Fuel Pressure setting

[Steve Walters]

  This might seem stupid butt has anybody else had this problem?
I set my fuel pressure regulator on 7 PSI with the fuel pump on and the engine not running, it stays there until I start my engine, then it starts to climb up to 17 PSI at idle.  If I try to turn the regulator down at idle it stays at 17 PSI, until I shut every thing down, then when I turn the fuel pump back on it is to low.  Its a magnflow 500 pump, 10 an to regulator, two 8 an's from regulator to Holly 850 DP, the pressure gauge is on the regulator.  The bypass is off of the pump to the fuel cell.

Steve

   

[hotrod]

Check your voltages at the pump terminals under both conditions.
If you have an alternator, you might be delivering considerably more voltage to the pump with the engine running than with the engine off.
Also check for a high resistance hot lead or ground on the wiring to the pump. It might not carry much current engine off, but with full system voltage (assuming alternator puts out 13.8+ volts) you might over power the high resistance and deliver adequate voltage to the pump engine running.

Electric fuel pump fuel flow rate, can be significantly affected by supply voltage variation.

Larry

[thundersalt]

We had the same problem with our magna fuel pump. We set it with the engine running. We also have a gauge on the hi pressure side and found out that the bypass is not pre set to 26 psi(?) like the factory tag says. Since we started adjusting with the engine running, the problem has mostly gone away. We check it before every pass and noticed it changes a little with altitude changes during the day at Bonneville.

[Steve Walters]

I do not run an alternator two optima red tops one for pumps, one for ignition and gauges.  I will put a pressure gauge on the pump side of the regulator, and see what it is doing.  It doesn't come off of seventeen with the regulator cranked all the way down, maybe I will have to get two regulators.  Thanks for info.

Steve

[manta22]

Steve;

Make sure your bypass return line can handle the flow-- bigger is better.

Regards, Neil  Tucson, AZ

[Steve Walters]

Gary W called me on the phone and gave me a lesson on regulators, new ones verses old ones, and in the process I rembered that when I flushed my lines, I flushed them through the regulator.  Next morning I back flushed the lines with the feed side of the regulator off, end of problem.  Thanks for the help.

Steve 

[jimmy six]

Steve I don't know your program but I would suggest an alternator. I ran 25 years without one and 15 with one and I'll never go back to not having one unless I can't phsically mount one.

IMO No matter what your ignition is (other than a magneto) 14 volts is better than 12+ anytime. You will make more power than the little hp the alt takes. Electronic ignitions like alternators...Good Luck

[Cajun Kid]

Steve I don't know your program but I would suggest an alternator. I ran 25 years without one and 15 with one and I'll never go back to not having one unless I can't phsically mount one.

IMO No matter what your ignition is (other than a magneto) 14 volts is better than 12+ anytime. You will make more power than the little hp the alt takes. Electronic ignitions like alternators...Good Luck

I AGREE  (make sure you have a good ground too)