I have a Holley red pump with a Holley 4/12 - 9 psi regulator. This regulator is not a bypass style.



When the engine is cold:

The pump outlet pressure is about 8psi The pressure after the regulator is about 5.5psi

When the engine is warmed up:

The outlet pressure of the pump is about 6.5psi. The pressure after the regulator will not go higher than 3psi.

The pump is getting 14 volts.



It's been like this since the engine was started. Last weekend the thing didn't want to idle. I looked at the pressure and it was barely above 0psi. So the problem seems to be progressing.

I'm using the stock tank at the time. I have a 5/16 line from the tank to the fuel filter with a 3/8 line from the filter to the pump and 3/8 hose, -6AN Hose or -6AN tubing after the pump all the way to the carb. I have a 90* elbow on the inlet of the regulator. The only other 90* bend is at the carb inlet. All other bends are about 135*. The filter is one of the MR gasket universal deals with nipples for 1/4, 5/16, and 3/8 hose. The fuel line does not run near any significantly hot spot. I can touch and hold the line without burning myself. It has nothing to do with the fuel level in the tank. The results are the same if the tank is half full or almost empty. I've used different gauges to rule out a faulty gauge.

Does this sound like a bad regulator? I want to have the pressure at 5.5psi because that is what the Edelbrock manual says is most efficient for the carburetor. I realize that the system isn't ideal but I don't understand why I can't get 5.5psi at the carb if I have 6.5 at the pump outlet. I'm not even able to achieve the 4.5psi minimum of the regulator!



I've contacted Holley's e-mail tech support. As someone who provides e-mail and phone tech for vintage BMW motorcycles, I'm not impressed.


Lawrenceville, GA

Try testing it with the gas cap off or loose.

Best regards,



Paul Menten

Meridian, Idaho

I'm suspecting a faulty fuel pump.  Does the fuel pump get hot to the touch after it runs for awhile?  The fuel filter also sounds like one of the very small units that has a built in flow restriction which in turn could be causing the pump to potentially overheat or starve for fuel.  I'd suggest a larger flow fuel filter and see if that helps after doing the afoementioned 'fuel cap off' test.

Lorena, Texas (South of Waco)

Thanks for the ideas!

Here is what I did.  I temorarily eliminated the fuel filter by replacing it with a barbed fitting and installed a guage at the regulator inlet.  The filter is clean so I don't fear removing it for this test.  I don't plan on driving it until the problem is fixed.

When cold the regulator inlet pressure was 7psi, outlet adjusted to 5.5.  As it was warming up the pressure on the inlet slowly dropped to 2psi.  I then unscrewed the gas cap.  Nothing changed so I turned it off.  I touched the pump and while it didn't burn me it was pretty toasty.  I held onto it for a few seconds and didn't get any burns.

So I think one of 3 things is happening.

1.  The tank configuration just isn't able to properly supply the pump.  Does anyone know if it is a syphon?  The line goes in the tank at the to of the tank.  I'm fairly confident that it is a syphon.  The Holley instructions say that it will work with a syphon feed.  The pump inlet is below the lowest part of the tank.

2.  The pump is defective.  It is rated to provide 7psi so it seems to be working properly when it's cold.

3.  The warmest point of the fuel line is at the fuel pump block off.  I wanted to bypass this with some rubber line but I don't have any fittings on hand to do so.  It can't be any warmer than it would be if a mechanical pump was installed.  Does anyone know the temperature at which it becomes a problem?  A friend of mine has one of those infrared thermometers.

So anyway, it looks like the regulator is eliminated as the problem.

Lawrenceville, GA

Where is your pump located? Usually they work better as a pusher than a sucker, so the pump should be located at the rear.



I may have misunderstood, but you say the line is the hottest at the location of the mechanical pump? Is this just from engine temperature? If so, I doubt that is the problem but wrap something (aluminum foil) around it. You could also split a piece of rubber hose and put that on the steel line.

54 Victoria 312;  48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ

The pump is under the cab.  The tank is in the cab, behind the seat.

I designed a fuel pump block off with a fuel line mounting tab built into it.  It provides a ridgid mount for the fuel line.  It is the engine heat warming it up in that area.

I found some stuff in the garage and was able to bypass the block off.  Still the same pressure drop issue.  So that eliminates the block off as the problem.  Now it's down to the tank or the pump.  I guess I could rig a gas can with a gravity feed to see if the tank might be the problem. 

Lawrenceville, GA

Charlie,

             I've had lousy luck with Holley regulators. I am not sure that this is your problem, but the Summit brand regulators seem to cost less and work better.

Frank/Rebop

Bristol, In ( by Elkhart) 

Here's how I plan to rule out the fuel tank.  I've been working on it for the past week-and-a-half.

I'm almost done.  I need figure out how to get the fuel from the door into the fuel cell, pump mounting, get it all painted, and that's about it.  I'm hoping to be able to try it out next week.

So, if the pressure is low when I'm done with this, the pump is all that's left.

Lawrenceville, GA

Looks pretty good Charlie, I just bought a mustang tank that I am going to mount in my 62. Thinking about adding a rolled pan to the rear of the bed and letting the filler come out the rear using a 57 car tag bracket to cover everthing up.

Glen Henderson



Freedom is not Free

Letohatchee, AL

I saw an article on FTE about installing a mustang tank. I would like to have done something like the mustang tank. It is a little lower profile. It requires that the rear cross member be relocated which is difficult on mine since the bed can't be removed easily. The fuel cell is slightly visible from behind but the bumper and license plate do a good job of hiding it. Once I lower the rear it shouldn't be noticeable. Put some pics up when you get it done. I'd like to see how it turns out.

Will you be going to Columbus, Glenn? I'm planning on leaving Friday morning. We could meet up somewhere along the way for the drive. I don't know how you might go but I'll be starting on I75.


Lawrenceville, GA