I rebuilt a '69 Roadrunner carb, and the accelerator pump doesn't squire till the secondaries start opening. The spring on the pump compresses without the piston moving at first until it can overcome the spring under the pump, and the resistance of the fuel. There was no check valve in the carb. I took one from another AVS that had been messed with. The pump works the way the FSM says to test it, but there is no fuel squirting while only operating the primary throttle. The secondaries are adjusted per FSM, two complete turns after the air door just starts to close. The thing just doesn't have crisp throttle response, and that's just in neutral. Timing is 38deg. total with vacuum disconnected. It idles with the throttle turned one and a half to two turns from fully closed, and there's vacuum on the ported vacuum port. I'm wondering what to do next.

Compare the spring on the new pump from the kit and your original pump. Does the new one appear thinner or weaker?
Doug

No, seems the same. Saw a Youtube where someone showed the two different pumps. Both of mine are the smaller spring. The bigger one was noticeably thicker, said to be used on the larger carbs. I don't think the kits differentiate that.

What size and weight check valve did you use?
It should start to squirt when the pump skirt is at the top of the fuel inlet slot, I check them that way without the tops first to make sure the pumps work

What size and weight? How do I quantify that? Are there numbers on them? It was a triangular shaped rod about 7/16" long.

there are several different version of the check valve that will go into those holes, both triangle and square versions. Can you take a picture of yours and post it on here?
You might want to check the seat in the carb where the check valve seats to make sure it isn't corroded a bunch, if it is corroded that will allow the gas to be suck out of the well when driving it making it not pump also.
How about the check valve at the bottom of the accelerator well, is it sealing when being pumped or allowing the gas to be push back into the carb body?

i use a 4618s on the 440 in my '69 r/t. i don't use the leather stock pumps. i use the "orange/tan" colored edelbrock pump set on the top hole. i also down sized from the stock squirter (.033") to an AFB .028" squirter. carb uses the factory check valve in the pump circuit and float bowl. works great.

As mentioned don't use the leather pumps the alcohol in today's gas messes them up fairly quickly. I use the rubber Edelbrock ones, and if I remember right there are a couple different diameters, so you have to get the right one. I buy the cups on ebay in bulk. Next is the check valve under the accelerator squirter, I think stock it is a brass needle. Many times the brass ones corrode and hang in the body of the carb stopping the flow of fuel. I have been replacing the brass needle with just two steel check balls. Makes the squirter react faster. So when rebuilding the cab simply fill the well with some fuel before you put the top on and work the plunger to see how the squirter works. Make sure the spring above the cup is strong enough, if you stretch it a little it also will make the pump, work better. Next make sure the pump height adjustments are correct, if the pump plunger is too high it will be above the slot that is in the carb body and will not compress fuel until it gets past the slot.

I see the spring I'm talking about is called a delay spring. Well, that's what it's doing. The bottom of the squirter port is clean and shiny. The needle moves freely. I'll try and stretch the delay spring out a bit. I've read some people make the needle shorter/lighter, and some people say to never do that. The 4618 eBay carb I rebuilt years ago worked fine, and still does. No delay in the pump. I can't remember what kind of check valve it had, though.

this sounds like an extreme case. it could be that you have a '68 or earlier pump in the larger '69 and latter pump well. big difference between the two.

The delay spring should not be a heavy spring. Originals are thin dia coil wide spacing. The spring on the pump is heavier. There were different diameter pumps, and the cylinder can be worn. But since you say your collapsing the pump rod, that eliminates undersized pump and even missing check valve, all which would reduce pressure against the pump going down. So it seems to me the pump spring and delay spring are swapped or wrong.

The check valve under the carter pump housing are brass with point. They can get stuck, but if it does shoot at some point something is off. I have seen folks add ball bearing on top of it for some reason. As long as not rigged somehow it seems to me the springs are the issue.

One last thing, no free play in the lever on throttle shaft going to the pump rod causing it to delay movement?

I have had AFB and AVS carbs with the same trouble. As mentioned you might try an edelbrock accelerator pump or call one of the carb specialists like Harms. In my experience the accelerator pumps supplied in the Hygrade kits usually don't work correctly. The accelerator pump should spit fuel as soon as the on the throttle linkage moves.

I took the needle and return spring out, and it acts the same. It's like the leather seal is creating more friction than the delay spring rate. I stretched the delay spring out a bit, put the needle and return spring back, and I think it's even worse. Looking at the pic blown up, the new seal's starting to look worse than the old one. Guess I've been messing with it too much. Guess I'll try one of those viton, or whatever rubber type seal.


Needle, return spring, nozzle, old, and new pump



Down the discharge nozzle channel.

Ok, Standard Motor Products is Hygrade, right? Lol, that's what I've been using. They used to be top of the line when I was taking auto shop in school.

try putting some engine oil on the new pump and use a thin screwdriver or small nail to push the plunger skirt out some and then try it in the pump well with the carb top off to see if it will squirt that way

I did soak it in oil first, then flared it out a bit. It's sealing fine as no fuel leaks past it. It just builds up more pressure than the delay spring can deal with. The way I would imagine it's supposed to work is the linkage pushes the shaft down faster than the pump can push all that fuel out, so the spring compresses, and keeps pushing fuel out for a second or two while the throttle is already opened all the way. It should still pump fuel out anywhere in between idle or full throttle. It doesn't. The pump stops until the delay spring is completely compressed, then it starts squirting.

What is your carb number? The other thought is I believe the early AVS used the 11/16" pump dia, and they moved to larger diameter later years. If the pump diameter is too large you would have more friction. You can measure the washer diameter above cup. Compare to body diameter in well.

Sounds like you have a restriction in the passage to the squirter or a weak spring behind the pump. Take the squirter off and the check needle out and just stroke the pump to see if it flows freely. You cannot compress a liquid so the spring behind the pump is there, so you don't bend or damage the linkage when you open the carb quickly. It is supposed to compress and then allow a steady stream of fuel as the spring pushes the plunger down. Again try removing the brass needle and replace it with two small check balls. I say that from experience. I have a lot of carb parts and pieces laying around so it is easy for me to experiment, I am just assuming you would have some laying around as well. And of course they must be small enough to move freely under the squirter.

as cruddy as that old pump plunger looks there could be a carbon build-up in the passage from the pump well to the discharge port. i usually take a small wire tie and run thru those passages to dislodge stuff. also, you need to look at the pump well check valve at the bottom of the pump well. that check valve unscrews like a jet but has a check ball in it. it's supposed let fuel in the well on the upstroke and block fuel going back into the float reservoir on the down stroke. if the ball is stuck open then fuel from the pump well will discharge back into the float well. if the check valve is plugged along with an obstruction in the discharge line nothing will work. i don't like those pullover squirters but they can be used. there should be a number on top of the squirter telling you what size the discharge orifices are; probably 33. find a 1/32" drill bit and clean those orifices out.

The inlet check valve is fine. If I plug the outlet, and push down on the plunger, both slowly, and forcefully, and no fuel backs out of the inlet check valve either time. With the outlet check needle and squirter removed, I can push down on the rod, the spring compresses without the plunger moving, then when the rod is completely collapsed, the plunger moves down, pumping gas out the discharger freely, lots of flow. Did this without the return spring installed, too, so all I can think is the leather seal has too much friction. I'll try the Edelbrock 1470 pump tonight and see what happens.