Starting issue

[kool1972]

My last post was with the carb not working right. Now that I have that fixed I have issues starting the truck. Here are the details....

1972 c20 402 big block.
Timed 13 degrees intial
New q-jet carb
New Accell HEI dizzy

I have to pump the throttle many times to get it to start. Can't just turn the key and it start it away. But that's what I am hoping for. Once started I have a slight stumble off the line.

Any ideas?

[litew8]

If carb, timing adjusting right - it should fire up quickly. Check vacuum/leaks.

[davepl]

Originally Posted by kool1972

My last post was with the carb not working right. Now that I have that fixed I have issues starting the truck. Here are the details....

1972 c20 402 big block.
Timed 13 degrees intial
New q-jet carb
New Accell HEI dizzy

I have to pump the throttle many times to get it to start. Can't just turn the key and it start it away. But that's what I am hoping for. Once started I have a slight stumble off the line.

Any ideas?

You have the choke, choke door, choke pull-off rod, choke pull-off canister, heat riser, crossover tube, heat stove, thermac, and stove pipe installed with the factory snorkel air cleaner?

If not, stop reading, I can't help on crippled ones missing parts.

If so, you will always need to pump it 2-3 times when cold to set the choke and prime the engine via the accelerator pump in the carb. When warm, you should not have to do anything.

[kool1972]

Originally Posted by davepl

You have the choke, choke door, choke pull-off rod, choke pull-off canister, heat riser, crossover tube, heat stove, thermac, and stove pipe installed with the factory snorkel air cleaner?

If not, stop reading, I can't help on crippled ones missing parts.

If so, you will always need to pump it 2-3 times when cold to set the choke and prime the engine via the accelerator pump in the carb. When warm, you should not have to do anything.

Yes. I have all of that. But I still have to pump more than 2-3 times. More like 6-7

[litew8]

How long does it 'stumble' off the line after running?

[kool1972]

Originally Posted by litew8

How long does it 'stumble' off the line after running?

Just at first. Then it seems to run fine. It's the very first part of pressing the throttle that gives me problems.

[7tee]

Originally Posted by kool1972

Just at first. Then it seems to run fine. It's the very first part of pressing the throttle that gives me problems.

At the same time (with the motor off), look down inside of carb as you move the throttle arm to determine if the fuel spray is coming out as you just move the throttle arm, you may need to adjust the carb pump to achieve this...

[jjzepplin]

As above it could be your accelerator pump adjustment. My OLD 2 barrel had a scored pump cylinder and once fixed I had to put in a "BLUE" pump diaphragm for the new fuels today and the adjust to find the "SWEET" spot. Like new now though. I had rebuilt it using the pump in the kit and it lasted less than a year before it turned to mush.

[kool1972]

The fuel seems to have a delay in the spraying. How do you adjust the carb pump?

[cdowns]

do u have a phenolic carb spacer?

[kool1972]

Originally Posted by cdowns

do u have a phenolic carb spacer?

no I don't. I forgot to mention that when I looked into the carb while turning the throttle. I only got one squirt. not two, if that means anything.


Thank you.

[davepl]

Gotta be the accelerator pump. If it used to work, I doubt it's an adjustment. It's by far more likely that the spring broke so it doesn't return or, even more likely, the rubber diaphragm ripped.

Ten seconds to push out the roll pin, pull it out the top, and have a look. Nothing else (other than the air cleaner I guess) needs to come apart.

And here's a tip: put a little flat screwdriver or something against the area where the roll pin will butt up against when you drive it inwards to release the pump arm. Makes it way easier to pry it back in when you reinstall than if you left it flush up against and can't get anything in there. You can still try with needle nose pliers, but that can scar up the pin.

First time you do it is 10 seconds. Once you've done it before, it's 3.

[kool1972]

Originally Posted by davepl

Gotta be the accelerator pump. If it used to work, I doubt it's an adjustment. It's by far more likely that the spring broke so it doesn't return or, even more likely, the rubber diaphragm ripped.

Ten seconds to push out the roll pin, pull it out the top, and have a look. Nothing else (other than the air cleaner I guess) needs to come apart.

And here's a tip: put a little flat screwdriver or somethign against the area where the roll pin will butt up against when you drive it inwards to release the pump arm. Makes it way easier to pry it back in when you reinstall.

The carb is a fresh rebuild I purchased from a autoparts store.

[Jonlopes]

Unfortunately a rebuilt carb (Especially a quadrajet) does not mean it is dialed in or correct. These carbs are very complicated and are quite difficult for the minimum wage workers to work. The workers probably tear the carb down, dip it in cleaner and build it back up changing the rubber parts, gaskets and anything obviously wrong. I highly doubt they are tested at all.
I work in the temp industry and have staffed a major rebuilder in Torrance, CA in the past.

[7tee]

Originally Posted by kool1972

The carb is a fresh rebuild I purchased from a autoparts store.

Let's start again, so, have you made any adjustments at all to this out of the box Q-jet? What size is it?

