1987 F350 460CI Auto Trans. Holley 4180 carb. Got it back on the truck and everything works great except, Immediate hesitation when just barely pushing accelerator pedal. Its very strong when not in gear and does not hesitate only happens when in gear. Its just that first start hesitation. Other then that this thing hauls ***!!!! I've adjusted the Accelerator Pump. In the rebuild kit the squirt-er was taller then the one I took out. Ended up putting the shorter one in and no difference. BTW its a #28 Think I'll try adjusting the 2 air mix screws on the base plate tomorrow and see if that helps.

Any Ideas on what might be going on?

 

Not familiar with your carb so this is just general info. Need to have float level correct, need choke to be working properly, need to check for vacuum leaks, need to check ignition timing.

 

I adjusted my fuel/air mixture on the carb. today used a vacuum gauge and still no change. I also messed with the Accelerator Pump adjustment. Still no change. Checked my float bowls and they are good. Everything on this carb is perfect except the initial start from a dead stop. And it only last for 2 seconds tops. Once I get past the short hesitation it rips ***. It either wants more air or more fuel. Wondering If I should try changing the accelerator pump discharge nozzle or squirter. Its got to have something to do with the Accelerator Pump or that float bowl side.

 

I would think it probably is an accel pump problem.Run the engine at idle for about 30secs and shut off. Look into the carb throat and work the throttle linkage by hand, there should be no delay when the accel pump shoots gas into the throat.
I would also check the condition of all vacuum pipes, including the rubber one that connects to the vacuum modulator at the trans. jsut in case there is a small vacuum leak.

 

agree, pump problem. sounds like you have a flat spot in the pump. in other words theres a spot where the pump isnt squirting any gas.

 

Don't think I'm getting a vacume leak. I hooked up a gauge and its steady at 20.... There is something happening between the pump and the squirter. If I throw my other carb on it runs fine. And like I said everything else with the rebuilt carb is fine... This carb I rebuilt is from a junk yard. I need this truck to run so I decided to have 2 on hand in case anything happened. For 50.00 how can you go wrong and the 89.00 for the rebuild kit. I decided to rebuild it myself since the Hot Rod Guy I ask to rebuild it wanted 350.00. I had heard from this forum there is not much to this carb so decided to take the challenge. They were right not many parts. Only thing that startled me was the use of ball bearing replacing needle valve under the squirter and a couple of other uses for ball bearings. I'm becoming an expert at removing carbs from this truck, takes me less then 10 minutes.

 

Meant to mention I may put the needle valve back in and take the ball bearing out. Well see what happens.

 

That may be your problem. If memory serves, all the 4180's used the needle valve check, not a ball.

 

That's what I thought, but I did what the instructions said to do. And I do remember replacing the needle valve with a ball bearing which I thought odd at the time. Think I will pull the carb tomorrow and replace the ball.

 

The needle or ball in the squirt passage SEALS the passage against pumping fuel BACK into the bowl when the accelerator pump operates. If this check valve action leaks the tiniest bit, much of the fuel intended to go INTO the cylinders, goes BACK into the fuel bowl.

If not too much work to gat at it, and if it's like the OLD Holleys of years ago, there is a nozzle-like part, maybe that's what you are calling the "squirter"? Held in place with a single Phillips screw. Take it off, put a correct-sized short piece of rubber tubing on an air blowgun, seal the tubing tight against the passage where the squirter was removed, apply LOW-PRESSURE air, regulate it down to no more than 5 or 10 psi AT MOST. Carefully apply pressure, if the check valve leaks, you will hear (and maybe SEE, if you remove the float-level screw) that the needle or ball is leaking. It may be that the SEAT which the part seals against is cracked. If that's the case, ya gotta live with the hesitation, or replace the carb main body. Just my 2 cents. impish

 

Actually, the needle under the pump squirter prevents fuel from being pulled through the pump squirter by venturi vacuum while the engine is running. Under (actually on top of) the accelerator pump diaphragm there'll be either a check ball or a little rubber check valve that prevents fuel from going back into the fuel bowl when the throttle is applied.

 

Checked everything again including the Accelerator Pump the check ball and the squirter and ball below the squirter. Can't find anything wrong. I put the other carb back on and giving this up for now. The other carb works fine the only problem with it is the gas filter housing was stripped so I epoxy it to the float bowl housing a installed an inline fuel filter.

Will be dealing with the RABS brake module tomorrow. First pulling the spring out and reinstalling the nut. This will tell me if its bad or the master cylinder is bad. Sinking brake pedal while at stop light is the problem.