392 walbro electric fuel pump question

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jimjimjimmy

jimjimjimmy

lobsterman
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I just got the walbro pump and it is rated at 60psi to replace the aeromotive that just died is it all right to use this with a 950 holly I have a good regulator .and will I need to reset the fuel pressure at the regulator im not sure what the aeromotive psi was it was the big pump. I have no psi gague on my regulator that is why im asking thanks all.
 
Those pumps are rated by a "flow curve". The flow-rate depends on the operating pressure, and the voltage supply. Sounds like you have a carburetor, unless your slang means "Holley Commander 950 EFI". Even the smallest EFI pump should put out ample flow-rate at the ~5 psi pressure that a carburetor needs.
 
it is a carb bill so your sayin this will work on a carb with a regulator
 
you are going to be circulating a lot of fuel through the return if you've matched an efi pump to a carb.
 
I am running a GSL-392 on a carb set up. You will need to have a regulator with return. This pump will support huge HP, 800+ on a NA Carb set up and 600hp on a boosted EFI set up.
 
jimjimjimmy said:
http://www.grumpysperformance.com/FuelFlowDiagram02a1.jpg I don't understand how or why you would put the regulator after the carb what good would this do or am I missin something.
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The diagram is fine like that. It is still bleeding off the FP to 6psi per the diagram. Before or after is fine.

For sure on an EFI application it should be done like that. Your FP will be more stable this way without the possibility of leaning it out.
 
The regulator design will determine if that diagram is useful. If it's an EFI regulator it's just fine providing the injectors, regulator, and return line are sized properly. The injectors are the real "open/closed" valves in an EFI.
Just my opinion but in a carbureted system and running a pump with that much volume I would not run it like that diagram shows. To me, as drawn, the carb's needles are exposed to full flow and the floats may not be enough to close them if it can go 60psi or more. I'd run the regulator before the carb and a return line the same size as the feed line. Because you are limiting the pumps volume so much at idle you amy want to look into a fuel pump management unit to keep it from overheating during long idle or light throttle running.
 
moper said:
The regulator design will determine if that diagram is useful. If it's an EFI regulator it's just fine providing the injectors, regulator, and return line are sized properly. The injectors are the real "open/closed" valves in an EFI.
Just my opinion but in a carbureted system and running a pump with that much volume I would not run it like that diagram shows. To me, as drawn, the carb's needles are exposed to full flow and the floats may not be enough to close them if it can go 60psi or more. I'd run the regulator before the carb and a return line the same size as the feed line. Because you are limiting the pumps volume so much at idle you amy want to look into a fuel pump management unit to keep it from overheating during long idle or light throttle running.
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i agree the return has to be at least as big as the feed. but if you look at all aeromotive return style reg's the feed is on the same side of the diaphram as the feed lines to the carb. so having the regulator after the carb would be no different as i could see.
 
I agree with Mad Dart and 805moparkid. You must have a bypass line back to the tank (or at least the pump inlet) when using an EFI pump. They are positive displacement pumps, which impose a volume flow. They will build up extreme pressure if "dead-headed", making either the pump stall or a line burst.

The diagram shown (www.grumpysperformance.com/FuelFlowDiagram02a1.jpg) uses a "back-pressure regulator", so is downstream of the carb inlet. For safety, it might be smart to also have a "pressure-reducing regulator" in-line with the carburetor. That will keep the carb's needle from being forced open if the back-pressure gets too high. Simple ones have a dial knob and were sold under many brands.

I also am using the same Walbro EFI pump with a carburetor. In my case, the carb is just temporary and I plan to run EFI later, but I wanted to plumb for a carb as a backup. I didn't find a cheap back-pressure reg, as shown so made my own from a cheap Norgen relief valve (McMaster-Carr?) that I added a weaker spring, and adjusted to 6 psi using shop air. It didn't work because I measured 16 psi on my car (relief wide open), so I took out the relief valve and found I got 10 psi just in the return plumbing. I put an in-line reducing reg to control what the carb sees ~5 psi). If you get one of the $45 fuel level senders on ebay, with a 3/8" outlet and 1/4" vent tube as I did, return to the 1/4" tube and you will get ~10 psi back-pressure for your carb. Drop that with an inline reducing reg. That should hold fairly constant since the EFI pump puts out way more volume at 10 psi than your carb will ever use.

Theory - a back-pressure reg controls the upstream pressure, a pressure-reducing reg controls the downstream pressure. wikipedia is your friend.
 
so can I run a line from the return on the regulator back and tee it into the intake side of the pump for now.
 
jimjimjimmy said:
so can I run a line from the return on the regulator back and tee it into the intake side of the pump for now.
Click to expand...

Yes, however some fuel will then be circulating most of the time, getting hot from the pump. That is why most people return it to the tank. Also, you might lose the fuel in the loop above the axle since the carb might allow air in past the needle when the engine is off (like taking your finger off a straw that is holding water). If so, the pump will have to suck air each time you start until it "re-primes" the tubing. I would at least have a fuel pressure gage installed to monitor the pump outlet. Let us know if it works.
 
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