Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

'78 Suburban 'chugging' on long grades

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RyanAK:
As way of an update...truck is running well down the highway. No fuel starvation issues. Can't believe it was a bonked out new fuel pump!

New issue though... when the truck is at operating temp and idling - whether in Park or in gear - the engine will occasionally stumble hard and then recover. Idle in P is ~900RPM and it'll stumble down to under 500 and then come back. In gear were around 700 and it'll stumble to almost stalling out before smoothing back out.

I popped the air cleaner so I could watch. I can see the fuel level increase in the bowl by looking down the secondary rods. Up it comes...stumble... down it goes... smooths back out. Does it just once occasionally, or it'll start cycling like this every 20 seconds.

I have a video but can't seem to post.

Float is set at 15/32. New pump is pushing ~8psi. Non-check-valve filter. Zero issues while driving.

Thoughts?

RyanAK:
Video!

https://youtu.be/Iz53f_OCZ6g

Cliff Ruggles:
Flooding.

Haven't ran into one doing what yours is but for some reason it's having fuel control issues. 

It will be float, N/S, fuel pump/pressure related....

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