I'm having trouble controlling the fuel pressure on the tbi / carb'd system on my K5. The motor does not run yet, I'm trying to get everything ready so I can crank it.
This is a 91 K5, I'm using the original tbi tank and fuel lines with a new GM replacement pump. At the motor I have a Holley 750 carb using a Barry Grant bypass return pressure regulator with a Holley 15psi pressure gauge on it. The fuel system still uses the overflow return line back to the tank.
When I first hooked up the battery and turned on the pump I couldn't control the pressure, it had a constant 13psi no matter how I adjusted the regulater. I bought a rebuild "kit" (just a diaphram and spring) and new gauge thinking one of the two was dead from sitting up for a few years.
After replacing parts I still had the same problem, a constant 13 psi (gauge close but not pegged). At this point I figured the return line was plugged - dirt dobber, trash, etc.. Today I blew air through the line and it appears to be clear. Now I can only muster 5.5psi.
I can make adjustments down in pressure but it will not go any higher (I'm trying to achieve 7~7.5 psi).
A little history...
The carb, regulator and dual fuel line assy were tried and true parts from my old truck so I know this regulator is a reliable part and design. The only thing different about this set up is the gauge and pump; I previously used an in cab gauge and a Holley "blue" electric pump with a high pressure spring so it was pushing approx 18psi to the reg which then cut it down to a consistant 8psi.
As for the truck, I built it for the previous owner - original 350 swapped for a carb'd 454 using the OE fuel pump and lines with a Mallery return style regulator that ran a consistant 7~7.5psi. No trouble.
I'm stumped...
This is a 91 K5, I'm using the original tbi tank and fuel lines with a new GM replacement pump. At the motor I have a Holley 750 carb using a Barry Grant bypass return pressure regulator with a Holley 15psi pressure gauge on it. The fuel system still uses the overflow return line back to the tank.
When I first hooked up the battery and turned on the pump I couldn't control the pressure, it had a constant 13psi no matter how I adjusted the regulater. I bought a rebuild "kit" (just a diaphram and spring) and new gauge thinking one of the two was dead from sitting up for a few years.
After replacing parts I still had the same problem, a constant 13 psi (gauge close but not pegged). At this point I figured the return line was plugged - dirt dobber, trash, etc.. Today I blew air through the line and it appears to be clear. Now I can only muster 5.5psi.
I can make adjustments down in pressure but it will not go any higher (I'm trying to achieve 7~7.5 psi).A little history...
The carb, regulator and dual fuel line assy were tried and true parts from my old truck so I know this regulator is a reliable part and design. The only thing different about this set up is the gauge and pump; I previously used an in cab gauge and a Holley "blue" electric pump with a high pressure spring so it was pushing approx 18psi to the reg which then cut it down to a consistant 8psi.
As for the truck, I built it for the previous owner - original 350 swapped for a carb'd 454 using the OE fuel pump and lines with a Mallery return style regulator that ran a consistant 7~7.5psi. No trouble.
I'm stumped...
