1. Welcome to Tacoma World!

    You are currently viewing as a guest! To get full-access, you need to register for a FREE account.

    As a registered member, you’ll be able to:
    • Participate in all Tacoma discussion topics
    • Communicate privately with other Tacoma owners from around the world
    • Post your own photos in our Members Gallery
    • Access all special features of the site

Need clarification of fuel pressure 3RZ

Discussion in '1st Gen. Tacomas (1995-2004)' started by F.I.LetsGoFishing, Mar 13, 2021.

  1. Mar 13, 2021 at 6:22 PM
    #1
    F.I.LetsGoFishing

    F.I.LetsGoFishing [OP] Well-Known Member

    Joined:
    Nov 9, 2011
    Member:
    #66729
    Messages:
    162
    Gender:
    Male
    Vehicle:
    95.5 4wd 3rz mt
    Neglected Original
    My 95 taco with 2.7 3RZ has a no start issue and reading through the searched topics I am a little confused. I started with no start when parked at an angle now no start at all. I know I have spark to #1 so next was fuel, Reading manual shows I have to check pressure at fuel rail inlet which is after filter so I changed filter being that I have 260k miles. While reinstalling I went ahead and installed a rented fuel pressure gauge at the bango connection at fuel rail (rear drivers side) to check fuel pressure. going by the book I think was supposed to have pressure when key went to ON position, but do not. If I turn the engine over, I recieve pressure while it tries to crank. when I let go of key the pressure immediately starts dropping. sometimes holding at 21# sometimes not. my first question is
    Should I have pressure build simply when in the on position?
    second question
    once the pressure starts while cranking, considering I have some spark, shouldn't I get some form of start, even if rough?
     
  2. Mar 13, 2021 at 10:18 PM
    #2
    TnShooter

    TnShooter The TacomaWorld Stray

    Joined:
    Sep 2, 2010
    Member:
    #42625
    Messages:
    21,222
    Gender:
    Male
    First Name:
    Deogee
    Vehicle:
    07' TRD Off-Road, Auto
    STOCK
    I can’t remember for sure on those years.
    But I think the engine needs to be cranking for the c/open relay to close.
    C/open relay is what powers the fuel pump. So you would need to have the truck cranking to get fuel pressure.

    I may be wrong. I’d wait to see what the guys that know for sure say.
     
  3. Mar 14, 2021 at 1:17 AM
    #3
    Wyoming09

    Wyoming09 Well-Known Member

    Joined:
    Apr 24, 2015
    Member:
    #153833
    Messages:
    14,277
    Gender:
    Male
    New Tripoli Pa
    Vehicle:
    2000 Work truck 5 speed 4x4 3.4
    Super Springs
    Correct fuel pressure when cranking or running . Not like the eighties that primed with the ignition on one of those things I guess they figured was not needed.

    Remember just because you have fuel pressure the injectors might not be firing.Might be your failure to start.
     
    DrZ and TnShooter like this.
  4. Mar 14, 2021 at 10:42 AM
    #4
    F.I.LetsGoFishing

    F.I.LetsGoFishing [OP] Well-Known Member

    Joined:
    Nov 9, 2011
    Member:
    #66729
    Messages:
    162
    Gender:
    Male
    Vehicle:
    95.5 4wd 3rz mt
    Neglected Original
    So, Today it started with the aid of starting fluid through the PCV port. Runs rough at first then settles to what I consider a fair idle. I let it run until it reached normal temp. Fuel pressure while running held a constant 46#.
    Ran an OBD scan and and left hooked up for 15 minutes received code PO 115 coolant temp low. cleared code
    let truck sit for 2 hours and fuel pressure remained at 36#
    tried to restart but again had to use starting fluid.
    Code po115 returned.
     
  5. Mar 14, 2021 at 1:10 PM
    #5
    Allex95

    Allex95 Well-Known Member

    Joined:
    Apr 6, 2020
    Member:
    #324011
    Messages:
    1,380
    Gender:
    Male
    First Name:
    allex
    Vehicle:
    96 Tacoma 4x4 2.7l 4 cylinder
    That’s a coolant sensor on the back of the head
     
  6. Mar 14, 2021 at 1:12 PM
    #6
    Wyoming09

    Wyoming09 Well-Known Member

    Joined:
    Apr 24, 2015
    Member:
    #153833
    Messages:
    14,277
    Gender:
    Male
    New Tripoli Pa
    Vehicle:
    2000 Work truck 5 speed 4x4 3.4
    Super Springs
    If you can`t read real time coolant temps read the resistance across the coolant temp sensor .

    Your not low on coolant by chance ?

    That can act like a bad sensor.

    Anything get bumped or damaged hooking up the fuel pressure gauge?
     
  7. Mar 14, 2021 at 3:33 PM
    #7
    F.I.LetsGoFishing

    F.I.LetsGoFishing [OP] Well-Known Member

    Joined:
    Nov 9, 2011
    Member:
    #66729
    Messages:
    162
    Gender:
    Male
    Vehicle:
    95.5 4wd 3rz mt
    Neglected Original
    not finding any sensors on the back of the head. have any links showing on the 3rz in 95?
     
