Possible Fuel Pump Pressure Issue

afeustel

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Decided to replace my electric fuel pump due to uncertainty of the type and the fact that the fuel lines were somewhat pinched from the fuel line routing. Also wanted to be sure I was feeding the dual Weber 36 carbs with the correct pressure.

So I came across the info on this website:
http://www.racetep.com/webfuelspark.html#webfuel

and went ahead and purchased and installed a Carter 4070 pump as suggested.

Now it seems that the carb is running very rich at idle since I now have to turn in idle mixture screws (lean it out) to bring up the rpm and open the butterfly's by a few turns just to keep it running.

So my question is whether anybody else has tried this pump and if so, have folks always used a pressure regulator to bring the pressure back down. The pump is rated at 4-6 psi (guessing I am seeing the higher end at 6). Have not actually put a pressure guage on the line yet but the before/after symptoms point to too much fuel.

Is there another in-line pump that offers a better alternative?

Thanks
Drew
 

jmackro

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A lot of what is said on the website that you referenced does make sense - a Weber carb should receive fuel at relative low pressure - say around 4 psi. If your pump is putting out 6 psi that is too high.

But I am puzzled why the author of that web write-up keeps refering to how much volume Weber carbs need. Whether you have a Zenith, Weber, or Holly carb on your engine, it would need the same amount of gasoline to maintain its proper fuel-air ratio. I can't figure out why Webers would need a pump capable of putting out 60-70 gallons/hr?

I am also puzzled why the guy is so negative on regulators. Contrary to what he writes, fuel regulators are not simple restrictors. And heck, the float + needle valve in every carburetor is a regulator of a sort.

I would begin by measuring the fuel pressure at the carb. If it is > 4 psi, then an adjustable regulator would allow you to dial in the correct pressure.
 
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Stevehose

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I have a Holley 12-804 regulator hidden in the spare wheel well. I set it at 3.5 lbs for my 3 webers and have not had any fuel volume issues. Make sure you use thread sealer on all fuel fititngs for this and the pump.

https://www.holley.com/12-804.asp

And I also put a dab of epoxy on the Carter's wire connections to keep them from falling off.
 
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afeustel

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Still Running Rich at Idle

Installed the 12-804 which is claimed to be factory set at 2.7 psi. However the car still seems to be running very rich at idle and the butterfly's have to be opened a few turns just to keep it going.

I know...need to put a pressure guage to see what it is really providing for pressure but it seems odd to me that the new pump and regulator are still so far off that the car is running super rich. Nothing else was changed in this transition.

On Weber 38's, is it possible to set the floats so that they are simply not closing off fuel flow now (due to previously low fuel pressure)?
 

afeustel

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Fuel Shut-off solenoids

Tested Fuel pressure is stable at 2.7 lbs.

I have fuel shut off solenoids installed. It won't run properly (symptoms posted above) unless I take them out and put the brass plugs back in. However, the solenoids bench-test as if they are working as intended (i.e., they retract when powered).

Any thoughts and have others had problems with shut off solenoids even if they appear to work fine on the bench?
 

Stevehose

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Are you testing these on or off the car? If on the car do they activate when turning the key? If not are they getting 12 volts from the ignition?
 

afeustel

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Tested on and off the car.

Tried to just tinker with one at a time. Have the car properly tuned and idling just fine without the solenoids installed. Then I installed the front solenoid and restart the car. Idle is poor and low. Then hook up 12V directly from battery to solenoid and no change. Always blip the throttle inbetween to reset the idle but still no joy with the solenoid installed. Then swap the solenoid back out and restart and car runs fine.

On the bench, solenoids appear to function normally when power applied.

Does not make sense that they dont work when installed. Checked that carb provides a proper ground for solenoids as well. These are new units, I actually have 4 of them.

Am I supposed to change the size of the small brass jet-like object that fits in the end to accomodate the solenoid plunger?

Any thoughts or assistance appreciated.

Seems the problems in the original post were actually caused by the solenoids and not the fuel pump (forgot to mention that I had also made that change at the same time as the install). Should have stuck to the theory of not changing more than one part at a time.
 
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