Steve, I used a stock Mazda 1986 fuel pressure regulator, two NAPA 2P4028 fuel pumps in parallel, and an Andair duplex fuel selector valve. The fuel lines are -6 (3/8") except that the fuel return to one of the tanks has an additional 3 ft of -4 (1/4") aluminum tubing. The fuel pumps each move 47 gal/hr against a 7 psi head. The fuel pressure in the rail is 38 psi when either pump is running. The current draw from either pump is 6 amps. When both pumps are running, the fuel pressure in the rail is 39.1 psi when the tank without the additional 1/4" return tubing is selected and 39.6 psi when the tank with the additional 1/4" return tubing is selected. The current draw from both pumps is 12 amps. Since with my setup running both pumps only increases the pressure by about 1 psi, and the 3 ft of 1/4" tubing only adds about 0.5 psi of back pressure with both pumps running, it might be worth checking for a restriction somewhere in your system. Steve Boese From: Rotary motors in aircraft <flyrotary@lancaironline.net> on behalf of steve Izett <flyrotary@lancaironline.net> Sent: Friday, March 17, 2017 3:44:46 AM To: Rotary motors in aircraft Subject: [FlyRotary] Fuel Pump and Regulator Hi Guys I fired up my secondary fuel pump for the first time today and was met with what I didn’t expect. Instead of seeing a blip in the fuel pressure, I had a 10psi increase and high current draw from the pump which blew its 10amp fuse. I’ll up the fuse as its too low me thinks. I used an old fuel regulator I had on a rail. It was of a Toyota 4AGE engine of about 135hp. Seems like its not able to bypass enough fuel with both pumps running. I think I need to install a higher power adjustable regulator. What experience do you guys have with turning both pumps on simultaneously? I’m putting a pressure switch in the circuit to turn on the backup pump if the fuel pressure drops below a preset level. Appreciate your thoughts and experience. Steve Izett Genesis 4 port EC3 EM3 RD1C in a Glasair Super II RG still nearly finished! -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html
Steve,
I used a stock Mazda 1986 fuel pressure regulator, two NAPA 2P4028 fuel pumps in parallel, and an Andair duplex fuel selector valve. The fuel lines are -6 (3/8") except that the fuel return to one of the tanks has an additional 3 ft of -4 (1/4") aluminum tubing. The fuel pumps each move 47 gal/hr against a 7 psi head.
The fuel pressure in the rail is 38 psi when either pump is running. The current draw from either pump is 6 amps.
When both pumps are running, the fuel pressure in the rail is 39.1 psi when the tank without the additional 1/4" return tubing is selected and 39.6 psi when the tank with the additional 1/4" return tubing is selected. The current draw from both pumps is 12 amps.
Since with my setup running both pumps only increases the pressure by about 1 psi, and the 3 ft of 1/4" tubing only adds about 0.5 psi of back pressure with both pumps running, it might be worth checking for a restriction somewhere in your system.
Steve Boese