Just put a kit in my Quadrajet and everything works great, except my accelerator pump. I'm getting no fuel discharge when I actuate the pump mechanism. I've taken the top off and checked all the passages for obstructions. With the carb top removed I can depress the accelerator pump and get fuel to discharge through the passages, but with everything assembled, nothing. The kit came with a new diaphram for the pump, which I installed and I squirted all passages with carb cleaner and compressed air. I checked for the check ball in the pump discharge port and it's there. Also checked to make sure a passage wasn't obstructed by the gasket and can't see any obvious obstructions. Any ideas as to what's wrong? I'm stumped.

Do you have both the pump and the spring installed?

http://www.stratagaz.com/Quadrajet/22%20-%20Accelerator%20pump%20install.jpg


Kind of sticks up when you install it:

http://www.stratagaz.com/Quadrajet/24%20-%20Air%20horn%20install.jpg

Do you have both the pump and the spring installed?

http://www.stratagaz.com/Quadrajet/22%20-%20Accelerator%20pump%20install.jpg


Kind of sticks up when you install it:

http://www.stratagaz.com/Quadrajet/24%20-%20Air%20horn%20install.jpg

Yep, it's in there. I went back out and was adjusting the idle and the pump seemed to be working when the car was idling, but it wasn't working this morning before I started the motor. It did the same thing yesterday, no fuel discharge when I tried to start the car (it did have fuel in the bowl, though). I should be able to see fuel dischage without the motor running by moving the throttle shaft, right?

If the float level is too low, fuel will feed into the pump cavity and hense, no discharge.

If the float level is too low, fuel will feed into the pump cavity and hense, no discharge.

Agreed....No or too low fuel in carb equals no pump shot. How long did the car sit before you tried to start it yesterday? Did you epoxy the plugs when you rebuilt it?

http://www.stratagaz.com/Quadrajet/02%20-%20Fuel%20well%20plugs.jpg


I should be able to see fuel dischage without the motor running by moving the throttle shaft, right?

Yes if there is enough fuel in the carb.

I did epoxy the well plugs with JB Weld during the rebuild. I also set the float (new) to the recommended height, which I believe was 11/32". Per the instructions, I took the measurement from the top of the float (with inlet valve fully seated) to the top of the fuel bowl casting. I did see fuel in the bowl, when I had the carb apart checking the accellerator pump. What should the float height be set at? Or did I set the float height wrong?

Sounds like you set the float right. I Wonder if you have the acc. arm in the right hole. Just a thought. You should get several pumps in the morning engine off.

Sounds like you set the float right. I Wonder if you have the acc. arm in the right hole. Just a thought. You should get several pumps in the morning engine off.

This isn't the first Q-Jet I've ever rebuilt, but it is the first one that's given me this problem. I've got the linkage installed in the cam position furthest inward, to give me the quickest fuel shot. Not sure if this is worth mentioning, but the carb top is wet around the accelerator pump shaft, like fuel is being pressurized past the seal when I acuate the linkage.

Thats the position for it. Could it be running hot from something causing it to boil. Mix, shroud missing, coolant mix...... Its amazing how hot a lean mix can be.

Thats the position for it. Could it be running hot from something causing it to boil. Mix, shroud missing, coolant mix...... Its amazing how hot a lean mix can be.

Nope, running temp if fine. A passage must be clogged or a gasket blocking one of the passages. I really hate to totally disassemble this thing again, but looks like that's the route to go. Good thing this isn't a daily driver!

Tom, my Qjet was running good after my regular mechanic rebuilt it but always a flat spot on startup or acceleration. He couldnt tune it out at all. I finally took it to a buddy that rebuilds Vette's and he looked down the throat while at idle and pushed the pump down, 'nothing came out'... he said thats odd. He pulled the top off and pulled the pump out. The leather (rubber?) that came in the kit was too narrow and gave no tight fit to the sleeve it sits in. He opened a plastic box of carb parts and had 5 other sleeves for different carbs. He pulled out a wider one, stretched off the old one, put on the new one and reinstalled it. WORKED like a charm then. The dang kit had the wrong leather (rubber) boot on the plastic pump.
Try to widen your leather with a screwdriver or nail first. If that helps, (it will return to its original size), remove it and replace with wider leather (rubber). See if that takes away your goblin like it did for me. :thumbsup:

Do you have the pump discharge check ball installed?

Do you have the pump discharge check ball installed?

If your talking about the check ball that fits underneath the screw/metering device that resides in florr of the float/bowl area, yes. If there is supposed to be a check ball underneath the accelertor pump, no I don't.

Jim, my new accelerator pump cup (made out of rubber) seems to fit tight. However, NAPA sells that piece for under $3.00 bucks, might be worth a shot to change.

Thanks guys for the input.

Like "Click" (Jim) said, I've also seen the Cup be distorted in some of the 'quicky' kits - easy part to replace.
Did you reuse the original pump plunger and duration spring assembly? If so, is the spring retainer in the correct slot/groove?
Also, is the plunger tip contacting the lever-arm at the rest position? There should be no gap between the lever and the plunger tip or pump action will be delayed at throttle opening. Make sure the plunger return spring is in place and properly seated to push the plunger all the way to the top of it's stroke and in contact with the lever.
Oh, there is only one (1) check-ball in the discharge passage, right under that retainer screw ;)

Like "Click" (Jim) said, I've also seen the Cup be distorted in some of the 'quicky' kits - easy part to replace.
Did you reuse the original pump plunger and duration spring assembly? If so, is the spring retainer in the correct slot/groove?
Also, is the plunger tip contacting the lever-arm at the rest position? There should be no gap between the lever and the plunger tip or pump action will be delayed at throttle opening. Make sure the plunger return spring is in place and properly seated to push the plunger all the way to the top of it's stroke and in contact with the lever.
Oh, there is only one (1) check-ball in the discharge passage, right under that retainer screw ;)

The kit I got didn't have anything for the pump, except the "cup", so I had to reuse my accelerator pump parts. I called around some of the local parts houses, but nobody had a new accelerator pump, just the cup gasket. I had to slightly depress the pump cam to insert the roll pin through the cam when I reassembled the carb, so the pump is definelty loaded. I'm probably going to go get the cup gasket from NAPA, take everything apart (again), blow it out with compressed air and recheck all the gaskets to make sure they aren't plugging up a passage.

