Not sure if this is my issue yet,,,but,,,need to know how to "adjust" the bypass on my fuel pump.



10 sec, bracket car,,,fuel pressure bouncing around,,I replaced the pump ( was a old, small, holley black pump ).......put on a Mallory 250.....AND a "small" inline summit 40 micon filter before the pump.



Fuel pressure seems fine for a bit at idle,,,,,but when i launch,,,,it drops to 3-4 all the way down the track,,,and would not come back up on the return road,,,or in the pits.....



Pulled the small, inline, 40 micron filter off,,,and it looked a bit "gummed" up....cleaned it out,,,,fired it back up,,,and fuel pressure now normal,,,,,,, drive around,,,race,,,,and pressure drops again....



SO,,,,,,,,, i am thinking i have too restrictive of a fuel filter before the pump ?



I replaced the "small" filter with a Aeromotive 100 micron filter,,,,and so far,,,at idle,,,in the garage/driveway,,,,the fuel pressure reads normal,,,,,,BUT,,,,,have not had a chance to run the car yet......



Hoping to get to the track today,,,,,,my concern is what to do if the fuel pressure drops again down track,,,,,,( which should rule out a filter problem)



I am wondering if the next thing to consider could be the bypass on the fuel pump ??



Not sure how to "adjust" the bypass,,, ( i know "how" to and where the adjustment is ),,,,but which way to turn the adjustment screw ? in ? out ? how much ? I dont have a gauge after the pump,,,and before the regulator as of yet,,,,,



just want to know what i can try if i get to the track,,,and the fuel system starts acting up,,,,



ps,,,this is a dead head system ( for now )



sorry for the dumb questions,,,,,,,,,,thanks for any help.


This is my last ET,,,,running down track with 3-4 lbs of fuel pressure,,,,hoping to get out this weekend and take a shot at a NINE...........

Doug - do you have the bypass line hooked up on the pump and routed back to the fuel cell??? - I am guessing that pre-filter has been your issue - I normally run 2 lines into the pump. Adjusting the bypass pressure requires a second fuel gauge after the pump and before the regulator - I have never had to adjust the pump bypass with the mallory - I think they are pre-set at either 16 or 20lbs

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do you have the bypass line hooked up on the pump and routed back to the fuel cell???

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Yes

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am guessing that pre-filter has been your issue

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I think so,,,,i took the car out today,,,,1st time with the bigger 100 micron pre filter,,,and the pressure seemed to be stable all the way down the track,,,i hope this fixed the problem i was having with the fuel pressure bouncing around and nose diving down track,,,,

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Adjusting the bypass pressure requires a second fuel gauge after the pump and before the regulator - I have never had to adjust the pump bypass with the mallory - I think they are pre-set at either 16 or 20lbs

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I thought i had read somewhere it was around 15 ?-16..
I dont have a gauge after the pump

Do you think it would be wise to "eventually" plumb in a return style system,,instead of the dead head ?