I'm running a Holley 12v electric fuel pump with a Holley regulator on my flathead. With the current setting on my regulator, fuel pressure starts off about 6 lbs. when the engine is cold, and eventually drops to about 2 1/2 pounds after the engine warms up. If I set the regulator at 2/12 pounds when the engine is cold, it drops almost to 0 when the engine warms up. Shouldn't fuel pressure be constant regardless of engine temperature? I'm guessing I may have a problem with the regulator. Any thoughts? Sorry if this is a stupid question. Thanks.
Is this a fluid filled guage, they will change readings with heat if mounted underhood,this is a common complaint.
wheres the gauge mounted. Underhood or in car. Tube inside gauge would stay constant temp in car and vary enough to change reading if mounted on engine. like sdluck said
Is the pump exposed to exhaust system heat? If so, move it or get some shielding around it. What does the voltage read at the pump? It should be right at battery voltage read at the battery. If it's a volt or so down, install a relay controlled by the old pump feed wiring. Set the relay close to the pump, feed it with 10 gage wire, feed the pump with 14 gage wire from the relay. The relay should be inside the car and the pump outside the car. Biggest reason Holley pumps burn up is low voltage. A touch over one volt low is 10% down. Looking at it in percentage figures makes it easy to see why pumps burn up. My old pump that burned up had 11 volts at the pump and 12.3 volts at the battery with the engine not running. A relay installed as noted put 12.3 volts on the pump. Another place to check is the internal pump regulator. Check to see if it's stuck and if so, remove the piston and clean the bore with used 400 grit wet and day sandpaper. Clean and re-assemble. I had a stuck pump regulator do very much what you described in your initial post.
The car is a 32 Ford 5 window. The gauge is a liquid filled Moon gauge. It's installed on the fuel block which is mounted to the firewall on the driver's side. Currently the car has no hood, so it's hard to believe that enough heat would build up to change the reading on the gauge. If it is heat changing the reading on the gauge, does that mean that the gauge is reading inaccurately once it heats up or is the pressure really at 2 1/2 pounds when the gauge is hot? Should I get another gauge that is not liquid filled? I'm a little confused. The fuel pump is mounted inside the frame rail on the right side about 18" to 2' forward of the gas tank. Part of the right muffler is adjacent to the pump, but there's about 8 inches of space between the muffler and the pump. The pump is already controlled by a relay mounted in the trunk, so I don't think it's a voltage problem at the pump.
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