I have now owned my first Corvette, a 1976 L82, for three years. In this time a couple different places have worked on my car fixing various things. However, problems still remain. I am not a mechanic, unfortunately. I wish i was. I am only a Corvette fan. I am desperately looking for some help.
Here's the problems:
1) starting. When the engine is cold, it takes quite a lot of pumping the gas pedal and cranking to get started.
2) Stalling when hot. After running for a while down the highway, the engine is heated up. Then stopped at a light, in drive, the RPMs drop and the the engine stalls. Trying to restart is VERY hard. When at the light, I now usually put it in neutral, which keeps the RPMs above 700 and does a good job of preventing the stall. When in drive and stopped, the RPMs drop to 500 and then stall.

After reading many post here on the forum, it seems that this may be a carb problem. I really could use some local help here in the Detroit, Michigan area.

I would really like to participate in this year's Woodward Dream Cruise in August, but cannot unless this gets fixed. No one wants to have their call stall in the middle of a cruise. ugh.

Help/advised is much appreciated.

 

Could this be as simple as properly setting the choke for start ups and adjusting the idle speed screw for warm?

Been a while since I've had a quadrajet... Back in my younger days I used to call em quadra-puke 's... Lol. Used to love the sound of those secondaries opening up!

By no means am I a carb expert, I just remember tinkering with mine a lot... But it has been a while... There could be other issues besides carb, but idle screw, and choke adjustment are the first places I'd start looking into... Just from the symptoms provided...

 

Oh... And might look into timing chain slop... Had a engine back in the day with a stretched timing chain... Would run great at an idle in park or neutral... Then die when I put it in gear... The chain would allow the timing to change under load and it would ALWAYS kill the car once in gear... I could power-brake it to keep the Rpms up and drive it around... But it HATED to idle in gear...

 

Ok. Sounds good. I will need to find some local help to look into those areas. So many "kids" these days in shops only know how to hook up a car to a computer for diagnosis. I need someone with real old school knowledge.

 

Good luck finding someone knowledgeable. I think that some proper adjustments will probably solve your problems. It may be a combination of age, improper settings and today's crappy gas.

 

Replace it with a Holly Street Avenger 570 cfm.
Did that on my '75 and have had no trouble.

 

Had a similar problem with my Q-jet. Would have a terrible time trying to get the thing to start, turned out the PO put in the wrong fuel filter that was too long and crushed inside the housing preventing fuel from entering the carb. Mine would also stall when it got hot, and be impossible to get started again. Thought it was vapor lock or something, until I took the air cleaner lid off and saw fuel pouring down the carb with the engine off. Thankfully Q-jets are easy to work on and you only have to take the top plate off to replace the float (which was my problem) Either way I'm almost positive it's time to rebuild your Q-jet

 

For the first problem, try cranking the motor for a few seconds, stop, then give the gas pedal one smooth depression to the floor. Release and try starting it.

For the second problem, I'd imagine you have a vacuum leak on the other side of one of the TVS units(thermal vacuum switch). I'd start by capping the sources and start adding them back until you find where the problem is reproducible. You could also look at a manual for your model year and determine how they're supposed to behave, and test them with a vacuum pump. You could also remove them and test them on a stove.

The QuadraJet itself typically does not have problems that appear after warming up. May be worth while to loosen the choke up and see if the second problem is reproducible. It could be that someone did the idle adjustments with a partially closed choke and once the car fully heats up the base idle is not enough to keep that L-82 running. Those heated chokes can be lazy, especially if the springs are worn out, and this could cause someone to tune what they think is the fast idle while the choke is actually still active.

 

People who didn't grow up in the 50, 60, 70's. ,......most flat don't understand how a carb works or how to start a carb equipped car.

If you want a mindless woman's car...buy a Honda civic or Toyota.....or a new Corvette any secretary can drive while doing her makeup.

It's so simple ....a six grader could learn to drive farm tractors. Our country is a bunch of sissy helpless idiots. And they did .....base knowledge to live by .

Everything is done for people today ..push a button and it starts. Corvettes use the same tech from WWII , points and carbs . It doesn't get much easier. Go back...and next step back is horse and buggy.....

There is nothing wrong with your car......but you ....sit down and noodle it out think about how it works .....there are picture books even

Learn how to start the damn thing ......think about how it works .....there is no damn electric fuel pump.

Even my mother a total none mechanical minded woman could start and choke the engine , understood priming by turn it over a few tines. Wait a few seconds for the gas to get into the engine turn the key and feather the engine as necessary.

If you can't do this .....please go ride a bicycle or take a taxi......and there are short buses too..if that's too complex.

Q jets are super reliable

Just dummies that don't want to read a few pages of Lars instructions.

