Fuel pressure climbs at idle

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19blockhead72

19blockhead72

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I have a 74 Sport with a mild 408 with a Edelbrock 750 carb. I just installed an electric fuel pump, my first one. I have a Holley blue pump and a Holley regulator. I hooked it up "dead head" no return line. I fired it up and everything works well. I set my pressure right at 6psi. The only problem that Im having is that if it idles for a bit the pressure climbs a little bit. It will go to 10 psi but as soon as you open the throttle it drops right back to 6 psi. Any ideas? Should I even worry about it?
 
If it ain't pushing the needles off the seats and causing flooding I would not worry. At WOT will it hold 6 PSI?
 
Crank the idle-speed up,lol.
Kidding
They call that regulator creep.
Some carbs put up with it. It's like Gerald said.
But make sure your EFI rubber jumpers are solidly connected and cannot blow off. Try to imagine how dangerous even a few seconds of that Holley running WFO would be! I doubt you would catch it before your car erupts in flames.
Personally, I proba, no make that I would install a return line. And I would try to run the regulator after the carb, if that is possible..
 
A return line is something I may do. Just wanted to start with a simple system to start. I used Summits fuel injection clamps and I have the regulator attached directly to my hard line to the carb. Should I turn the pressure down a little for now? Like I said my carb seems to be fine with the pressure.
 
For around town sure; you hardly need any pressure around town, but you do need volume.That's the nice thing about the mechanical pump; Low delivery at idle and volume rising with rpm. And the HO pump only puts out about 8psi dead-headed.
 
AJ/FormS said:
For around town sure; you hardly need any pressure around town, but you do need volume.That's the nice thing about the mechanical pump; Low delivery at idle and volume rising with rpm. And the HO pump only puts out about 8psi dead-headed.
Click to expand...
I had a nice Edlebrock 110gph mechanical pump, loved it but when it was hot and I would go to wot it would sometimes fall on its face. The reason for going electric.
 
I use the P4007040; rated 80gpg@8.7. It's been on my 367 since 1999 with a 3/8 all steel supply line .Street only, and running a minimum engine temp of 205*F. She goes 93mph in the 1/8th, without issue. Sorry to hear yours couldn't keep up.
 
Run a return line. It's no fun sitting on the side of the road cuz your fuel is hot....
 
AJ/FormS said:
Crank the idle-speed up,lol.
Kidding
They call that regulator creep.
Some carbs put up with it. It's like Gerald said.
But make sure your EFI rubber jumpers are solidly connected and cannot blow off. Try to imagine how dangerous even a few seconds of that Holley running WFO would be! I doubt you would catch it before your car erupts in flames.
Personally, I proba, no make that I would install a return line. And I would try to run the regulator after the carb, if that is possible..
Click to expand...

My next suggestion was if it drops to 4 PSI or less then run a return and crank up the regulator!
 
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