frustrated - quadrajet issues

[mistaake]

ok so when i bought the truck it ran really well. except for an intermittent stall out when going over a bump. it was a fuel issue because it would sputter out and then just need a lot of cranking to start again and it would blow a ton of smoke out. so the theory was the float was getting stuck.

i opted to get a refurbished replacement carburetor from a well reputed member her instead of having my old one rebuilt locally, because honestly it's hard to find a shop that knows how to fix a carb around here in 2016.

upon attempting to install the new carburetor i could not get the truck to run/start. in the same parking lot as i was working on the truck in was an auto repair shop that had a big sign out front that they specialize in classic cars. perfect!

well, they charged me an hour labor to adjust the carburetor to the point at which the truck would run but really, really badly. like not even driveable. they claimed the carburetor was defective.

i doubted it and had it towed to my regular shop that i go to. they agreed the new carburetor was defective, and charged me $300 to rebuild my original one.

when i first got the truck back it would die at idle in gear with ac on. they adjusted idle. i drove it for a few days and it seemed to idle and drive ok. except for two issues:

1. in the mornings when its cold it wont run/stay running. mashing on the gas to get it to warm up even for like 5-10 minutes (sorry neighbors) didn't help. if i wait until the afternoon when ambient temperature is warm it was running fine.

2. even though it idled and sounded fine, it seemed a bit down on power. this thing is not fast and neverh as been but it just seemed slower than before.

well, a few days later i was driving in traffic and suddenly it just starts to run absolutely terrible. it started idling really high and just running and sounding awful. i drove it home like but that was not a fun drive.

so that's where we are at now. what's really frustrating is that before all this it ran great except for the intermittent stalling issue.

what the heck do i do??? the seller of the remanufactured carburetor i purchased online has agreed to give me a refund should i send it back but honestly i'm wondering if that carburetor is a-ok and something else is causing my issue? though me and two shops just couldn't get that carburetor to work.

any advice and suggestions appreciated. i'm at the point where i want to sell the truck for parts and just move on to a project with fuel injection but if it was running right i really do like the old suburban :'(

 

[Green79Scottsdale]

Have you checked if your distributor is tightened down? If it is loose and moving around, a large bump (like a speed bump) has the potential to throw off the timing. Timing being off could possibly account for the hard starting, high idle, loss of power, and running and sounding awful.

Check that your distributor is tight and that it set to the correct initial timing. Gotta start somewhere...

 

[mistaake]

Have you checked if your distributor is tightened down? If it is loose and moving around, a large bump (like a speed bump) has the potential to throw off the timing. Timing being off could possibly account for the hard starting, high idle, loss of power, and running and sounding awful.

Check that your distributor is tight and that it set to the correct initial timing. Gotta start somewhere...

thanks, but initially after it would "stall" after lots of cranking it would run like **** for a few seconds and then it would smooth out to normal again.

i will check the distributor again though to be sure. i don't know if it's set "correct" but unless me leaning on it to change carburetor messed it up it should have been untouched.

 

[1987 GMC Jimmy]

What became of your fuel system overhaul? Did you keep a mechanical pump, and is it pumping okay? Did you end up dropping your tank and washing it out. I did that when I got my Quadrajet rebuilt, and even though I let the tank dry for a while, I still put a treatment of Heet in the gas tank as precautionary water removal. I'm not too familiar with California emissions, but does that thing have an EGR on it because that may be worth looking into if it does. Hell, I would go through the whole emissions system and make sure no vacuum leaks are present because those can be performance killers on a more complex catalyst. I've heard it said that a lot of times carburetor problems have nothing to do with the carburetor. I'm not a veteran mechanic by any means, but my experiences support the conjecture. I would look seriously into the ignition system just to make sure that it doesn't have any gremlins. Make sure the plug wires aren't damaged, and inspect the cap and rotor. You can pop it all off real quick and while you're there you can test the coil with a multimeter (I've seen YouTube videos on the GM HEI ignition coil test parameters), and you can take your Ignition Control Module to be tested at an auto parts store. I think if you have good, clean fuel getting to the carb, a tip top emissions system, and a well functioning ignition system, you can default to the carburetor. Which it could very well be the carb, and even though it's vexing that you've had issues with two of them, I'm just trying to give you other areas to explore. Hope you get it fixed soon.

 

[mistaake]

What became of your fuel system overhaul? Did you keep a mechanical pump, and is it pumping okay? Did you end up dropping your tank and washing it out. I did that when I got my Quadrajet rebuilt, and even though I let the tank dry for a while, I still put a treatment of Heet in the gas tank as precautionary water removal. I'm not too familiar with California emissions, but does that thing have an EGR on it because that may be worth looking into if it does. Hell, I would go through the whole emissions system and make sure no vacuum leaks are present because those can be performance killers on a more complex catalyst. I've heard it said that a lot of times carburetor problems have nothing to do with the carburetor. I'm not a veteran mechanic by any means, but my experiences support the conjecture. I would look seriously into the ignition system just to make sure that it doesn't have any gremlins. Make sure the plug wires aren't damaged, and inspect the cap and rotor. You can pop it all off real quick and while you're there you can test the coil with a multimeter (I've seen YouTube videos on the GM HEI ignition coil test parameters), and you can take your Ignition Control Module to be tested at an auto parts store. I think if you have good, clean fuel getting to the carb, a tip top emissions system, and a well functioning emissions system, you can default to the carburetor. Which it could very well be the carb, and even though it's vexing that you've had issues with two of them, I'm just trying to give you other areas to explore. Hope you get it fixed soon.

i ended up leaving the rest of the fuel system alone because i pumped some fuel out into a clear container by cranking the engine while i had the carb removed and it looked very clear.

i still don't believe its an electrical issue because if i crank the engine long enough it comes back to life. any thoughts on this? it's at the shop right now and they just don't know where to look. could an egr issue cause it to stall and or run like crap intermittently? thank you...

