Datsun Roadster Forum-311s.org

New build (1968). 1600 stroker. Mikuni/Solex 44’s. I’ve placed the pump, regulator and gauge as shown on the inner passenger fender before the carbs. Blocked the fuel return after the carbs. Thought this would regulate fuel to the carbs but the gauge reads zero no matter how I adjust the regulator. I’m thinking this setup is fundamentally wrong but the engine runs pretty good from idle to redline. Seeking advice on how to plumb everything. Should the regulator and gauge be after the carbs?? Or should the gauge be placed before the regulator? I’m trying to regulate the carbs to 4 or 5 psi. Also think I should be using the fuel return to the tank.
Holley Mighty Mite 4-7 psi pump
Summit Racing G3033B regulator
Summit Racing pressure gauge.

The gauge should be between the regulator & carbs. Don’t know about the return line, to start I’d probably clamp it off until you get enough pressure for the carbs, then remove the clamp to see if the pressure holds.

Sounds like you either have a defective gauge, the pressure is very low or something is wrong with the plumbing. Clamp off the hose(s) to the carbs & see if the gauge shows pressure.

Peace, Pat

Sounds OK it's really about flow to the carbs
? Is the pump hooked to a relay with alt amps or other as the trigger.... if just to the ign side ,you wreck and the pump still going ,leaking

Pump is run off relay with trigger from coil positive. So pump runs whenever ignition is on. Eventually I will wire the relay to include an oil pressure or alternator trigger.

Electric fuel pumps of that type do NOT pull fuel, it needs to be back at the gas tank pushing the fuel! Trust me on this.
Dave

Well, I guess my options are to find a pump that can pull from the front or move this pump back by the tank. In either case, I assume the regulator and pressure gauge go before the carbs? The current pump must be pulling enough fuel currently because the engine is running but I’ve only run it in the garage. Haven’t tried driving it yet. I have read that pumps should always push fuel, not pull. Maybe the mechanical pump is better at pulling fuel?

Dave is correct... that pump is not designed to pull fuel that far, it's a pusher. Find a place near the right rear wheel and mount it to the frame there in as protected a spot as you can so it can push. You want your guage after the regulator to show you what pressure you have in the line after you regulate it down, right? Then to the carbs. 2-3lbs is all that's needed. I don't think you need the return, but it should be closed off I'd think as it leaves an open vent to the tank (?).
I've used similar pumps for years, and still do to feed my swirl tank for the high pressure EFI pump. I suggest you carry a spare as you never know when you might need one... I've changed mine on the side of a mountain road when I was running carbs. Best $30 you'll ever spend. Thing about fuel pumps... no pump, no go! I carry back ups of both now.

Move the pump only to as close as you can to the fuel tank, cut the steel line and put a ferrule fitting on each piece of the metal line and pinch the line a little on each side of the ferrule fitting so it will not move when you push the fuel hose onto the metal line. Clamp it and secure the pump with with soft mounts so not to amplify pump noise. Leave the pressure regulator near and down stream of the filter and place the pressure gauge between the regulator and carburetors. Don’t forget to install a fuse on the wiring going back to the pump and don’t worry about using a relay for the pump. Keyed ignition at the coil is more than enough to power the pump. You also don’t need to worry about a fuel pump cutoff switch, that really for high pressure injector pumps that are running pressures upwards of 50 PSI. If you wreck your car so badly that fuel line are torn apart and fuel is flowing you have much larger problems than that.
Dave

No one, Manuf. Wise ran a electric pump with a carb
for safety reasons , it's easy to cut a fuel line or hose in a frt end crash ! it's usually by a computer off the degree wheel that kills it

Thanks for all the replies. Dave Premo- appreciate your plumbing and layout recommendations. So, easy enough to re-route the pump I have. Got me thinking why I was using an electric pump in the first place, other than it came with this project that I acquired. What about using an original mechanical pump instead? The advice I got from the engine builder was to use the electric pump with a regulator to tune the pressure to the Mikuni carbs. (4-5psi). Will a mechanical pump perform the same way? Would simplify things, kind of, but original pumps are pricey. Thoughts?

To feed the pair of nominally 3.5 PSI-seeking Solex 44PHH, I use a Carter P90091 rotary vane 12V electric 15 GPH 2-4 PSI pump.

I located the cylindrical pump body on the top of the front passenger side frame rail, near the factory metal gasoline supply line.

The mechanical pump mounting therefore is blanked.

The Carter rotary vane pump has a replaceable metal filter ahead of the pump draw, and is designed to self-prime.

I installed a 10G inertial electrical power cutoff in the event of serious impact.

I have never had an issue with pump priming, Solex over-pressure or starvation -- or thankfully with a high G event. Knock wood.

So the pump I recommend is the Facet cylindrical pump with a built in filter 2.75-4 PSI unit, which is exactly the same as the factory Nissan 73 240/260 pump that was back by the fuel tank. They come with a kit to rubber mount them and are significantly cheaper than the OE Nissan ones. Facet part number FAC-477060 is the one I recommend all the time. It can deliver up to 34 gallons per hour. A very impressive pump. They are OE on all kinds of older Europe vehicles and air planes and boats as well.
Dave

Pusher in theory is probably better but I’m here to tell you I’ve been running a Carter 4070 as a puller for over 10 years now mounted on passenger side front frame. I’ve never had luck with the Holley regulator as you, they don’t seem sensitive enough. My el cheapo Mr gasket dial works just fine. Just sayin.

On a road-trip years ago my pump failed, so it was far easier for me on the road to make it a puller system than crawling under the car on a trip. It worked but never would never fill the filter bowl like it did when I made it a pusher. I also used one of the cheap pressure regulators with a dial on it. But when I had time I purchased a Hitachi 240Z pump online for $70.00 a bargain even at the time. Much quieter and superior quality to the cheap aftermarket ones.
Dave

Great info on the different electric pumps. Thanks for everyone’s responses. No comments on using a mechanical pump however. I’ve always used a stock mechanical pump on my ‘73 Z car with never a problem. It does have an electric pump near the tank as stock configuration. I felt like it would be far more convenient to mount the electric pump in the engine compartment on the roadster. Push vs pull still confuses me. But the Holley pump I have does say to mount it no farther than 12” from the tank so I guess it is a push type.