Dying at stop lights
07-19-2013, 12:28 PM
#1
Racer
Thread Starter
Dying at stop lights
I just got my car back from the paint shop, but I am I having some (I believe) carb issues.
The car will idle just fine when sitting, and initially when driving. After about 10-15 minutes of driving, it will die when I stop at an intersection. It fires right back up, and really wants to take off.
I have a 1973 Corvette with a 350 with a TH400, and an Edelbrock 600CFM carb.
I believe my carb might be hooked up wrong. The drivers side vacuum is hooked up to the tach, and the passenger side is sealed. I believe the trans is hooked to the intake manifold (need to check), but it is shifting through the 3 gears I have (early I think - in 3rd at 15-18 mph for sure).
According to Edelbrock, the passenger side vacuum needs to be hooked to the distributor (for emission controlled vehicles, which mine is not), and the drivers side vacuum goes to the transmission.
Please help!
The car will idle just fine when sitting, and initially when driving. After about 10-15 minutes of driving, it will die when I stop at an intersection. It fires right back up, and really wants to take off.
I have a 1973 Corvette with a 350 with a TH400, and an Edelbrock 600CFM carb.
I believe my carb might be hooked up wrong. The drivers side vacuum is hooked up to the tach, and the passenger side is sealed. I believe the trans is hooked to the intake manifold (need to check), but it is shifting through the 3 gears I have (early I think - in 3rd at 15-18 mph for sure).
According to Edelbrock, the passenger side vacuum needs to be hooked to the distributor (for emission controlled vehicles, which mine is not), and the drivers side vacuum goes to the transmission.
Please help!
07-19-2013, 08:23 PM
#2
There is nothing wrong with having the transmission vacuum line connected to the intake manifold. Concerning the other two connections on the carburetor, the one that has vacuum at idle should be connected the the distributor and the other one sealed.
07-19-2013, 10:20 PM
#3
Melting Slicks
I had the same problem with my '73 - 350 SB with Holley 650 Double Pumper & TH400. Wish I could tell you for sure what fixed it but I did so many things, I'm not sure. Here's the story.
The previous owner started having this problem shortly after advertising the car for sale. He was frustrated when I showed up to look at it because of the problem. I bought the car anyway and we rebuilt the carb in his garage before I drove it from Arizona back to Texas. The rebuild improved things slightly but did not solve the problem.
After getting the car back home, I discovered the fuel pressure to the carb was too high and I had one float that was leaking. Fixing these issues did not solve the problem.
Took the car in for a dyno tune. They rejetted the carb and did some other things. Ran much better after getting it back and the problem seemed to go away at first but eventually returned intermittently.
Went on a crusade to check for vacuum leaks. Re-torqued the intake, carb, valve covers, etc. Checked for vacuum leaks everywhere. Adjusted the carb again. Checked the float levels. Again the problem went away but not for long. I became adept at giving the engine a bit of throttle while braking to keep the idle high and prevent the dying at stops.
On my last road tripped, the car kept trying to die when I came to a stop in each town along the way. It ran fine on the highway but I had to play with the throttle to keep it from dying at stops in town.
If I just drove around town, I didn't seem to have the problem nearly as much. It sure seemed more prevalent after highway driving.
Finally decided to replace the double pumper carb with a Holley Street Avenger vacuum secondary carb. While doing that I made the time to check many other things. I discovered the wrong PCV valve had been installed and found a more correct one. I discovered the carb bolts were loose again. Because the problem seemed to happen more frequently when braking hard, I double checked the brake booster setup. I found the brake booster vacuum line had been reduced from 3/8" to 1/4" hose and teed into another line before tying into the intake vacuum port. I replaced that hose with all 3/8" and connected it to the proper fitting on the new carb while also replacing the check valve at the brake booster. I redid all vacuum lines in the engine compartment and made sure I had no leaks. I discovered my distributor had too much end play and so I pulled and shimmed it accordingly. My vacuum advance was connected to port vacuum and I switched it to manifold vacuum which my engine likes better. I studied Lars' papers and set up the new carb on the bench according to his instructions. After installation, I set the timing according to Lars' papers. I did not have to adjust the carb after installation. Lars' jet specs and setup instructions were perfect.
Car runs better than ever and the dying at stops problem is gone. Still don't know for sure what I did to solve it. Maybe it took all of the above. Just speculating here but I think the brake booster vacuum line not being correct and possibly having a bad check valve could have played a role in the problem. Getting the engine tuned better than ever boosted the vacuum at idle which may have helped as well. But, it may have just been the carb. Had problems with it constantly and finally realized I didn't need a racing carb for the street. Very happy with the Street Avenger.
