Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem
Quadrajet runs better without accelerator pump.
73ss:
X2 on the coil resistance.
Have you tried removing the main vacuum hose that feeds the vacuum system and plugging the port? Lots of places for a vacuum leak on a C3, headlight doors & vacuum relays, wiper system, etc.
Maybe you have a hidden vacuum leak and have the idle screw too high to compensate the leak and have too much transfer slot exposed causing a rich condition?
edit: Watched the vid again and it looks like you have it capped off.
quadrajam:
....???..Tough one. Usually the other way around. How bout metering rods too short or hanging
too high.... PP spring way too strong.... No vacuum under power piston...
Reach in through the vent tube with a tiny screwdriver and check that you can push on
the hanger and move the PP up and down. Then check to see that its down at idle.
QJ
NathansCorvette:
--- Quote from: 73ss on November 21, 2024, 01:47:39 PM ---X2 on the coil resistance.
Have you tried removing the main vacuum hose that feeds the vacuum system and plugging the port? Lots of places for a vacuum leak on a C3, headlight doors & vacuum relays, wiper system, etc.
Maybe you have a hidden vacuum leak and have the idle screw too high to compensate the leak and have too much transfer slot exposed causing a rich condition?
edit: Watched the vid again and it looks like you have it capped off.
--- End quote ---
Yes, I tried capping every single vacuum port off... no change in the issue. I have also put on new intake manifold gaskets recently in an effort to solve the issue. No change.
NathansCorvette:
--- Quote from: Kenth on November 21, 2024, 01:20:24 PM ---The original ignition coil has 1.8-2.0 Ohm primary resistance and about 1.3 Ohm added from the resitor wire with engine running.
MSD Blaster 2 coil has 0.7 Ohm primary windings and is aimed for electronic ignition systems. Running this coil with points requires a special resistor to get 3.1-3.5 ohms with engine running or the points will burn out and degrade performance.
Using the correct ignition coil could be a good start when troubleshooting.
--- End quote ---
Again, there was no difference at all when changing from the delco coil to this new one, not in the engine performance or in the issue. Perhaps its some other problem in its own, not that I've noticed anything, but I'm confident it is not what's causing a momentary rich condition when the accelerator pump is actuated with a hot engine... But I will look into the resistance to make sure I'm not frying my points.
NathansCorvette:
--- Quote from: quadrajam on November 21, 2024, 04:14:13 PM ---....???..Tough one. Usually the other way around. How bout metering rods too short or hanging
too high.... PP spring way too strong.... No vacuum under power piston...
Reach in through the vent tube with a tiny screwdriver and check that you can push on
the hanger and move the PP up and down. Then check to see that its down at idle.
QJ
--- End quote ---
It is the other way around! In my searching, I've found a thousand closed cases of an off-idle bog solved by a new accelerator pump... I can't find ANYTHING about my issue online.
Now you're talking more about the things I'm starting to suspect. I will try moving the power piston like you say.
I don't know anything about metering rod sizes so I'm unsure what type I have.
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