Page 2 of 2 FirstFirst 12
Results 16 to 21 of 21

Thread: 01 4.3 won't start...fuel issue I believe, need some help!

  1. #16
    Registered User
    Join Date
    Dec 2004
    Location
    Texas
    Posts
    11
    Ok, it looked redneck, but from a physics standpoint, it was by the book! I put up a 10 foot ladder next to the Jeep and ran a line from an upside down two gallon vented gas can at the top to the input of the filter and rechecked all of my pressures again (at the schrader, dead headed in front of the fuel filter). 71 at the filter and 48 under the hood. (This was done to make sure the pump was getting all the fluid it needed and that there wasn't a plumbing/siphon issue with the pump and tank relationship). Since I have a new pressure regulator, and upon the advice from Jon at FuelInjectorConnection.com, I believe I have leaky injectors that are not allowing the correct pressure to be built up. This also seems to be a strong possibility since my pressure at the schrader immediately goes to 0 when I shut off my fuel pump or turn the key off. So, I ordered a new unit and will get that in as soon as it arrives. Hopefully that will be the solution.

    As a side note, I am in no way affiliated with fuelinjectorconnection.com, other than that I have ordered from them before and they have GREAT prices ($200 for a full set of Bosch III's and all new gaskets for my 89 TPI Vette), as well as top notch customer service. Just something I picked up from over on the Vette forums and thought I would pass along.

    Updates to follow as they become available...many thanks for everyone's input!!

  2. #17
    Zombie Killer 6SpeedBlazer's Avatar
    Join Date
    May 2004
    Location
    Lake St. Louis
    Posts
    6,594
    Quote Originally Posted by shiner2001 View Post
    The in tank pump for the Jeep only puts up 31 psi with the vacuum line attached at the factory Jeep pressure regulator and 39 with it disconnected. This wouldn't satisfy the requirements of the 4.3 for pressure, correct? Right now I am getting 48 at the schrader when running just the pump in the "on" position when jumper cables are attached to another running vehicle and can't get it to start.

    I am just about to go test with an elevated, external, gravity feed fuel tank connected to the current frame mounted fuel pump and see if my pump/tank orientation might be causing some issues. What gets me about this whole setup is that it ran great for years as it is now. I am wondering if the fuel pump has finally just declined to the point that it can't keep up.
    the fuel pump has little to do with creating pressure. you need a pump that CAN SUPPLY THE VOLUME to create the pressure. the pressure regulator is what dictates pressure.

    the mpfi jeep pump will work fine.

  3. #18
    Registered User
    Join Date
    Dec 2004
    Location
    Texas
    Posts
    11
    Quote Originally Posted by 6SpeedBlazer View Post
    the fuel pump has little to do with creating pressure. you need a pump that CAN SUPPLY THE VOLUME to create the pressure. the pressure regulator is what dictates pressure.

    the mpfi jeep pump will work fine.
    I'm gonna have to disagree with you on that one. The pump is the only part of that system that creates pressure. If it's not enough from the pump, the regulator can't "make up for it" at the engine. I'm afraid that a pump that puts out only half of what is required by the injectors and ECM just would not cut it. Hence the reason I didn't keep the Jeep set up from the time I installed the 4.3.

  4. #19
    Zombie Killer 6SpeedBlazer's Avatar
    Join Date
    May 2004
    Location
    Lake St. Louis
    Posts
    6,594
    Quote Originally Posted by shiner2001 View Post
    I'm gonna have to disagree with you on that one. The pump is the only part of that system that creates pressure. If it's not enough from the pump, the regulator can't "make up for it" at the engine. I'm afraid that a pump that puts out only half of what is required by the injectors and ECM just would not cut it. Hence the reason I didn't keep the Jeep set up from the time I installed the 4.3.
    you can disagree all you want, but i am still correct.

    if you have a pump that has a disconnected outlet the system PSI is going to be next to zero.

    in order for the pressure to raise you need to "pinch" the system aka install a regulator.

    think about it this way. how much pressure does a garden hose have when there is no nozzle on the end? how much pressure does the garden hose have when there is a 1/4" nozzle on the end? a fuel system works in the same way. the fuel pump has to be able to provide the volume of fuel that the system needs in order for the regulator to create the pressure. without a regulator the system would have almost zero psi.

  5. #20
    Registered User
    Join Date
    Jan 2010
    Location
    Maryland
    Posts
    326
    The pump is volume and volume only. Restriction is where PSI come in to play. The more the restriction the higer the PSI and vice-versa. The pump is always going to pump the same volume no matter what. Thats why we do volume tests on pumps. Say its rated at 60 gph thats one gallon in one minute. 1 qt in 15 seconds if it flows less it fails becauses its not flowing proper volume which is directly related to PSI. If its not pumping the right volume PSI is going to be low.

  6. #21
    Registered User
    Join Date
    Dec 2004
    Location
    Texas
    Posts
    11
    Replaced the injectors and all is well. Pump was fine.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •