Before I buy another fuel gauge

[HawkX66]

I have a Mallory 29387 (4309) fuel pressure regulator on my motor. I can't get it to regulate to less than 12 psi. Before I waste my time and money installing another one, could my problem be a return line that is too small? It seems like it still should be able to regulate the pressure down at least.
What I have: Spectra stock replacement fuel injection tank with internal 50gph/190lph pump. Obviously not high volume. I'm using the stock hard lines 3/8" feed and 1/4" return. I'm running them both to the regulator which I have installed where my mechanical fuel pump would be and then up to the carb. Holley 850cfm dp. Two corner idle. ~14.0:1 afr. I installed an Aeromotive gauge on the fuel feed tube last night to make sure my cheaper Fragola one on the regulator wasn't the problem. The motor runs great except for two things. One: It floods so that when I go to start it, I need to hold my foot to the floor. Everywhere else it runs great. Two: I get a small lean back fire when I step on the gas. I think I need a bigger squirter to fix that though. 35 now. I'm running an AFR gauge so I have a pretty good idea what's going on.

https://farm1.staticflickr.com/872/41194898654_3bff35fd27_z.jpg (https://flic.kr/p/25LfCam)

[big gear head]

I had this problem several years ago when working on a '68 Camaro with a 396. I put a high volume electric pump on it with a bypass regulator. I thought that the #8 supply line and the #6 return line would work fine, but it didn't. Same problem that you are having. I couldn't get the pressure low enough. I had to install a #8 return line and then everything worked great.

[livettes]

Double check to be sure the nipple of the gauge is not screwed too deep into the regulator. They can sometimes block the travel of the diaphragm as well.
Jamie

[HawkX66]

I had this problem several years ago when working on a '68 Camaro with a 396. I put a high volume electric pump on it with a bypass regulator. I thought that the #8 supply line and the #6 return line would work fine, but it didn't. Same problem that you are having. I couldn't get the pressure low enough. I had to install a #8 return line and then everything worked great.
That was my gut feeling. 1/4" just seemed too small. The funny thing is, or not so funny I guess, is that the tank's sending unit has a 1/4" return. I might have to drill for a bulkhead fitting so I can up the size. I was just thinking also, the 1/4" is probably fine if you're actually running fuel injection.

Double check to be sure the nipple of the gauge is not screwed too deep into the regulator. They can sometimes block the travel of the diaphragm as well.
Jamie
Thanks for that Jamie. I'll definitely check it out first.