View Full Version : Pressure fluctuates what to do?

ss dave
01-12-2009, 10:08 PM
Recently changed in-tank pumps due to my Aeromotive A1000 starving the pick-up at low volumes. Went with a Bosch pump.
I have 44.5 # injectors, Fast rails and run 58psi.
Now with new pump at 3/4 throttle, accelerating I get a brief pressure drop from 58psi to 52psi. The motor doesn't nose over, I can't tell that it affects it at all. It is a parallel set-up with the regulator behind the injectors.
Should I be concerned? Is this a tuning fix?
My Aeromotive stayed rock solid at 58psi, but it moved alot of fuel.

01-13-2009, 09:12 AM
If the pressure drops, the car goes lean unless it was [not the right way to do it] tuned around the pressure drop from the beginning. If it was tuned at a stable 58psi though and it falls now, then the car is leaning out. The PCM cannot see fuel pressure and at heavy to WOT cannot make correction.

Lonnies Performance
01-13-2009, 08:41 PM
Not sure of your exact configuration....

Are you running aftermarket lines?
What brand of regulator?
Is a vac line attached to the regulator & where it is connected?

How long does the the pressure remain low?

Give me some more info & I'll try to help.

ss dave
01-14-2009, 09:47 AM
Great, have a modified Ricks mini tub tank which we added extra baffle doors to help with slosh. Recently switched pumps as stated above.

It is a custom parrallel feed/return line set-up. Y block split into two lines that feed the FAST High Flow rails with a Weldon regulator on the return side, I don't think it has a vaccum line- I'll look tonight. Bosch 44.5# injectors.

With the Aeromotive pump I never had fluctuations upon acceleration, but with low fuel volumes in tank and when cornering (slosh) it would starve the pick-up. At fuller tank volumes- no problems. Rock steady pressures. Switched pumps thinking that the Aeromotive was moving alot of fuel so fast that at low volumes it would starve at the pick-up.

Switched pumps and now on 3/4 throttle acceleration I'll get a brief, maybe 1-2 maybe 3second drop in pressure from 58psi to 53 or 52psi, then it recovers.
Thanks for any input.

01-14-2009, 12:30 PM
What type of fuel pressure gauge are you using? Is it dampened and/or liquid filled?

ss dave
01-14-2009, 02:19 PM
I have two, one on the regulator and an Auto Gauge Comp II inside.

Lonnies Performance
01-14-2009, 05:47 PM
Is this in the stock bucket?

Is the sock in the bucket or outside?
Is the venturi functioning?

Feel free to call me to discuss.
724-322-8505 until 11:00pm eastern time

ss dave
01-14-2009, 07:06 PM
Thanks Lonnie, No sock. Pick -up tube into 10 micron filter. No bucket, just baffling around pick-up tube. Custom Ricks tank into my 69 Camaro with an LS7


01-15-2009, 11:03 AM

o god, I just got wood :D

01-15-2009, 11:20 AM
WOW, just WOW. That's awesome.

ss dave
01-15-2009, 03:58 PM
Thanks, now if I can fine tune this psi stuff, I'll sleep better

01-15-2009, 04:11 PM
guh, goo


Lonnies Performance
01-15-2009, 07:46 PM
Nice ride!!!!

But based on the info I can not determine your configuration.
Give me a call sometime.

ss dave
01-15-2009, 11:35 PM
Thanks Lonnie. I'll have my FI guru call ya.
Gauges at idle.