 

[Green79Scottsdale]

i still don't believe its an electrical issue because if i crank the engine long enough it comes back to life. any thoughts on this? it's at the shop right now and they just don't know where to look. could an egr issue cause it to stall and or run like crap intermittently? thank you...

Mechanical choke on this carb? Are all the linkages working freely and properly? I ended up rebuilding my carb a couple of summers ago because the choke was not working properly. Mine was kinda acting like yours. First it took a while to get it going, then it just stopped starting all together.

 

[Georgeb]

Mentioning the choke got me thinking. Can the choke close by lifting the high idle cam? If so, could the bump issue be the choke being closed by the high idle cam thus flooding it out? Its a stretch....

 

[1987 GMC Jimmy]

i ended up leaving the rest of the fuel system alone because i pumped some fuel out into a clear container by cranking the engine while i had the carb removed and it looked very clear.

i still don't believe its an electrical issue because if i crank the engine long enough it comes back to life. any thoughts on this? it's at the shop right now and they just don't know where to look. could an egr issue cause it to stall and or run like crap intermittently? thank you...

Well, if the stream was nice and strong, I think you can rule out the fuel system up to the carburetor. At the present time, are your cold starts better than your hot starts? When tired Ignition Control Modules overheat, they'll have a hard time starting, or they won't start at all. I know you said you didn't think it was electrical. I'm just trying to keep an open mind. I don't think anything in your emissions system on a seventies or eighties non-computerized vehicle affects how the engine runs more than the EGR. When they get really bad, the vehicle will run erratically, especially going down the road. It can start up fine, start driving, but start bogging and slowing down within minutes of leaving where you were. And within seconds you're on the side of the road. I will say that in my experience, a restart with a bad EGR went better than yours, but the shoe fits on everything else. It just ran and drove like ****. I thought about the choke stuff, too, but it's hard to believe you've gotten results this poor with two different carburetors. As far as your issue with the long crank time goes, there are several issues that cause this. Potentially, the ICM, a weak fuel pump, improper choke settings (credit to my forum peers), a fickle pickup coil, and various internal carb issues, of course. Have you tried started it up to get the gasoline flowing, shutting it off after a few minutes, and looked down into the carburetor while actuating the throttle to see if you get two good little streams of gas? This can likely rule out all your worries about the carb innards making the vehicle run poorly. Maybe inefficiently when you get it running right, but that's for later.

 

[mistaake]

Well, if the stream was nice and strong, I think you can rule out the fuel system up to the carburetor. At the present time, are your cold starts better than your hot starts? When tired Ignition Control Modules overheat, they'll have a hard time starting, or they won't start at all. I know you said you didn't think it was electrical. I'm just trying to keep an open mind. I don't think anything in your emissions system on a seventies or eighties non-computerized vehicle affects how the engine runs more than the EGR. When they get really bad, the vehicle will run erratically, especially going down the road. It can start up fine, start driving, but start bogging and slowing down within minutes of leaving where you were. And within seconds you're on the side of the road. I will say that in my experience, a restart with a bad EGR went better than yours, but the shoe fits on everything else. It just ran and drove like ****. I thought about the choke stuff, too, but it's hard to believe you've gotten results this poor with two different carburetors. As far as your issue with the long crank time goes, there are several issues that cause this. Potentially, the ICM, a weak fuel pump, improper choke settings (credit to my forum peers), a fickle pickup coil, and various internal carb issues, of course. Have you tried started it up to get the gasoline flowing, shutting it off after a few minutes, and looked down into the carburetor while actuating the throttle to see if you get two good little streams of gas? This can likely rule out all your worries about the carb innards making the vehicle run poorly. Maybe inefficiently when you get it running right, but that's for later.

nah it's the cold starts that are damn near impossible. warm starts are instant except when it stalls out due to going over a bump just the right way.

we definitely have to investigate the choke issue. that is an excellent point. if the choke closes suddenly could it cause it to flood & stall?

i appreciate the input so far. the shop still seems to have no idea wtf to do to fix my truck :/

 

[theblindchicken]

Not sure if you've done this already, but check your plugs.

Fouled plugs will cause a great loss of power plus a low idle. If combined with a fuel-air ratio that is off, you've got plugs that are barely firing trying to burn fuel that isn't at the correct mixture. So you'd only be burning a portion of a part of the mixture.

The cold start could be due to the much denser air that throws the mixture off enough to make starting harder.

 

[mistaake]

Thank you everybody for your input.

The shop "adjusted the floater inside the carburetor to lower the amount of fuel that goes in" and so far so good.

it does run-on/diesel a little bit once in a while and cold starts still aren't as good as it used to be when i got it but it's definitely driveable now.
@theblindchicken, i definitely have to do plugs and wires. new acdelco plugs and omnispark wires are in my possession. i think this will help it run better. they are probably fouled from all the flooding and messing with carburetors.

so far it hasn't stalled and i've driven it for a few days now but if it does it again we have to explore additional options. so far so good thoguh *knock on wood*