Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem
Q-jet flooding under load
rwberinger4x4:
Hi all,
I have something of a frankenstein set-up, so bear with me!
1965-66ish Small Block Chevy 283
350 Edelbrock SP2P intake
1967 Buick A/T Quadrajet S/N: 7027244
I believe it has an RV cam but I have never confirmed
All of this is loaded into a 1975 Toyota Land Cruiser with the rest of the drivetrain remaining stock Toyota
I rebuilt this carb with Cliff's SR Kit 3 years ago. At that time I also tapped, capped, and epoxied all the well plugs. Throttle plates didn't show significant play.
After the rebuild, and for the past 3 years, the carb has run pretty well. Always a BIT rich, but I equated this to overjetted/oversized for the engine.
I just installed a new Carter 5.5-6.5psi fuel pump (30gph), and hard fuel lines to the carb this week, and all hell broke loose!
At idle: Truck idles fine, it's very responsive to idle screw and mixture screw adjustments
When "revved" standing still - Throttle response is good. Small amount of black smoke from tailpipe (rich)
When held at about 2000RPM for about 10-15 seconds, the truck tries to stall when I come OFF the throttle.
When DRIVING: The truck gets about 100 yards in 2nd gear, then the carburetor completely floods out, truck stalls - gas out the accelerator pump shaft, the baseplate gaskets, backed up into the venturis, and all over the manifold.
What is going on here? Normally this points to a float or needle and seat problem, right? I suppose it's possible that some "crud" in the fuel lines made it through an inline filter AND the carb inlet filter and plugged them, but it seems unlikely.
Wouldn't a clogged needle/seat to a sinking float cause problems all the time (idle, revving, moving, etc.)
Any input would be greatly appreciated!
rwberinger4x4:
In addition, for what it's worth - I strongly suspect the stumble/stall coming off a rev is possibly the carb trying to flood.
I haven't checked the pressure coming off the new fuel pump yet to confirm it's really 5.5-6.5psi.
Cliff Ruggles:
If all the problems started with the pump install, that's the first thing to check....Cliff
rwberinger4x4:
Well, I went to check the fuel pressure tonight, and the barbed T-fitting for my gauge cracked - I have another one on order, I'll get back to you soon. Thanks for responding!
rwberinger4x4:
Hi Cliff -
Checked my fuel pressure tonight. Connected the gauge with a brass T-fitting. The results were...odd..to say the least.
The first time I started the truck (cold start) the fuel pressure was jumping around 6-9 PSI (too high, it should be a 5.5-6.5PSI pump).
here is a video:
https://youtu.be/oG6-fj_bp-4
I shut the truck down before it even got fully up to operating temperature - (the engine then flooded on shutdown)
When I started it back up about an hour later, the gauge went completely haywire. Became unreadable when you revved the engine:
https://youtu.be/uJ2rDaBIudE
And lastly, here is a (not great) video of the carb primaries - does this seem like excessive fuel to you?
https://youtu.be/5ca80rJhhKk
After the engine is shut down, the gauge sits at about 7 PSI.
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