Fuel Pressure Regulator (no Fuel return question) (3 Viewers)

[Boaf 32]

Fellow LC'ers,

1972 LC with Weber 38 / 38. I have no fuel pressure regulator or return fuel line to the tank. I can set one up (done it before).

The question: If a fuel pressure regulator is installed with no return line to the tank, what happens if there is no "overflow (return line) for the additional 2 - 4PSI? Is this a good idea to install with no return?

I have read threads where regulators were installed (like the one linked) and no return line.

Thanks

Boaf

 

[pjohnson]

Why do you need one?

Stock mechanical pump works fine with a Weber.

Before I went back to OEM carb and pump, I had an electric pump and regulator feeding a Weber. There was an inline regulator and no return. It always seemed to run rich no matter what I did. Hence the reason I went to OEM.

 

[Boaf 32]

I have no in-line regulator, stock pump and the Weber 38 / 38 with 155 Jet, and 60 Idle jets. Also down sized to 145's, same. It runs very rich, black exhaust. I checked the pressure and get 6 PSI, for the recommended Weber 3 PSI. Hence, my question about return. What happens to the extra fuel when the pressure is reduced by 3 PSI?

Right now, the fuel just goes out the exhaust. Thanks.

 

[ryanwk628]

The pump creates flow and the resistance in the system creates the pressure. A regulator will put a resistance ahead of the carb and create a pressure drop across it, reducing flow. This gives you an element of control. There are adjustable inline 1 to 6 psi regulators for pretty cheap. Mr Gasket makes one.

 

[Boaf 32]

That's perfect, thanks!

 

[hobbes]

When I had that setup, and lived in a hot climate, I struggled with vapor lock. If you run into that, there's a metal inline fuel filter with a return outlet that you can run back with minimal effort to help keep the fuel cool. Found on the shelf of your local Autozone or the like.

 

[Boaf 32]

When I had that setup, and lived in a hot climate, I struggled with vapor lock. If you run into that, there's a metal inline fuel filter with a return outlet that you can run back with minimal effort to help keep the fuel cool. Found on the shelf of your local Autozone or the like.

View attachment 2142145

Thanks, I like that. I bought a similar one for a Jeep, but it just didn't work as well as hoped for. But that is a nice clean set-up

 

[hobbes]

My 1974 was hacked back when I first got it. It struggled with vapor lock (hot environment, no fuel return, cheap electric pump). Years later someone on here recommended that filter as a fix to keep the fuel circulating and allow for heat expansion after the truck was turned of. I think it is a Jeep filter. I had no further issues with it until I went to my 1987 OEM setup (carb and return on the OEM pump).

My Weber ran great. Just used a lot of fuel. 8-10 mpg, as I recall. I remember playing with the jetting. But as I said, it ran great. The used engine I bought came with a factory carb so I decided to give that a shot. I’m around 14 mpg now (other changes in there like dizzy).

Good luck.

 

[brian]

I have no in-line regulator, stock pump and the Weber 38 / 38 with 155 Jet, and 60 Idle jets. Also down sized to 145's, same. It runs very rich, black exhaust. I checked the pressure and get 6 PSI, for the recommended Weber 3 PSI. Hence, my question about return. What happens to the extra fuel when the pressure is reduced by 3 PSI?

Right now, the fuel just goes out the exhaust. Thanks.

the rich running is a result of the weber, not fuel pressure.
the several times i tryed adjustable regulators, they proved to restrict flow volume too much. they were fine around town but on the road the weber would starve.
i'll take a vacuum secondary over a synchronous two barrel any day.

 

[Dizzy]

I wonder if the return line can be used to drop the pressure to the needed 3psi?

My Nissan 720 has an OEM return line external to the carb, so my Weber in there gets gas that is that much fresher. It would be a real neat salvage yard find to get a hold of that piece of plumbing. However, you might just get a fuel line tee somewhere, and place the proper orifice (like a carb jet) in the rubber return hose.

Someone chime-in if they measured it and the stock mechanical fuel pump delivers consistent pressure regardless of engine rpm, I'm curious.

If your gas mileage is poor, start with valves, spark, and vacuum gauge, then tune your carb so it gets proper air/fuel mix. I just put in new Denso plugs (replacing the wider gapped Autolites that were in there) and OEM wires today, and the engine isn't stumbling with the throttle opening, and the exhaust is much clearer.

 

[hobbes]

This is a good Weber thread if you haven’t scanned through it yet: Weber 38 DGAS : info + settings + tuning

 

[Boaf 32]

I wonder if the return line can be used to drop the pressure to the needed 3psi?

My Nissan 720 has an OEM return line external to the carb, so my Weber in there gets gas that is that much fresher. It would be a real neat salvage yard find to get a hold of that piece of plumbing. However, you might just get a fuel line tee somewhere, and place the proper orifice (like a carb jet) in the rubber return hose.

Someone chime-in if they measured it and the stock mechanical fuel pump delivers consistent pressure regardless of engine rpm, I'm curious.

If your gas mileage is poor, start with valves, spark, and vacuum gauge, then tune your carb so it gets proper air/fuel mix. I just put in new Denso plugs (replacing the wider gapped Autolites that were in there) and OEM wires today, and the engine isn't stumbling with the throttle opening, and the exhaust is much clearer.

So the question to everyone: "What happens to a Weber that runs best on 3PSI when you supply 6 PSI?"

I removed the 38 / 38 just after running it and there is a gas puddle in the Intake Manifold under the Carb. no leaks anywhere, new jets and yet puddle with black smoke and rich smell.

Thanks all,

Boaf

 

[JohnnyC]

"What happens to a Weber that runs best on 3PSI when you supply 6 PSI?"

It pushes past the float valve .... fills the bowl... dumps into the air correction jets

a well maintained weber will not have this happen... hence most people don't have a regulator