(adjustment examples)

1. choke setup
2. air/fuel mixture
3. accelerator pump adjustment

Need more info...

[kool1972]

Originally Posted by 7tee

Let's start again, so, have you made any adjustments at all to this out of the box Q-jet? What size is it?

(adjustment examples)

1. choke setup
2. air/fuel mixture
3. accelerator pump adjustment

Need more info...

no adjustments, I realize now that adjustments need to be made. The more and more I am reading from this site, the more I am aware that I need to do some adjustments. I thought at first that the carb would be good out of the box.

I am not sure what size it is. I got the number off the side of the carb and ordered a new one.

The air/fuel mixture has been adjusted. The accelerator pump has not. That is my next task.

[7tee]

Originally Posted by kool1972

no adjustments, I realize now that adjustments need to be made. The more and more I am reading from this site, the more I am aware that I need to do some adjustments. I thought at first that the carb would be good out of the box.

I am not sure what size it is. I got the number off the side of the carb and ordered a new one.

The air/fuel mixture has been adjusted. The accelerator pump has not. That is my next task.

If the air/fuel mixtures have been set to the highest rpm or vacuum (vacuum is best) then your good there. Readjust your idle speed to around 750 rpm. Looking at your pump arm there are two holes that the linkage rod can go into, IMO you should be in the inside hole (the one closest to the pump). As far as the timing I would be no more than 12*btdc. Hope this helps a little and let us know what works for future reference...

[kool1972]

Originally Posted by 7tee

If the air/fuel mixtures have been set to the highest rpm or vacuum (vacuum is best) then your good there. Readjust your idle speed to around 750 rpm. Looking at your pump arm there are two holes that the linkage rod can go into, IMO you should be in the inside hole (the one closest to the pump). As far as the timing I would be no more than 12*btdc. Hope this helps a little and let us know what works for future reference...

ok. thank you. the pump linkage rod is in the inner hole already.

[7tee]

Originally Posted by kool1972

ok. thank you. the pump linkage rod is in the inner hole already.

Great, with the breather off of carb and engine is running temp, make sure the choke is all the way off and the front butterfly is straight up and down, good luck...

[MagmaJct]

Once idling, how much vacuum does the engine pull? These carbs are very vacuum sensitive.

Regards,
Mike

[kool1972]

Originally Posted by MagmaJct

Once idling, how much vacuum does the engine pull? These carbs are very vacuum sensitive.

Regards,
Mike

where do I hook up my gauge to find that out. manifold vac or carb?

[7tee]

Disconnect the vacuum hose on the carb that comes from the distributor and connect there ( should be manifold vacuum). You will probably have to raise your rpm to keep the idle up while doing this since you disconnected your vacuum advance. Try to keep this idle also around 750 rpm...

[kool1972]

Last night I played with the truck for a little bit. I found that if you push the accelerator pump all the way down nothing happens. I pushed it a few times and nothing happened. I did this with the engine running. Wouldn't his cause the engine to change tune? There is also fuel leaking (seeping) out the shaft of the pump too.

I would say the pump is bad. Correct?

[davepl]

Could you PLEASE pull and check the accelerator pump like I said 10 posts ago? 25 more posts of speculation won't help if you don't actually try the things the users are suggesting.

[MagmaJct]

Originally Posted by kool1972

Last night I played with the truck for a little bit. I found that if you push the accelerator pump all the way down nothing happens. I pushed it a few times and nothing happened. I did this with the engine running. Wouldn't his cause the engine to change tune? There is also fuel leaking (seeping) out the shaft of the pump too.

I would say the pump is bad. Correct?

You're breaking my heart!

Originally Posted by jjzepplin

As above it could be your accelerator pump adjustment. My OLD 2 barrel had a scored pump cylinder and once fixed I had to put in a "BLUE" pump diaphragm for the new fuels today and the adjust to find the "SWEET" spot. Like new now though. I had rebuilt it using the pump in the kit and it lasted less than a year before it turned to mush.

Originally Posted by davepl

Gotta be the accelerator pump. If it used to work, I doubt it's an adjustment. It's by far more likely that the spring broke so it doesn't return or, even more likely, the rubber diaphragm ripped.

I had to go back and re-read the entire thread to get a handle on what's going on. So it starts well now? It idles well? Aside from the off-idle stumble, it runs well?

I think the off-idle stumble just might be the accelerator pump. The quadrajet can be a pain to get back together. I can't remember offhand, but I think once you pull the top, you have to remove the gasket to get to the pump assembly. Someone will correct my if I'm wrong.

The primary metering rods will have to be removed along with the gasket, as they pass through the gasket. There's a plastic-ish ring that's supposed to hold the metering rods' piston in its bore. This often fails to do it's job. Once you are ready to reassemble, after you fish the rods back into their respective jets, use a feeler gauge or thin (clean!) putty knife to hold the meter rod piston in its bore until the carburetor top is seated.

Regards,
Mike

P.S. Consider investing in a text book about these carbs. It'll pay dividends, doing a better job explaining, w/pictures, than what I can do in a forum format.