Question on loosing fuel pressure going down track.

[Jeff Stout]

Originally Posted by ss3011

Its weird that the O2 sensor goes rich , sounds like some work needs to be done to straighten out the fueling of the carb . That being said the carb is using more fuel than can be supplied to it , so the pressure drops . My recommendation is to figure out what's up with the carburetor , but also make sure your fuel system is up to the task . My Q-jet is fed from a BG400 pump through a dash 10 line , and stays right at 6.5 psi throughout the run . Dyno pulls show the A/F ratio varies from 12.8 at 5000rpm to 12.4 at 7400 rpm .

This seems to be what I'm struggling with. I make small changes to jet,rod,hanger and have not found sweet spot. In the beginning I was way over rich and way over revving on gear change and car went faster. Would think car would pick up allot if afr was correct in 3rd gear

[Dave Gantz]

Did you do the volume test with the engine running? It'll pump more, of course, when the voltage regulator is holding it at 14.7v or whatever it maxes out at.
As mentioned, are your grounds, connections and wire diameter up to snuff?

[Alan Nyhus]

Originally Posted by Jeff Stout

I just did now im right at a gallon in 60 seconds. That was tested using line right at carburetor

Jeff, you don't have foam in the fuel cell do you? Bob Sherwood mentioned the foam yesterday when we were talking about this thread.

Assuming no foam in the tank, start working it back. Take the filter element out and recheck it at the carb. If no change, check it before the regulator. If that's still the same, check it right out of the pump. Make sure the fuel cell vent is open.

Let us know what you find. -Al

[Crisco]

How old are your fuel lines?

[Mike Pearson]

Originally Posted by Jeff Stout

I just did now im right at a gallon in 60 seconds. That was tested using line right at carburetor

Like other have said a gallon in 60 seconds is not enough volume. At your ET you would be getting less than 1 Qt. of fuel to the carb during your runs. a gallon in 30 seconds is right on the edge for my car.

[Jeff Stout]

No foam in cell. I'm going to bypass filter and retest filling time in bucket. I did notice once after shutting off car the cell acted like it was under a vacuum when I tried taking cap off. I will look at vented line to see if it collapsing or kinked. All lines,fittings,filter,pump,cell were all brand new.

[Tom Broome]

Originally Posted by Jeff Stout

No foam in cell. I'm going to bypass filter and retest filling time in bucket. I did notice once after shutting off car the cell acted like it was under a vacuum when I tried taking cap off. I will look at vented line to see if it collapsing or kinked. All lines,fittings,filter,pump,cell were all brand new.

Here in the Southeast. it's not unexpected to find mud-dauber plugs in things like a fuel cell vent.