Question Holley fuel pressure regulator...one way check valve?
 

Hi folks,
I have a question regarding the Holley fuel pressure regulators.
I have a Willys Jeep with a SOLEX carburetor. These carbs are infamous for being very sensitive to high fuel pressure. I installed a Holley 12-804 type fuel pressure regulator to keep the fuel pressure to 1.5 psi. I installed a pressure gauge on the regulator to measure my adjustments. The regulator is installed between the fuel pump and carburetor.
It works perfectly and runs great. The vehicle is new to me (just got it running) and I'm encountering a hot start problem. It's flooded after sitting hot for 5 or 10 minutes. I then noticed after a hot shut off the fuel pressure slowly rises on the gauge (takes up to 10 minutes) to over 5 psi. The SOLEX can't handle that and I get a flood condition. I'm assuming the pump, lines, filter, regulator are all heating up (heat soak) and the pressure rises as a result. I would have thought that pressure would bleed back through the regulator and pump back to the tank, but I guess not.
The fuel system is a "dead headed" system: fuel had only one way to go after the pump....into the carburetor.
Question: is the Holley regulator like a one way check valve?
Thanks,
Dave

Sounds like the check valve in the diaphragm pump is in great shape. I'd bet that if you loosened a line between regulator and pump the pressure would bleed off, and that would prove the regulator wasn't responsible for holding the pressure.

Sounds like you need a by-pass style regulator and a return to the tank.

If you don't want to go that route, then try moving the regulator as close to the carb as possible. That way if it has a check valve on the outlet side there will be less fuel to heat soak and expand.

I could be wrong but I'd assume the pump allows some kind of slow pressure bleed off, they have to have a check valve to operate properly ... but often have a bleed of some sort to prevent just such issues.

Yes, I believe it is a one way check valve, so what I did was make up a temporary hose barb, sealed up the end, drilled it with a 0.030" orifice, and plumbed it right to the gas line BEFORE the fuel pump. My thought is when the Jeep is running, the orifice is small enough so that not alot of pressure bleeds off (the pump can supply LOTS of pressure which is why I run the regulator in the first place) and the carb stays full. When I shut it off, the pressure will bleed off back into the fuel supply line, back to the tank through the same orifice. The regulator has two outputs, so I ran the hose barb from one of those outputs.
I'll update when I test it...
Thanks!

Sounds reasonable ... yep the pump inlet would be pretty much the same as the tank.

Update: The modification worked; the bleeder orifice does immediately bleed off pressure to the carburetor when the engine is shut off (pressure goes to zero). When running, I lost just a little bit of pressure so I adjusted the regulator a tiny bit to get my pressure back to 1.5 psi.
Now, after shut off and a heat soak for a few minutes, I can restart in the hot state and it instantly starts right up. No more flooding.
In the picture you can see the pump with the output on the top left going up to the filter and then regulator. One output of the regulator goes to the brass block attached the carb with a banjo bolt. The far side of the brass block has the fuel pressure gauge. The near side of the regulator has the brass hose barb with my custom orifice to which the rubber line directs the excess pressure down to a "T" in the inlet side of the fuel pump.
(the other steel lines are vacuum lines from the bottom side of the fuel pump for vacuum wipers.)
Thanks for the comments!

Nice work ... looks like fuel lines to some kind of jet engine :)

Just saw this..

Kudos on finding a solution. Good idea! Having the pressure gauge installed seems to have paid off for more than setting the regulator!

I'm curious why the regulator had two outputs? Is this typical for all regulators?

All I know is I remember using this type of Holley regulator in the 80's and they seem to be the same 35 years later. Kinda big and bulky with two outputs, but easy to adjust and seems to be nice quality.

Wouldn't the two outputs be for dual quads? Very nice set up BTW. :)