Hope this helps some.
DC
The previous owner started having this problem shortly after advertising the car for sale. He was frustrated when I showed up to look at it because of the problem. I bought the car anyway and we rebuilt the carb in his garage before I drove it from Arizona back to Texas. The rebuild improved things slightly but did not solve the problem.
After getting the car back home, I discovered the fuel pressure to the carb was too high and I had one float that was leaking. Fixing these issues did not solve the problem.
Took the car in for a dyno tune. They rejetted the carb and did some other things. Ran much better after getting it back and the problem seemed to go away at first but eventually returned intermittently.
Went on a crusade to check for vacuum leaks. Re-torqued the intake, carb, valve covers, etc. Checked for vacuum leaks everywhere. Adjusted the carb again. Checked the float levels. Again the problem went away but not for long. I became adept at giving the engine a bit of throttle while braking to keep the idle high and prevent the dying at stops.
On my last road tripped, the car kept trying to die when I came to a stop in each town along the way. It ran fine on the highway but I had to play with the throttle to keep it from dying at stops in town.
If I just drove around town, I didn't seem to have the problem nearly as much. It sure seemed more prevalent after highway driving.
Finally decided to replace the double pumper carb with a Holley Street Avenger vacuum secondary carb. While doing that I made the time to check many other things. I discovered the wrong PCV valve had been installed and found a more correct one. I discovered the carb bolts were loose again. Because the problem seemed to happen more frequently when braking hard, I double checked the brake booster setup. I found the brake booster vacuum line had been reduced from 3/8" to 1/4" hose and teed into another line before tying into the intake vacuum port. I replaced that hose with all 3/8" and connected it to the proper fitting on the new carb while also replacing the check valve at the brake booster. I redid all vacuum lines in the engine compartment and made sure I had no leaks. I discovered my distributor had too much end play and so I pulled and shimmed it accordingly. My vacuum advance was connected to port vacuum and I switched it to manifold vacuum which my engine likes better. I studied Lars' papers and set up the new carb on the bench according to his instructions. After installation, I set the timing according to Lars' papers. I did not have to adjust the carb after installation. Lars' jet specs and setup instructions were perfect.
Car runs better than ever and the dying at stops problem is gone. Still don't know for sure what I did to solve it. Maybe it took all of the above. Just speculating here but I think the brake booster vacuum line not being correct and possibly having a bad check valve could have played a role in the problem. Getting the engine tuned better than ever boosted the vacuum at idle which may have helped as well. But, it may have just been the carb. Had problems with it constantly and finally realized I didn't need a racing carb for the street. Very happy with the Street Avenger.
Hope this helps some.
DC
07-21-2013, 05:51 PM
#4
Racer
Thread Starter
Update, my manual choke is not set up, see pic below:
When the butterflies are closed, the engine shuts down. Possibly the problem? Any suggestions or help is appreciated.
When the butterflies are closed, the engine shuts down. Possibly the problem? Any suggestions or help is appreciated.
Last edited by Killingsworth 73; 07-22-2013 at 01:21 PM.
07-21-2013, 09:08 PM
#5
Safety Car
Your secondary's are opened by the throttle and vac but there will be linkage from the choke, to prevent the secondaries from opening until the choke is completely open.
If you choke is closing after its warmed up, that'll kill the motor or a bad fuel pump. Judging from you questions, you're still learning your way around a carb. Take your time and do some research! Then come on and ask alot of questions
If you choke is closing after its warmed up, that'll kill the motor or a bad fuel pump. Judging from you questions, you're still learning your way around a carb. Take your time and do some research! Then come on and ask alot of questions
07-21-2013, 09:16 PM
#7
Racer
Thread Starter
Looks like it in the pic, but I don't think so. It will drive fine when you have a little throttle, but dies when I come to a stop. I can cruise 70 on the highway just fine.
Also, it is dying with the air filter removed also... In the driveway, not driving it like that.
Also, it is dying with the air filter removed also... In the driveway, not driving it like that.
Last edited by Killingsworth 73; 07-21-2013 at 09:19 PM.
07-21-2013, 09:18 PM
#8
Racer
Thread Starter
Your secondary's are opened by the throttle and vac but there will be linkage from the choke, to prevent the secondaries from opening until the choke is completely open.
If you choke is closing after its warmed up, that'll kill the motor or a bad fuel pump. Judging from you questions, you're still learning your way around a carb. Take your time and do some research! Then come on and ask alot of questions
If you choke is closing after its warmed up, that'll kill the motor or a bad fuel pump. Judging from you questions, you're still learning your way around a carb. Take your time and do some research! Then come on and ask alot of questions
