Just got a used holley 750 4160 and rebuilt it for my buddy, there was no needle under the screw in the pump nozzle on top of the carb just the squirter nozzles base piece and the little ball inside there. Also when I press the pump lever manually when engine is idling, there is no resistance whatsoever and zero pump shot out the top. I'm not sure how to go about fixing this issue, anyone with some good Holley knowledge would be helpful. I'm pretty sure I assembled the pump diaphraghm and what not correctly, but I could be wrong. I've looked around on google and couldn't find any good tutorials with pictures detailing how the acc pump circuit goes together. Any help would be appreciated...
Is this an older 4160 with the red umbrella type check valve under the pump diaphragm instead of the staked in check ball? If so, is it installed correctly?
If you remove the pump cover and the diaphragm, there should be a spring under the diaphragm. Without it, the diaphragm won't suck fuel from the bowl and re-fill. Also, there will be no resistance when pump it by hand for two reasons, The pump spring is missing, and there is no fuel under the diaphragm.
Make sure you used the correct gasket under the squirter. Use the wrong one and fuel can't get by it. The picture of the components are very small that come with the kit and it's hard to tell which one is correct, so use the one that is just a bit larger than the screw but small enough to seal the squirter base. I'll assume you got the diaphragm in correct as the small metal contact for the pump arm is pointing towards the arm.
Just got a used holley 750 4160 and rebuilt it for my buddy, there was no needle under the screw in the pump nozzle on top of the carb just the squirter nozzles base piece and the little ball inside there. Also when I press the pump lever manually when engine is idling, there is no resistance whatsoever and zero pump shot out the top. I'm not sure how to go about fixing this issue, anyone with some good Holley knowledge would be helpful. I'm pretty sure I assembled the pump diaphraghm and what not correctly, but I could be wrong. I've looked around on google and couldn't find any good tutorials with pictures detailing how the acc pump circuit goes together. Any help would be appreciated...
If there's a check ball alone below the nozzle, that's not enough to seat it- there is supposed to be a small weight on top of the ball. The other type of check found below the nozzle is a longer pin-type check.
The other check located above the diaphragm should also be checked, as has been said. There are two types, if you have the the ball-type, they can corrode around the seat and are a bit tricky to rework the seat. Instead of going into the whole procedure, I'll wait to see what you have.
And replace the spring above the diaphragm if it's missing- which sounds like what has happened.
If you need a spring, PM me and I'll send you one, gratis.
Wow thanks for all the quick replies... I found the accelerator pump spring in my box of parts.... whoops. I'll put that in and move on from there. There's the diaphraghm, the spring and the rubber umbrella right? Anything else in the pump itself? I'm not quite sure how to tell what type of squirter I am working with, I can remove the screw and take pictures if that helps, let me know what I need to find out about it to get this sorted out.
Wow thanks for all the quick replies... I found the accelerator pump spring in my box of parts.... whoops. I'll put that in and move on from there. There's the diaphraghm, the spring and the rubber umbrella right? Anything else in the pump itself? I'm not quite sure how to tell what type of squirter I am working with, I can remove the screw and take pictures if that helps, let me know what I need to find out about it to get this sorted out.
The spring goes against the bowl itself, then the diaphragm then the cover and the 4 screws.
If you have just the ball, look in the kit left over parts for a small barrel-shaped piece the same diameter as the check ball. That would be the check ball weight.
If your carb has the rubber umbrella style check under the accelerator pump housing, I think it should use the long, pointed check under the nozzle- hopefully someone else will chime in here if they know if this is or is not correct.
There was no check ball weight or check ball in the nozzle when I got the carb. The carb wasn't together when I received it so it's proving difficult to sort out. I don't think I have the long, pointed check to go under the nozzle like you talk about. I'm not quite sure what one would look like though, or how to go about getting one.... thanks again.
The ball looks like, well, a ball. Shiny, steel. The weight on top is 5/32" diameter (as is the ball), and about 1/4" long, IIRC (I couldn't lay my hands on the weight just now).
The ball looks like, well, a ball. Shiny, steel. The weight on top is 5/32" diameter (as is the ball), and about 1/4" long, IIRC (I couldn't lay my hands on the weight just now).
The check wieght for use with a ball will look just like the pointed weight shown in the pic, ...with the pointed part cut off
Be sure on the accelerator pump shooter that you are using two gaskets...one under the head of the screw (gets crushed into a tapered shape) and one flat under the shooter against the base casting. Look like bowl screw gaskets but are real thin.
What the check valve or ball does under the squirter is let fuel travel in only one direction (out the squirt nozzles). When you let off the gas the valve or ball seals the squirter's while the accelerator pump refills from the bowl. Without it, the squirter passage from the pump will fill with air and create a bog the next time you step on the accelerator.
Attn. has to be made when installing the metering plate and bowl gaskets as there is a small hole in both of them. the gaskets have to be aligned correctly or the pump reservoir won't be able to refill. With the carb sitting on the bench, the hole will be found on the bottom right of the bowl and metering plate. Being you have a DP this will pertain to both ends of the carb,
primary and secondary. You might want to check the secondary's also as you can have the same results when you stomp into them.
I just rebuilt my first Carburetor and I find two issues now.
1. The Fuel Transfer Tube is leaking heavily on the secondary side
--- I think it is to do with the o-ring. I am going to try and replace that and see if that solves the problem.
2. After putting everything back together, I am left with one part that I dont know where it goes. It is verysimilar to the needle that was posted on this forum. I saw it fall out of the carburetor when I trned it upside down.
Please advise! I do appreciate the insight from more experienced people.
PS- I am using a 4160 600CFM carburetor - List number 1850-3.
Seeing is how this is an old thread. visualideas send me a private message and I would be able to help you as I know that carb like the back of my hand and currently run the exact same carb on my milder small block chevy.
The thing your talking out that fell out as you turned it over would be the shooter check weight and where it goes is underneath the shooter. Take the shooter off and be careful as there are two gaskets with one being under the shooter housing screw and the other will be at the bottom of the shooter.
And as far as your fuel transfer tube on the oldest ones they had a radius to which a regular o ring would fit up against and seal it against the fuel bowl. If this is the one you got holley has changed the tube to just being a regular tube with no radius and in the newer rebuild kits the new style of seal gets pressed on the end and is a way better improvement over the old design.
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