The 78 K5 350 4BL quadrajet starts up no problem from cold. Just one pump of the gas peddle and it starts right up. Right at start up it is running at about 1700 rpm.
CK5
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How soon after startup should the carb go from fast idle to idle? 78 4Bl qjet
- Thread starter wazzabie
- Start date
Depending on ambient temperature. 1 to 3 minutes. Should drop down to 2nd step, the first time the pedal is snapped.
Perhaps I was not patient enough.
What should I do to fix the cold start from hanging at 1700rpm?
After 1-3 min I snap the peddle and the cold start idle does not drop from 1700rpm. The outside temp is in the 70s. I took off the air cleaner and found the fast idle cam in a lower position. I manually move the thermostatic rod, fast idle cam and choke valve. I then restart the K5 and I'm at 850rpm.
What should I do to fix the cold start from hanging at 1700rpm?
Check the spring in the heat stove. Make sure the rod is connected ea end.
The vacuum break should be fully retracted when engine is running.
There is a little arm I the carb body, you can look down along the choke butterfly rod and see it, small light helps. Can be a pita to get the rod 90° in the hole. If the rod is not properly installed the choke butterfly will flop around loosely
The vacuum break should be fully retracted when engine is running.
There is a little arm I the carb body, you can look down along the choke butterfly rod and see it, small light helps. Can be a pita to get the rod 90° in the hole. If the rod is not properly installed the choke butterfly will flop around loosely
I've been playing around with the carb some more. From cold start the fast idle cam is fully up which is expected and rpms are at 1700. When I tap the gas after a few moment the fast idle cam goes down but not fully. I have to manually move the fast idle cam down and then the engine will run at 700-900 rpm. I checked the vacuum line from the distribitor to the carb. That vacuum line is good. The heat stove rod is connected on both ends.
The second step which is where it should be after first snap should last the longest. I sometimes have to snap the throttle a couple times,waiting @30 seconds between
Check for linkage and butterfly free movement, and lube the heck out of everything linkage related. I used to set my cold idle speed when the engine was warmed up, not when it was a first cold start up. Engine would start great cold, and run at 12-1300 for a minute or so, but if I wasn't there to kick it after a couple minutes it would reach the 1500 rpm cold high idle speed As the choke opened up.
Vac break (Choke Pull off) is what allows the initial kick down and opens the choke about 3/16 when started. After that the choke spring needs to unwind letting the choke open and through the linkage allowing the fast idle cam to drop further.
Check and see if it holds vacuum. Like was said should be retracted when running.
Fast idle cam could be stiff needing a shot of lube.
Check and see if it holds vacuum. Like was said should be retracted when running.
Fast idle cam could be stiff needing a shot of lube.
Here is a good video I found showing how the choke should function at startup. At 4:22 you can see how quickly the vacuum break assembly pulls on the rod. I'm going to see if my vacuum break assembly is working.
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My vacuum break assembly is working. Its when I tap the gas after startup the high idle cam does not completely fall down. I sprayed some wd40 on the linkages and it still hangs. Maybe I need to bend the rod from the choke spring? I installed a new manifold to carb gasket which may have been thicker.
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It should take a minute or 2 before the idle drops again. Another minute before it goes all the way to curb idle.
The heat stove coil is what needs to pull the linkage down.
If the intake cross over has been blocked or the passage is Carboned up, it will take much longer for the coil to warm up.
The heat stove coil is what needs to pull the linkage down.
If the intake cross over has been blocked or the passage is Carboned up, it will take much longer for the coil to warm up.
Lots of good info Delco Manual Covers the different models.
Adjustments should be the last thing. You do.
Is it ok to put the K5 into drive when the idle is at 1700 rpm?
My big block was hanging at high idle also. I think I ended up just turning the fast idle screw down since it would still warm up ok and I don't drive it very much. Pretty much the same problem though, my linkage just wouldn't drop all the way when I snapped the throttle. Might go over this thread and see if I can fiddle with it some more.
Not ideal, be sure your foot is pushing the brake pedal hard. Depending on your transmission, it can cause a shockload on the drivetrain. Kinda like dumping the clutch on a stick trans.
I think the linkage can be removed while the carb is still on the engine. I have a spare carb that I'm going to swap linkage with to see if this is the problem. I'll swap out the fast idle cam and other related parts.
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If you pull the assembly off the side of the carb you may have trouble lining up the choke arm inside the carb while still in the engine. Just a word of warning.
It's no fun but it can be done
So best to take the carb off the engine?
