Question on loosing fuel pressure going down track.

[Jim Wahl]

Originally Posted by Kenny Wigington

You may be having a voltage drop issue. The bigger the feed wire, the better, and closer to the battery, The better you will be. Double check your ground connections, to the pump and relay, too. 10 gauge to pump, at minimum, and 8 would be even better.
If you have a good meter, try to read the voltage, thru the relay, it might show you a problem there.

Either this or your old pump is just worn out! Jim


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[Chevy55]

From Areomotive

At the track, from the launch to mid-track, fuel pressure is steady, but then down track, it falls 2 PSI or more, what’s wrong?

The first thing to be blamed is usually the regulator, but in fact this is a strong indication of a fuel supply problem. If for some reason there is insufficient volume available from the fuel pump to feed the engine, fuel line pressure can drop to the carburetor. Even with a static regulator, a significant drop in line pressure affects flow through the regulator, causing regulator pressure to drop. Do not automatically assume the pump is bad or inadequate, inspect and resolve any supply line issues to the pump, ensure the tank is vented and the vent is functioning, and be sure to check the fuel pump wiring, along with the overall electrical system performance. Finally, if you still have problems, contact Aeromotive for a proper flow test you can perform in the field to verify if your fuel pump is performing properly.

[jim morgan]

Or maybe you don’t have a problem, Before all this high pressure,high volume systems
I had a max wedge , Carter electric and manual pump had 6 pounds thru the lights at 2 pounds went 127.5 mph that’s 30 years ago, is your car nosing over, ?

[Jeff Stout]

Originally Posted by jim morgan

Or maybe you don’t have a problem, Before all this high pressure,high volume systems
I had a max wedge , Carter electric and manual pump had 6 pounds thru the lights at 2 pounds went 127.5 mph that’s 30 years ago, is your car nosing over, ?

With it being a fairly new combo to me. My opinion is that it is not nosing over as the mph matches the et. Side note is the o2is going from 13.5 to 11 in high gear.

[Greg Hill]

What brand of pump do you have? A q-jet is notorious for being hard to keep supplied with fuel. When I built my car it had a 780 Holley and I was using a Mallory 140 pump and a 3/8 fuel line from the tank to the regulator and everything worked great. When I switched to a q-jet combination I ended up switching to a Barry Grant 280 pump and a 1/2 inch line from the tank to the regulator to get it to run right. The amount of fuel to a q-jet is critical.

[Alan Nyhus]

Take the line off at the carb, run the fuel pump for a full minute and measure the volume it pumps. Do this with the gas cap on and off to see if there's a difference. -Al

[Nick_Siebert]

I had the exact same problem become present on my 305, Q Jet Camaro, it was a faulty pressure regulator at the carburetor.

[Ed Wright]

Is this a stock fuel tank? Not a fuel Cel?
To eliminate a weak (low volume) pump, I would add 5 gallons of fuel. If that stops the pressure drop, it will usually indicate the pump pick up being uncovered due to placement in the tank.

[Dave Noll]

Originally Posted by Jeff Stout

Side note is the o2 is going from 13.5 to 11 in high gear.

Trust the sensor, there isn't a problem. Its 11:1 in high gear. My cars AFR gets leaner as RPM increases an gets richer at each shift. (completely different carb)