Having a little problem, need help please

[minendrews68]

I've got a Holley fuel regulator with bypass. I have my fuel lines rubbing from carb to tank with steel lines. My problem is that my fuel pressure at idle will run at 10.5 psi. I have backed the adjustment screw out to where there's about 5/8" sticking above the lock nut. No matter how far I run the adjustment in or out, there's no change in pressure.
Does anyone have any suggestions? I have also used another new gauge same results. Im stumped!

Thanks
Carl

[minendrews68]

OK, checked again this morning and found that with the fuel pump running, engine off, I've got 7 psi. Start the motor, it jumps to 10.5 psi and holds there. This doesn't make sense to me.

[rchaskin]

I'm not trying to be a smart a, but is the flow thru the regulator in the right direction?
We do lots of pneumatic where I work, and a regulator turned backwards does the same sort of thing.

[minendrews68]

Your not a smart a$$, lol, I'm telling you if that was the problem, I would gladly accept my ignorance! Yes, it is going the right direction. Although, after I took it apart I can't see what difference it would make. That thing is a pretty simple mechanism. Here is what I've tried so far:

I know that the adjustments should be made while running, I was just trying different things.
It's just that with the engine not running, and the fuel pump on I get 7 PSI. Start the engine it goes to 10.5 PSI. That in itself throws me for a loop. I have tried adjusting pressure, both with the engine running and not running (fuel pump on). Here's what I've done so far.

I took the fuel regulator apart, it was pretty clean! I put it back together, blew into the end the fuel comes in, blocked off the exit and air came out of the return port. I even tried adjusting the screw while under pressure. It seemed to work.
I then took a compressor and blew air back through the return line, and could hear air coming out of the tank. (So I think that's not clogged.)
I looked at the float levels, first, with the engine not running. But fuel pump running, fuel level just trickled out of the bottom of the sight hole.
Started the engine and looked at the fuel level at the sight plug, and it was just trickling out just as before, only at 10.5 PSI at the gauge.
I'm going to go get another gauge and see if mine is bad to see if that's the problem.

Are you saying the pressure regulator should be adjusted with the engine running, at idle or above idle? I've tried at idle, and the gauge never moved no matter how far the adjustment screw was moved. I'm about frustrated!! Thanks for your help.

Carl

[rchaskin]

Sounds like you tried everything I would have.

You may have to call Holley Tech support.....

[andrewb70]

Carl,

I don't know much about this carb stuff, but I can possibly explain why pressure jumps when the engine is running. With the engine off, the pump is seeing battery voltage, probably around 12.5v. As soon as you start the engine the alternator is putting out closer to 14 volts and the pump runs faster and hence more pressure.

Andrew

[minendrews68]

Randy,
I've talked to 3 different Holley tech's, none seem to have a answer, well, they had a answer, but it didn't work. I took the regulator apart again today and it still looks good inside. The diaphragm is still pliable. I ran air through the bypass back to the tank again, and it seems like it might take a little more than 10 psi to get the air back to the tank. Hopefully I'm on to something.

Andrew,
That makes sense, it's these other things that doesn't... Why I can't adjust the pressure with engine running or not makes me think the fuel is deadheading and not returning to the tank via the bypass. I'm now thinking it's taking too much pressure to get the fuel back to the tank. (at least more than 10.5 psi anyway). Luckily with the engine at idle (gauge reading 10.5 PSI) the fuel is barely coming out of the sight hole with plug removed.
Man, this is crazy. I've read on a few more forums of other people having this problem, but it seems most didn't have the return. Never found an answer though

[minendrews68]

Ok, this is my thoughts now. After taking my regulator apart again, still finding nothing I can see that's wrong. I took my air hose and blew air through the bypass again, it seems like it takes a good deal more than 10 PSI to blow through to the tank. I'm thinking there's got to be somewhat of a blockage there even though increased pressure will go through. I'm thinking if it takes more than 10 PSI o get the bypass to work it won't until I find blockage. I'm taking the car to a friends garage Monday to tut it on a lift and see if my thoughts are right. I'll let everyone know what I find out.

[67 455 Bird ragtop]

What size are your feed and return lines ??? Sorry if I'm asking the obvious.

[minendrews68]

Feed is 3/8", return is 5/16" i believe.

[67 455 Bird ragtop]

Feed is 3/8", return is 5/16" i believe.
Return size should be at least the same size of teh feed if not one size bigger.

[MonzaRacer]

Doubt fuel line or return size is issue if its carbed and your not running a 50-60 psi pump. Sounds more like there may be a restriction inside the regulator. MAKE SURE YOUR ADJUSTING IT RIGHT DIRECTION ALSO . And make sure return line is free back to tank.

[nevasuma]

i had the same problem. To fix the problem I first changed the return to 3/8. then I bought this https://www.aeromotiveinc.com/product/efi-2-carb-dual-fuel-pressure-regulator/.

It is a dual regulator. first it drops the pressure down to 12 psi, then the second part drops it down to what you want. with mine it was 6.5 psi.

[Michaelangelothepayner]

That aeromotive looks very nice but it would be a lot cheaper to just run a regular dead head regulator after the bypass regulator.

[minendrews68]

Man, all good ideas. Currently I'm thinking of changing everything to efi. Of course, the efi comes last, after I have the other components in place. I'm thinking of a Tanks Inc. tank, Walbro 255 pump and fuel gauge. I'm going to use a Holley billet fuel regulator that regulates between 4psi to 65 psi. This regulator could regulate fuel pressure down to the carb specs for now and then be able to handle the high pressure of the efi. Anyway, that's what I'm thinking...

[Curt C]

The return line should be the same size as the feed or larger. The restriction is keeping the floor above 7psi.

[cornfedbill]

I worked in fuel injection at Bosch for years. I would increase the size of the return line to 3/8" and make sure there are absolutely no restrictions.

Andrew is right about the voltage change affecting the fuel pressure. 12.5V versus 14V can make a big difference in some pumps.

If you are backing the screw out, it sounds like you are adjusting it correctly. If it stops changing the pressure, then you have completely unloaded the spring adjustment. There is nothing more you can do there.

Again, open up the return line. It sounds like it is restricting the flow and causing the high pressure. That is what I would do if it were me.

[mitch_04]

Could you try just running a 3/8 line return into an old gas can for a quick test to see if the return is your issue? Quick and easy way to see if that's the issue, if it is then you can run a new line back to the tank, if not then you start in another direction.

[minendrews68]

I'll tr the line change and see if it helps