Fuel Pressure Reg Issue or other Issue?
11-22-17, 11:11 PM
#1
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Fuel Pressure Reg Issue or other Issue?
While tracing another issue I have been having with my rotary, I checked fuel pressure, which opened up a new issue I didn't know I had for 3 years. I have 74PSI Fuel pressure at idle, and it drops to 68-70PSI at wide open throttle at redline. Removing the vac line to the regulator makes no change, and I am getting vacuum to it. At fuel pump prime, I am getting 55psi, and as soon as the pump shuts off, my pressure drops to 38 and holds there with the engine off. I connected the fuel pressure gauge tee'd into the fuel line between the fuel filter and fuel rail, so a plugged fuel filter would give lower pressure since I am reading fuel pressure after the filter.
Background info, this is mainly a S4 TII engine in a 93 B2200. The B2200 was originally EFI, I originally swapped a stock S4 NA motor into the truck in 2014, ran the original fuel pump for a few months, I found the fuel pump (which had 180,000 miles on it), was not supplying enough fuel pressure when the secondaries kicked on, so I changed it for a Supra fuel pump, ran that for a year, then I changed it out for a 340LPH pump last spring. I swapped the S4 TII engine in last winter.
I am running the stock fuel pressure regulator, and no pulsation dampener, stock B2200 rest of the fuel system, including the filter. Stock size rubber fuel hoses as well
I am thinking the crazy high fuel pressure is due to my fuel pump flowing more fuel than the regulator can handle, but has anybody else had this issue? I mostly see people add an adjustable fpr to increase fuel pressure for larger injectors, etc... Not due to a larger flowing pump.
Background info, this is mainly a S4 TII engine in a 93 B2200. The B2200 was originally EFI, I originally swapped a stock S4 NA motor into the truck in 2014, ran the original fuel pump for a few months, I found the fuel pump (which had 180,000 miles on it), was not supplying enough fuel pressure when the secondaries kicked on, so I changed it for a Supra fuel pump, ran that for a year, then I changed it out for a 340LPH pump last spring. I swapped the S4 TII engine in last winter.
I am running the stock fuel pressure regulator, and no pulsation dampener, stock B2200 rest of the fuel system, including the filter. Stock size rubber fuel hoses as well
I am thinking the crazy high fuel pressure is due to my fuel pump flowing more fuel than the regulator can handle, but has anybody else had this issue? I mostly see people add an adjustable fpr to increase fuel pressure for larger injectors, etc... Not due to a larger flowing pump.
11-23-17, 10:55 AM
#2
rotorhole
what pump are you running? you'd have to have something insane like a 400lph pump to cause such a huge pressure rise.
also keep in mind, once you fix the issue you will have noticably less fuel in your tune across all RPM ranges.
also keep in mind, once you fix the issue you will have noticably less fuel in your tune across all RPM ranges.
11-23-17, 10:27 PM
#3
11-23-17, 10:36 PM
#4
rotorhole
thats still far too much fuel for the stock fuel pressure regulator and likely could be your problem.
you need to omit the stock FPR and put in a larger volume regulator RRFPR on there.
you need to omit the stock FPR and put in a larger volume regulator RRFPR on there.