 

Wow. Talk about uncalled for. The guy is asking for help and all you can offer is pointless insults? Plus, clearly there is a problem with the car, not his methods.

As for the OP, don't go and buy a Holley 570 or any other one for that matter. That would be a downgrade in my opinion. Yours just needs some attention.

 

Q-Jets can be messed up. In fact most rebuilds are...
And hard starting, due to fuel evaporation is all-too common.
And fuel can siphon back to the tank, draining the fuel bowl. Check that filter!
Shark Racer has offered top-notch advice. Others will chime in.
Don't listen to the negative detractors around here.
Good luck with your Vette and have fun.

 

You can learn how to work on that carb. Many people say they are not mechanics. It might be because they haven't been given the proper information on how to work on what they have.

A q-jet can be adjusted with basic tools. but you have to know what you are looking for and how to go about it.
This book explains it all;

Read it. study it. Read it again. Absorb what is in this book and you will know how that carb works. You will be amazed what you can do with it.
Good luck, and come back and ask questions about the stuff you just can't wrap you head around.

 

Contact Lars Grimsrud at v8fastcars@msn.com. Inquire about a copy of his QuadraJet papers. If you can't or don't want to tackle the job he can also make your QuadraJet look and run like new. He fixed mine and I couldn't be much happier. Very reasonable price for his services, too. I highly recommend him.

 

Lots of good info here so far.

1) search for the Lars docs and have a read - may look daunting but the quadrajet is actually a very simple and reliable carb choice.

2) while the car sits often the fuel in the float can evaporate so crank the car for a while to get fuel in the bowl first before pumping it a few times. It should then start ok.

3) check the accelerator pump is working properly - after cranking the car look in the carb and ensure you can see 2 strong shots of fuel each time you hit the accelerator - a weak of non functional one will make starting a real pain.

4) check for vacuum leaks, unplugged ports, cracked rubber plugs etc etc and see if you can ensure no leaks - it makes so much of a difference as the carb uses vacuum and air flow to work properly.

5) check the actual choke is working. On a cold start a press of the pedal before doing anything and make sure it is closed - it needs to restrict air flow to start when cold.

6) if you still get no where start thinking about a rebuild on the carb its easier then you may think - look here http://forums.corvetteforum.com/c3-g...ourney-35.html

Good luck mate, its all part of the journey.

 

You've got some great advice here. I just rebuilt my Q-Jet for the 81 a few weeks ago. I took my time, read the books and all in all it was a fairly strait forward job. If you go this route buy cliffs book, identify the tools you'll need and get those before jumping in. My rebuild took 2 weeks because I had to stop to find the tiny drill bits needed. I still haven't tuned it to perfection yet as I'm finishing my headers install, once I get the new exhaust hung I'll complete the tune. But even after the rebuild without a solid tuning the car was a ton more responsive!

1) floor the pedal and release slowly. The choke should close, ensure it does. If not adjust accordingly

2) set your fast idle speed (passenger side of the carb) with the engine cold. I believe the book calls for around 1500 rpm?

3) set your idle screw (driver side of the carb) After the car warms up (closed loop) be sure the choke pull off has disengaged the code (butterflies open)

4) get a dwell meter to make the above adjustments! I got one from sears in Stock for around $35. It has the dwell, tach and charging on it. This ensures you are setting the dwell and tach precisely. It seems to me that your rpm is set a little low if it's dropping to 500.

5) check for vacuum leaks on the carb.

How some of this helped

 

Ditto on Lars info. In general you probably are faced with three or four simple problems, but you must start and look at each individually. 1) If it has been several years since the carb has been into, you need to replace the float with the right OEM type float. These will saturate with gas over time and remember that ethanol is not your friend. 2) Change the filter too. 3) the accelerator pump is made of a rubber compound that may have hardened with time and heat from the engine, change it too 4) you need to check and reset your air/idle jets. Again ethanol has less BTU's so these should be tweaked. 5) now set the engine idle to 600-650 in drive. You will find that these carbs are no longer produced, but you can still buy most of the parts from Eldebrock at your local parts houses.

These are very good carbs if they haven't had bubba working on them. Again check with Lars, he can fix it if bubba was a past mechanic.

 

YOU ARE A DICK....if I get kicked off this forum...I guess that is how it goes. This is only the third time I have been on here...just looking for some tips on my C3 I am having issues with and I come across this. The whole point of a forum (even if you are good with cars) is to look for help when in a pinch. If you are an armchair critic on a powertrip to make yourself feel better about you and your prowess as a car God, you don't need to be on here. Why'd you join if you know everything? So the point is...if ya don't like it...get the **** off it. I'd say more but that's good enough. Whew...I feel better.

 

 

The original post is over a year old, maybe the negative nellies have repented by now! Let's hope so.

 

Good info...I need to print a few of these post for future reference.

Brian