from the factory.

Edit: Make sure you don't have any vacuum leaks...very important !
Check all your hoses, and carb mounting gasket, PVC valve and hose, and the vacuum booster hose. If you have had a lot of backfires thru the carb, there's a good chance that the power valve inside the carb may be blown. Depending on what year the carb was manufactured, Holley added a little check valve to prevent the power valve diaphragm from being blown out from backfires thru the carb.

I mentioned this because if you have been experiencing lean conditions under acceleration carb backfires are quite common...