Fuel Press. Regulator Location for Carbs

[pSquared]

Wondering where to locate the fuel pressure regulator for dual carb set up.

Seems to me, could make a difference if it's ahead of, or down stream from the 'T' where the line returns to the tank.

See attached. Thanks for any thoughts.

p2

[John Rogers]

With my race car we never used a return line, it was blocked off at the tank. The pump will be a low pressure type, not the fuel injection one and they generally only put out 5 or 6 pounds. We mounted my regulator on the read engine compartment wall and then a tee fitting to the carbs and also mounted a small racing fuel pressure gauge so the pressure could be checked when starting the engine. Normally you'll want 3.5# to 4# of pressure for Webers will be plenty.

[pSquared]

Forgot to mention---using the stock FI fuel pump, by the way, which is why the Pressure Regulator
to step it down.

Thanks,

p2

[John Rogers]

The stock FI pump will not work, even with a pressure regulator. If you search you will find posts here and the other two 914 websites that talk about this and the ability of a regulator to drop fuel pressure from about 30# to 4# is nearly impossible to do and have it work well.

But go ahead and try it since it sounds like you are set on doing it so please let us know if you ever get it to work.

[snbush67]

The fuel pressure regulator should be set up similar to the first diagram. The regulator has an inlet where the high pressure fuel enters, the an outlet where high pressure fuel returns, and a second adjustable outlet to the carbs. The controlled outlet is what is bled out from the high pressure stream flowing through the block.

You shouldn't have any problems regulating a constant pressure as long as the rest of the fuel system is in order, no leaks or blockages.

[Dave at Pelican Parts]

It is a bad idea to try to choke the stock FI pump down to a carb-friendly pressure and volume. All it takes is one kink in a line and you have fuel being dumped into the carb throats. You also wind up with very fiddly little adjustments to the FI pressure regulator having large effects on delivery. And most carb pressure regulators can't cope with the high pressure and volume that the FI pump delivers.

It is far better to get a pump that actually delivers something close to the pressure and volume you need.

That said, the second setup in your diagram won't work at all, for any part of the fuel circuit.

--DD

[porschetub]

Originally Posted by Dave at Pelican Parts

It is a bad idea to try to choke the stock FI pump down to a carb-friendly pressure and volume. All it takes is one kink in a line and you have fuel being dumped into the carb throats. You also wind up with very fiddly little adjustments to the FI pressure regulator having large effects on delivery. And most carb pressure regulators can't cope with the high pressure and volume that the FI pump delivers.

It is far better to get a pump that actually delivers something close to the pressure and volume you need.

That said, the second setup in your diagram won't work at all, for any part of the fuel circuit.

--DD

Dave would I be correct it saying the F.I. pump with just overwork and die a rapid death ? .
I run a electronic copy of the old British type electric pump,designed to run 2-6 pound( from memory),nice wee unit with a holley fuel pressure regulator, cost all up was around $150 ,fuel pressure is consistant on my gauge.
And yes the pressure is critical,if I adjust the pressure above 3.8-4 pounds with my Webers the engine races ,floods and stops very quickly.
The needles and seats can't hold the pressure and the raw fuel spills over to the throats.
I would say a low pressure regulator wouldn't work with a high pressure pump for starters,not what they are designed for

[pSquared]

Curious, but not surprising. Ran it w/orig. fuel pump and reg for a number of years & seemed to do o.k. Been off the road good long while, but may be excess fuel pressure one of the reasons why died on me back when.

None the less, very informative and helpful info. Gonna dig out the fuel pump I have somewheres around here that's low press. for carbs and give it a go. Noisy as it was. Thanks to all for the insight.

Question now I guess: with lower pressure pump, do I keep the way it is with a return line, or not?

p2

[mreid]

The info in this thread is at odds with my experience. I have had several vehicles where the EFI was replaced with carbs and a bypass regulator was used to regulate low pressure to the carb. It works perfectly, the pressure is rock steady, and the pump runs cool. In fact, PMO recommends this approach for all their carbs connected to an EFI pump. Fuel input to regulator input, return line to regulator bypass, output pressure to carb(s). Easy.

[snbush67]

Agreed with mreid, the pmo fuel regulator is very nice and the only variance I have noticed as that it fluctuates between a half pound of pressure depending on if my tank is full or empty. I set it at 3 and it is always between 2.75 and 3.25. I believe the 911 Pumps fuel at a much higher pressure than the 914. So if anything it should work better on the 914.

[al lkosmal]

Originally Posted by snbush67

Agreed with mreid, the pmo fuel regulator is very nice and the only variance I have noticed as that it fluctuates between a half pound of pressure depending on if my tank is full or empty. I set it at 3 and it is always between 2.75 and 3.25. I believe the 911 Pumps fuel at a much higher pressure than the 914. So if anything it should work better on the 914.

+1

regards,
al

[porschetub]

Originally Posted by pSquared

Curious, but not surprising. Ran it w/orig. fuel pump and reg for a number of years & seemed to do o.k. Been off the road good long while, but may be excess fuel pressure one of the reasons why died on me back when.

None the less, very informative and helpful info. Gonna dig out the fuel pump I have somewheres around here that's low press. for carbs and give it a go. Noisy as it was. Thanks to all for the insight.

Question now I guess: with lower pressure pump, do I keep the way it is with a return line, or not?

p2

No need to use the return, cap it, or the expensive PMO regulator ,the holley low pressure model pump and their low pressure regulator will do the job nicely,not sure about the Facet as I have never used one.
Yea some of the old hp pumps may work for a time but i don't see the point ,you may have an ok running motor but you risk ''bore washing'' which will cause piston ring breakage and excessive ring land wear thats the facts .