I had a weird thing occurring with fuel pressure last year that I thought I solved. I race racepak iq3 dash and sportsman. As I go down the strip I will get occasionally the fuel pressure light flickering as a warning. There car performs within .00x thru intervals. Does it also then doing burnout.

Pump is magna 500 pro, -12 to pump, changed filter, -10 to front, sensor is just past regulator in front -8 feed line.

Let year I changed the sensor and it went away. This year the only winter change was I flipped around carb to get throttle enhancer and Morse cable on. So now rear feed is front feed.

The lights only flicker occasionally. Could I be getting air in the tank and pump is loosing pressure for instance from air bubbles? I don't have any foam in tank (took it out when I went to alky). Should I put it back in? Advise on where to buy alky compatible foam.

How much effect does the little pressure flickering have on the carb? I used to be fuel injection guy, and don't know as much about pressure on carb. My mind is thinking the Bowls are at atmosphere pressure so as long as they don't get low to starving the motor it shouldn't matter.

I'll try to pull the data down. I have a wide band as well.

Any ideas

Electric pump with alky? Where is fuel cell at? How is pump mounted? What is the line pressure to the regulator? At the carb?

Yes electric pump. Magna fuel 500. Mounted under the car below cell. Regulator near carb up front. Cell in rear of the car. -10ptfe line to front.

What's the line pressure to the regulator?

Believe 28 set from factory. Never touched it.

Main question is what effect does it have on carb if it would truly be doing to 8 from 9psi for split second. The light just flickers. I'm wondering if it's vibration making the racepack sensor go wacky

quote:

Originally posted by ski_dwn_it:
Believe 28 set from factory. Never touched it.

Main question is what effect does it have on carb if it would truly be doing to 8 from 9psi for split second. The light just flickers. I'm wondering if it's vibration making the racepack sensor go wacky

Do you have a mechanical gauge to put on and try? Maybe try to get a good mechanical gauge and put a GoPro on it or something..

Is your setup a bypass regulator?
If it is a deadhead setup, I could see a "burp" of air being trapped in the line, but probably not with a bypass regulator. If it is a bypass setup, your return line should be at least as big, (or larger), than your feed line.
Does your O2 graph show any lean spikes during run?
If you are not seeing any change on the timeslip, my guess is nothing to worry about, and dropping to 8 PSI won't hurt a thing. I used to run 9 PSI when I switched to alky, would occasionally have issues with overly rich condition, (pressure over powering the needle & seats). After reading much advice on here, I have dropped my pressure over the past couple years, it seemed to run much more cleanly at 7-7.5 PSI. Have gone as low as 6 PSI with no issues.
I suspect you are right, if not air in line, could be vibration, or maybe intermittent problem with sensor. I like the idea put forth by NC3x58.

Couple of thoughts.

Does the bypass line just dump fuel in the tank on top? No line in the tank to discharge the fuel below the fuel level? If this is the case and especially if its near/over the supply to the pump fitting, it can cause issues.

The next thing is simple, the closer you get the sensor to the carb the more funny stuff you will see. Pressure will vary a bunch because of the needle and seats opening and closing during a run. Why not put the sensor in the regulator on the low pressure side?

That might be what I am seeing. I used to have a mechanical gage on the windshield that was fed with a -6 or -8 line. When I got the sensor for racepak the guy told me I could just put it at the end of that line which is Teed off the front bowl feed. In essence it is likely 5-6 feet away from the regulator.

My regulator was from pro-system and it did not have a port for the pressure. Hence the Teed off lines I have.

And yes fuel comes back into tank from above. But opposite end of the sump. Drops in at front and pickups at the rear. 8 gallon tank I keep ~6 gallons in.

What is the alarm? I had a similar issue. My low alarm was set to -1 and when I shut the car off I would get this alarm. So I just changed it to -2. Problem solved. Do you know the alarm limits?