fuel pump pressure ?

[eclipsegse]

i am running a ump modified with a mechanical fuel pump on alchol how pressure shoud i run

[dirttrackrocker]

Around 3 at idle and 9 at WOT

[eclipsegse]

it stays at a constant pressure doesnt go up or down once i set it thats what it is ive been setting it at 6.5 psi is that enough it doesnt go down when on throttle im using a barry grant mechanical fuel pump

[dirtrace09]

What type of bypass are you running? I am guessing you are running a regulator which doesn't work for what you are trying to do.

[dirttrackrocker]

You have to have a bypass regulator that has a return that goes back to the tank.

[eclipsegse]

using a barry grant regulator that has a bypass and it returns to tank

[dirttrackrocker]

Is it the one that has the Jet inside to reduce idle pressure? I think the red ones don't have a jet and the black ones do. Where do you have it in your fuel system? It should be on the back of your fuel log AFTER the carb.

[Dirtrunner35]

I wish I could answer the question he asked but I want to know also. How much fuel pressure should you run on alcohol in a modified.?????????????????

[eclipsegse]

no jet and it is on back side of fuel logand the fuel gauge line is hooked to the center of fuel log it comes from tank to pump to fuel log then regulator is on back of log and the return comes out of regulator and goes to tank

[dirttrackrocker]

Hmm.. The only thing different on mine and all the others I've seen is the line for the gauge comes out the back of the regulator. Not sure it makes a difference as long as the return is coming out of the bottom.

[SnapOn35]

Same as above 3 at idle and 9 at wot for alky with the regulator on the back of the log and guage line coming out of middle of log is how we run ours also with no problems

[eclipsegse]

ok i guess im not making this clear i am using a mechanical pump ran of of the cam like a stock motor my pressure does not go up and down once i set it it stays there so where should i set it ?????

[washeduptoo]

I'm not an engine person but to me you have to set it to relieve at 9 at wot. Hopefully someone can be more precise and good luck.

[js11]

BG bypass system goes to the front of the fuel log. To get 3 to 4 lbs of pressure at idle, make sure the adjustment screw on the bypass is at the 4 to 5 o-clock position. you need 9 to 15 lbs of pressure when wide open.

Good luck

[dirtrace09]

He is running a regulator with a return. The problem is that you should run a bypass system either by BG or C&S when using a stock style pump. I am also assuming that you have a 15 pound pump on the motor.
Your pressure is set at 3 pounds at idle just like stated above. You want to hit atleast 9 at full throttle. The idea of a bypass system is it uses a butterfly or cup with a hole in it to rotate open (to relieve pressure at idle) or closed (full pressure at mid to high rpms). I have never seen anyone have any luck with a regulator and alcohol. Everyone I know is on a mechanical bypass system when running a stock style diaphragm pump.

[dirttrackrocker]

You are running the exact system I am running. Mechanical pump, Bypass regulator on the back of the fuel log. It should go up and down when you rev the motor, it needs to be 3 at idle 9 at WOT. Are you sure you have the return coming out the bottom of the bypass regulator and not the back? I know LOTS of people running this set up, so don't let anyone tell you it won't work.

[eclipsegse]

the regulator is shaped like a tee one end is on fuel log and other end is plugged off and the center is the return pressure bouces around 3 to 7 at idle and stays at 7.5 when u are on gas it runs fine was just wondering if the pressure was ok

[dirttrackrocker]

Yeah, it will bounce at idle, I would try to get it up closer to 9 at WOT if you can.

[Kojak_9x]

I have always ran 4 psi at idle and 12 at wot. ( BG bypass that bolts on under the carb. Thats with my motor and where I race so it may differ on engine ect.... I want to say I read on BG's website with alky you want 3-5 at idle and 11-13 wot.. Good Luck!!

[tia12]

alcohol is higly volatile. keep it low.