06-14-2015, 08:26 PM | #1 |
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Starting issue
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? |
06-14-2015, 08:53 PM | #2 |
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Re: Starting issue
If carb, timing adjusting right - it should fire up quickly. Check vacuum/leaks.
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06-14-2015, 09:27 PM | #3 | |
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Re: Starting issue
Quote:
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.
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06-14-2015, 09:44 PM | #4 | |
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Re: Starting issue
Quote:
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06-14-2015, 10:20 PM | #5 |
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Re: Starting issue
How long does it 'stumble' off the line after running?
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06-14-2015, 10:29 PM | #6 |
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Re: Starting issue
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06-15-2015, 07:02 AM | #7 |
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Re: Starting issue
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...
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06-15-2015, 08:10 AM | #8 |
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Re: Starting issue
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.
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06-16-2015, 11:22 PM | #9 |
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Re: Starting issue
The fuel seems to have a delay in the spraying. How do you adjust the carb pump?
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06-17-2015, 07:26 AM | #10 |
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Re: Starting issue
do u have a phenolic carb spacer?
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06-17-2015, 02:29 PM | #11 |
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Re: Starting issue
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06-17-2015, 02:35 PM | #12 |
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Re: Starting issue
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.
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
06-17-2015, 02:36 PM | #13 | |
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Re: Starting issue
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06-17-2015, 04:24 PM | #14 |
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Re: Starting issue
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.
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06-18-2015, 06:15 AM | #15 | |
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Re: Starting issue
Quote:
(adjustment examples) 1. choke setup 2. air/fuel mixture 3. accelerator pump adjustment Need more info... |
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06-18-2015, 12:39 PM | #16 | |
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Re: Starting issue
Quote:
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. |
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06-18-2015, 01:17 PM | #17 | |
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Re: Starting issue
Quote:
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06-18-2015, 01:21 PM | #18 | |
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Re: Starting issue
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06-18-2015, 01:38 PM | #19 |
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Re: Starting issue
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06-18-2015, 03:40 PM | #20 |
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Re: Starting issue
Once idling, how much vacuum does the engine pull? These carbs are very vacuum sensitive.
Regards, Mike
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06-18-2015, 05:46 PM | #21 |
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Re: Starting issue
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06-18-2015, 08:16 PM | #22 |
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Re: Starting issue
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...
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06-20-2015, 01:19 PM | #23 |
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Re: Starting issue
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? |
06-20-2015, 01:59 PM | #24 |
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Re: Starting issue
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.
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06-20-2015, 02:10 PM | #25 | |||
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Re: Starting issue
Quote:
Quote:
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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.
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I own 3 classic vehicles. 1971 LWB C10 Deluxe. 1974 VW Super Beetle. 1971 VW Fastback. The C10 and the Super Beetle run, the Fastback is just not there yet! Please visit my Super Beetle and Fastback profile on TheSamba. |
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