You might take some petroleum jelly and lube the bore for the cup to slide into place without rolling. You might also have to place the rod in the upper pump arm outer hole for more volume to eliminate the bog.

If you have pumping action with your finger and not the linkage, the pump rod from the throttle plate linkage may be in the wrong hole.

Move the throttle minutely, fuel should dispense.

You might take some petroleum jelly and lube the bore for the cup to slide into place without rolling. You might also have to place the rod in the upper pump arm outer hole for more volume to eliminate the bog.

If you have pumping action with your finger and not the linkage, the pump rod from the throttle plate linkage may be in the wrong hole.

Move the throttle minutely, fuel should dispense.

Outer hole? Inner hole? The hole closest to the carb body will give the pump more movement.

If it makes you feel any better I had to rebuild mine several times before I got it right. Each time I took longer and was more watchfull. Did you get a kit with your carb # or year make and model?

If it makes you feel any better I had to rebuild mine several times before I got it right. Each time I took longer and was more watchfull. Did you get a kit with your carb # or year make and model?

Carb kit was based on carb number. I suspect there's an internal blockage somewhere, since a small amount of fuel is being forced out the top of the carb where the accelerator pump shaft passes through.

... I suspect there's an internal blockage somewhere, since a small amount of fuel is being forced out the top of the carb where the accelerator pump shaft passes through.

Yup, fuel will not compress very well ...
I've seen incorrect size check ball, gasket mis-match and stuck plunger pistons do the same thing your seeing.

Sling the Quadrajunk as far as you can throw it or destroy it with a woodsplitting maul...and get a Holley Spread-Bore... chuckle. Just a little levity. Never did like a Quadrajunk.

Stupid question, but did you use carb cleaner AND compressed air (with strong velocity) to blow out all the tiny passages? Old carbs that have been sitting around are famous for accumulating plenty of gunk on the innards. Many times, I've had to use a small screwdriver to scrape the stuff out. When I have a carb body all apart, I am always careful to blow the crap out of all the passages. I will typically soak parts in powerful cleaner overnight (NASTY STUFF), then drain, wash, and then use spray cleaner to attack the small passages. The spray nozzle stream acts like a visible guide to see if the passages are clean. In other words, if I spray downwards into the pump shot discharge passage, then I look into the pump fill area and I should see fluid coming out. All passages can be checked this way................

Of course, as already stated, you might be missing a check ball, or perhaps have wrong gasket, or incorrect pump seal. These old Q-jets had many different part numbers and you need to get the absolute correct kit. Even with the correct kit, there are often multiple gaskets to choose from, so you gotta make sure you use the right gasket.

I used to "tweak" Q-jets for the local street rodders (30 years ago, lol) and a Q-jet would work GREAT if set up properly. Plus the engine looked stock with a Q-jet and it was easier to get a $50 race with a stock-looking engine. If you had a shiny Holley 850 DP sitting there, then you'd usually have to give up a car or two on the start. ;)

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one very inportant item that is very often over looked- there is a tin gasket put on the intake(a stock one has exhaust holes going up to the base of the carb) and then the regular carb gasket. too much heat can cause this problem and the car will run like s#"*--also the carb will vaporize gas after the car is shut off and make it hard starting on a restart--i have been a tech for over 35 yrs and Q-jets work great if done properly-a very simple carb

I took the carb apart, sprayed out the passages, reset the float level (it was a little low and checked the accellerator cup gasket. Whatever I did seems to have fixed the problem. I have a slight secondary bog, which I've almost fixed by adjusting the secondary opening rate. I know that the vacuum brake (canister) that dampens the secondaries from opening too fast is bad, so I need to replace that before I mess with the opening rate any more. Otherwise it runs pretty good. Thanks for all the advice.:thumbsup:

.............I know that the vacuum brake (canister) that dampens the secondaries from opening too fast is bad,.........

That's your "air valve dashpot". It's easy to test and they often go bad. Compress it and put your finger over the nipple (or just suck on it like a straw and it should close). It should stay closed. If it opens, then the diaphragm inside is shot and you need a new dashpot. If it's bad it will allow the air valve to open too fast and cause a bog.

You should be seeing a good, healthy shot of fuel from the accelerator pump, as you work the throttle, looking down the primaries.

Also, if you've messed with the secondary air valve spring, then I would consult the manual and set it back to factory specs.

Glad to hear you're making progress.

:)

That's your "air valve dashpot". It's easy to test and they often go bad. Compress it and put your finger over the nipple (or just suck on it like a straw and it should close). It should stay closed. If it opens, then the diaphragm inside is shot and you need a new dashpot. If it's bad it will allow the air valve to open too fast and cause a bog.

You should be seeing a good, healthy shot of fuel from the accelerator pump, as you work the throttle, looking down the primaries.

Also, if you've messed with the secondary air valve spring, then I would consult the manual and set it back to factory specs.

Glad to hear you're making progress.

:)

I knew it was bad because I had checked it before with the same method you mentioned. Once I replace the dashpot, I'll readjust the secondary opening rate. I'm glad I'm making progress too, I was really getting tired of taking that Q-Jet apart, lol.