Fuel Pressure Gauge Reads Zero

[BoureeOne]

This one has me scratching my head. This is my low pressure line feeding my FiTech Fuel Command Center 2. It is being fed by a Carter Electric Fuel Pump. Carter should be putting out about 5 psi. The gauge is a non-liquid filled gauge that goes up to 15 psi. I have 58 psi from the FCC 2 to the FiTech 600. The low pressure gauge always reads zero. I have removed the gauge and quickly turned on the low pressure pump, and fuel shoots out the hole under pressure. I have rotated the gauge facing downward to see if somehow air trapped in the gauge was not letting it read, still at zero. I also have tried two liquid filled gauges, all read zero. The engine runs perfect. I feel like I am somehow missing something simple here. The gauge is mounted on an adapter that is 6an male and female.

 

[BoureeOne]

Does it make a difference that the FCC2 is constantly returning fuel via the return line? Does this mean the Carter pump is basically just filling up the reservoir for the high pressure pump and pumping straight back to the tank? Is this why it is reading zero?

 

[Broncobowsher]

Correct. With a return line it is full flow. If you pinched off the return line the pressure will rise. Not sure if the FCC will be happy with it so I won't recommend it. Pumps don't make pressure, they make flow. Restrictions that slow the flow are what make the pressure.

The Carter will be completely happy running full flow. There is some rumor that they need a restriction or they burn up. They won't. Even though they are flowing more fuel they are under less of a load and will run cooler with the steady flow of fuel through them. Now if it was a cheap impulse pump (they knock when they run, sound like a slow woodpecker), those could burn out with open flow. The impulse pump is like a mechanical pump but instead of a cam lobe cycling the diaphragm there is a coil (solenoid) and it is cycled by a set of points.

 

[BoureeOne]

Correct. With a return line it is full flow. If you pinched off the return line the pressure will rise. Not sure if the FCC will be happy with it so I won't recommend it. Pumps don't make pressure, they make flow. Restrictions that slow the flow are what make the pressure.

The Carter will be completely happy running full flow. There is some rumor that they need a restriction or they burn up. They won't. Even though they are flowing more fuel they are under less of a load and will run cooler with the steady flow of fuel through them. Now if it was a cheap impulse pump (they knock when they run, sound like a slow woodpecker), those could burn out with open flow. The impulse pump is like a mechanical pump but instead of a cam lobe cycling the diaphragm there is a coil (solenoid) and it is cycled by a set of points.

You are 100% correct. I found a 6AN end cap. I capped off my return from the FCC2. The pressure was 5psi on the gauge. I figured I was missing something simple. The FCC1 did not work like this. The fuel from the low pressure pump just sat there and supplied the high pressure pump. This is why they had issues with it overheating and boiling the gas in the FCC1. Now the FCC2 circulates the fuel from the low pressure pump, around the high pressure pump and back to the tank. Much better system. Thanks for your help....