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-   -   Question on loosing fuel pressure going down track. (https://classracer.com/classforum/showthread.php?t=75236)

Alan Nyhus 01-23-2020 08:45 AM
Re: Question on loosing fuel pressure going down track.
 
Quote:
Originally Posted by Jeff Stout (Post 606668)
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 01-23-2020 09:07 AM
Re: Question on loosing fuel pressure going down track.
 
How old are your fuel lines?

Mike Pearson 01-23-2020 09:31 AM
Re: Question on loosing fuel pressure going down track.
 
Quote:
Originally Posted by Jeff Stout (Post 606668)
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 01-23-2020 10:35 AM
Re: Question on loosing fuel pressure going down track.
 
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.

Jeff Stout 01-23-2020 10:42 AM
Re: Question on loosing fuel pressure going down track.
 
Quote:
Originally Posted by ss3011 (Post 606675)
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 01-23-2020 12:18 PM
Re: Question on loosing fuel pressure going down track.
 
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?

Jeff Stout 01-23-2020 12:40 PM
Re: Question on loosing fuel pressure going down track.
 
Quote:
Originally Posted by Dave Gantz (Post 606711)
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?
Going to verify ground as car was a back east car and frame had some rust. Maybe move ground to rear battery.

ss3011 01-23-2020 01:45 PM
Re: Question on loosing fuel pressure going down track.
 
Everyone is focusing on a fuel pump delivery problem , yet the engine goes rich in high gear . That seems to be the real problem .

Bob Mulry 01-23-2020 02:30 PM
Re: Question on loosing fuel pressure going down track.
 
Quote:
Originally Posted by ss3011 (Post 606719)
Everyone is focusing on a fuel pump delivery problem , yet the engine goes rich in high gear . That seems to be the real problem .
Just my 2 cents.....

A lean miss will do that....

ss3011 01-23-2020 05:52 PM
Re: Question on loosing fuel pressure going down track.
 
Quote:
Originally Posted by Bob Mulry (Post 606721)
Just my 2 cents.....

A lean miss will do that....
Doesn't a miss make an o2 sensor read lean ?


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