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Thread: Flex Fuel Fuel Pump Limits and Problem

  1. #1

    Flex Fuel Fuel Pump Limits and Problem

    Quick question what is the limit on a 2012 Silverado 5.3 Flex Fuel, fuel pump. I am assuming its 250lph to keep up with E85 and good for 550-600 at the wheels. This Silverado has a Whipple Supercharger and ZR1 Injectors. I am hitting 100% DC on the injectors at 6100rpms with only 8psi and fuel pressure is dropping to 47-48psi. Knowing the injectors, I figured the fuel pump was way smaller and installed an MSD boost a pump. I now have 18 volts going into the FPCM at WOT, However I only have 10.5volts coming out of the FPCM. I have installed many MSD BAP setups on other trucks, Camaros, vets and always had great results. I know the BAP is working but I have no voltage change on the pump side of the FPCM regardless of BAP or no BAP the most I am seeing is 10.5V. I have no dtc codes but the FPCM seems to be limiting voltage way below even factory voltage limits. Any thoughts?

    Bad383TA

  2. #2
    Potential Tuner
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    Quote Originally Posted by bad383ta View Post
    Quick question what is the limit on a 2012 Silverado 5.3 Flex Fuel, fuel pump. I am assuming its 250lph to keep up with E85 and good for 550-600 at the wheels. This Silverado has a Whipple Supercharger and ZR1 Injectors. I am hitting 100% DC on the injectors at 6100rpms with only 8psi and fuel pressure is dropping to 47-48psi. Knowing the injectors, I figured the fuel pump was way smaller and installed an MSD boost a pump. I now have 18 volts going into the FPCM at WOT, However I only have 10.5volts coming out of the FPCM. I have installed many MSD BAP setups on other trucks, Camaros, vets and always had great results. I know the BAP is working but I have no voltage change on the pump side of the FPCM regardless of BAP or no BAP the most I am seeing is 10.5V. I have no dtc codes but the FPCM seems to be limiting voltage way below even factory voltage limits. Any thoughts?

    Bad383TA
    Try checking for voltage drop across the pump positive and negative terminals, anything close to zero is good anything above 1v is a bad pump.

  3. #3
    Hopefully the OP got this fixed by now, as the post is over 3 years old. But for anyone else, look at your FPCM cal, mine stock was commanding lower pressure as lb/hr went up. Logged pressure drop and thought I was out of pump, but was not. Flex fuel gen4 6.2.

  4. #4
    Quote Originally Posted by Bromeo90 View Post
    Try checking for voltage drop across the pump positive and negative terminals, anything close to zero is good anything above 1v is a bad pump.
    That is not the correct way to voltage drop test. Also, never hook a booster to the fuel control module. You will just fry it if anything.