  8. Mar 14, 2021 at 4:17 PM
    #8
    Allex95

    Allex95 Well-Known Member

    Joined:
    Apr 6, 2020
    Member:
    #324011
    Messages:
    1,380
    Gender:
    Male
    First Name:
    allex
    Vehicle:
    96 Tacoma 4x4 2.7l 4 cylinder
    C2934B42-E2EF-444A-A7F8-C9EE30D55B69.jpg
    this sensor
     
  9. Mar 14, 2021 at 4:36 PM
    #9
    F.I.LetsGoFishing

    F.I.LetsGoFishing [OP] Well-Known Member

    Joined:
    Nov 9, 2011
    Member:
    #66729
    Messages:
    162
    Gender:
    Male
    Vehicle:
    95.5 4wd 3rz mt
    Neglected Original
    found it. now got to find one and see what fresh new hell yoda got in store for me this time. Fuel filter was lots of fun
     
  10. Mar 14, 2021 at 8:22 PM
    #10
    Wyoming09

    Wyoming09 Well-Known Member

    Joined:
    Apr 24, 2015
    Member:
    #153833
    Messages:
    14,277
    Gender:
    Male
    New Tripoli Pa
    Vehicle:
    2000 Work truck 5 speed 4x4 3.4
    Super Springs
    Remember the sensor is only one part of the complete circuit.
     
  11. Mar 14, 2021 at 8:24 PM
    #11
    Allex95

    Allex95 Well-Known Member

    Joined:
    Apr 6, 2020
    Member:
    #324011
    Messages:
    1,380
    Gender:
    Male
    First Name:
    allex
    Vehicle:
    96 Tacoma 4x4 2.7l 4 cylinder
    What does thst mean? I don’t have the problem the op is having but I have a cold start low idle which I believe is the sensor or wiring to that sensor causing it
     
  12. Mar 14, 2021 at 8:32 PM
    #12
    Wyoming09

    Wyoming09 Well-Known Member

    Joined:
    Apr 24, 2015
    Member:
    #153833
    Messages:
    14,277
    Gender:
    Male
    New Tripoli Pa
    Vehicle:
    2000 Work truck 5 speed 4x4 3.4
    Super Springs
    With any Code you have the sensor the wiring harness and The Ecm.

    So many see a code run out buy a new sensor and get upset when it does not fix the problem.

    The sad part most sensors can be tested so easy.
     
    Dm93 likes this.
  13. Mar 14, 2021 at 8:48 PM
    #13
    DrZ

    DrZ Well-Known Member

    Joined:
    Dec 14, 2014
    Member:
    #144262
    Messages:
    1,459
    Gender:
    Male
    Mesa, AZ
    Vehicle:
    96 2.4L 5-speed
    With P0115 the computer goes into fail-safe mode and assumes the coolant temperature is near normal operating temperature 80°C (176°F). This is why it is so hard to start when cold, but it will run about normal once it is actually warm, because the actual temperature is about what it assumes.

    Yes, test the sensor before replacing. No need to replace a perfectly good Toyota sensor with a cheaper aftermarket. Just pull out a multimeter and check the resistance of the sensor. The computer is just detecting a short or open circuit. It could be the sensor OR it could be a broken wire.
     
    Wyoming09 likes this.
  14. Mar 14, 2021 at 8:54 PM
    #14
    Allex95

    Allex95 Well-Known Member

    Joined:
    Apr 6, 2020
    Member:
    #324011
    Messages:
    1,380
    Gender:
    Male
    First Name:
    allex
    Vehicle:
    96 Tacoma 4x4 2.7l 4 cylinder
    I heard that if the degrees is negative degrees it means open circuit?
     
  15. Mar 15, 2021 at 2:15 AM
    #15
    DrZ

    DrZ Well-Known Member

    Joined:
    Dec 14, 2014
    Member:
    #144262
    Messages:
    1,459
    Gender:
    Male
    Mesa, AZ
    Vehicle:
    96 2.4L 5-speed
    Open circuit mean the computer detects infinite resistance as if you unplugged the sensor, or there is a broken wire, or the sensor fell apart internally. At cold temperatures the sensor resistance will increase, but it will still have some resistance less than infinity, so it won't throw a P0115.
     
    Wyoming09 likes this.
  16. Mar 15, 2021 at 1:46 PM
    #16
    F.I.LetsGoFishing

    F.I.LetsGoFishing [OP] Well-Known Member

    Joined:
    Nov 9, 2011
    Member:
    #66729
    Messages:
    162
    Gender:
    Male
    Vehicle:
    95.5 4wd 3rz mt
    Neglected Original
    I agree with check first as long as I can do so without pulling. If I do replace it will be with parts from Toyota as I have become a believer that there is a reason I still have so much original after 260K. I will likely regret using aftermarket on the filter after the experience of replacing. made that mistake with clutch master cylinder and have to replace that lifetime piece of garbage every 2 years.
    Now if I can just keep it running for 1 more year so I can attack replacing the nonworking ac and the oil leaks. This is to become strictly my hunting/fishing truck.
     
  17. Mar 15, 2021 at 3:39 PM
    #17
    F.I.LetsGoFishing

    F.I.LetsGoFishing [OP] Well-Known Member

    Joined:
    Nov 9, 2011
    Member:
    #66729
    Messages:
    162
    Gender:
    Male
    Vehicle:
    95.5 4wd 3rz mt
    Neglected Original
    guess replacement either way. went to pull the lead and came up with this still in the connector.20210315_182629[1].jpg
     
  18. Mar 15, 2021 at 3:44 PM
    #18
    Glamisman

    Glamisman Well-Known Member

    Joined:
    Oct 22, 2016
    Member:
    #200436
    Messages:
    4,940
    Gender:
    Male
    You found a hedgehog in your motor? he he he...
     
  19. Mar 16, 2021 at 3:38 AM
    #19
    Wyoming09

    Wyoming09 Well-Known Member

    Joined:
    Apr 24, 2015
    Member:
    #153833
    Messages:
    14,277
    Gender:
    Male
    New Tripoli Pa
    Vehicle:
    2000 Work truck 5 speed 4x4 3.4
    Super Springs
    It seems that may be the cause of your code .

    Open circuit or resistance so high the ECM just said this is broke!
     

Products Discussed in

To Top