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o2 sensor code, no start

Discussion in 'FAST Support Forum' started by waybad1, Oct 21, 2017.

  1. waybad1

    waybad1 New Member

    Joined:
    Jan 22, 2012
    Well I have had my ez efi 1.0 system for years and love it. No real issues until today. I was driving
    and my truck did a loud backfire and shut off. Not good, no steering in a truck with 42" tires. It cranks
    over but will not start. It throws an o2 code right away and the light flashes on the module. The truck
    sat for appr. 2 months and there is a bad fuel smell from the throttle body and header when I removed
    the O2 for inspection. I have been driving it for a couple of days now after repairs and it has run
    excellent. Any help is appreciated.
     
  2. waybad1

    waybad1 New Member

    Joined:
    Jan 22, 2012
    Also no cranking rpm when turning over. Thanks
     
  3. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    What repairs? If it runs excellent now, after repairs, what kind of help is needed?
     
  4. waybad1

    waybad1 New Member

    Joined:
    Jan 22, 2012
    I actually just did some oil leak repairs. Nothing related to the efi system. It was sitting for a couple of months and I drove it at least 50 miles before this happened
    so I dont believe the fuel is bad even though you get that smell of bad fuel from the throttle body. The fuel in
    the cell smells good. I was accelerating from a stop when it backfired loud, sounded like out the exhaust, but I cranked
    it over with the air filter off and saw it backfire through the throttle body. It sets an o2 sensor code on crank every time I try to start it.
    No cranking rpms. It just died so suddenly, that just doesn't sound like bad fuel or an o2 unless the pcm cuts off everything when
    it sees an o2 code
     
  5. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    Check the MAP sensor, and the power during start to the ECU and the handheld. Also check for any bad ground connections with an Ohmmeter.
     
  6. waybad1

    waybad1 New Member

    Joined:
    Jan 22, 2012
    The light on the ecu flashes when cranking. I watch the handheld when cranking and see it set the se light so it has power.
    I can check all the grounds, but dont know to check the MAP. Is that checked with the handheld?
     
  7. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    On the power, you could be getting low voltage during crank, or an intermittent problem there. Voltage should stay above 12 cranking, and 13.4 running. Check the battery has at least 12.5 volts resting. To check the MAP, you key on, but do not start the engine. Depending on your altitude, the handheld MAP reading should be close to 100.

    If these things check good, look for an ignition fault - check inside the distributor, the coil, and all the ignition box wiring for good contacts. Beyond that, you could have a failing ignition box or coil. Usually, there is just some corrosion somewhere in the wiring when a vehicle has a problem after sitting up.
     
    Last edited: Oct 22, 2017
  8. waybad1

    waybad1 New Member

    Joined:
    Jan 22, 2012
    Ok, MAP reads 101. Battery 12.87 volts with my fluke and load tester (just fully charged) Passes load test.
    Voltage on handheld shows 11.5 volts static and drops to 8.8 volts when cranking. Still no start of course
     
  9. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    You've found the root of the problem. Your battery capacity has dropped too low for one. The system requires 11+ volts during cranking. I'll bet you didn't let the battery rest 24 hours and then check voltage after charging it - it should remain at or above 12.7 after 24 hours of no use, if charged to capacity. If the battery is strong, it shouldn't drop to 8.8 during cranking. Sounds like you have a sulfated battery from sitting up. You might try de-sulfating the battery using a charger with this capability. Be sure to check the charging system once you get the engine running.

    The handheld should also be showing the same voltage as you found at the battery terminals, or very close to it. Be sure to check your key switch voltages. You could have a bad/corroded switch.
     
  10. waybad1

    waybad1 New Member

    Joined:
    Jan 22, 2012
    I fixed a couple suspect grounds. Everything I touched positive wise was close to battery voltage. At the starter, the 2 positive terminals on the firewall
    every fuse static and key on. I wanted to check power at the module itself but didn't want to poke into the wire. I tried another battery out of
    one of my other vehicles and it was the same 12.7 volts at the battery and 11.5 at the handheld. The fast and Msd module are both wired directly
    to the battery positive and ground.
     
  11. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    Check the voltage on the wire feeding the handheld with power. The handheld should be showing a reading very close to the battery terminal reading. You could have a bad ignition switch. Connect the handheld and the ECU pink ignition power wire directly to the battery 12+ terminal for testing.

    The FAST ECU and MSD ignition box should not be wired to the same terminals. The ignition box will send interference into the ECU if they are connected to the same terminals. Ground the MSD to the engine and keep the MSD ground there.

    Then, do a Wizard reset and input all your user data. If the plugs still aren't firing, check the MSD box and coil out.

    If the MSD box and coil are good, contact FAST and send the ECU and handheld in for testing and possible needed repair.
     
  12. waybad1

    waybad1 New Member

    Joined:
    Jan 22, 2012
    I still have 12.7 volts at the battery after sitting overnite. I did not load test it this morning.
    Battery voltage is 12.3 to 12.4 at the handheld connection, but the handheld is steady at 11.5 static.
    Thats right about where its been since it died. Its hard to continue checking cranking voltage due to it
    backfiring out of the throttle body. It is very aggressive. I checked spark from the coil early on and it
    was strong.
     
  13. Fastnofast

    Fastnofast Member

    Joined:
    May 16, 2017
    backfire is a faulty distributor or wrong initial advance. As AA said did you check those parts ?
     
  14. waybad1

    waybad1 New Member

    Joined:
    Jan 22, 2012
    I've had the Fast installed for several years now and have never had a backfire until the other day when it stalled.
    I've got it dialed in pretty well, no hesitation on accell or at WOT, great idle when warm. Runs strong, Just backfired and died
    right away. I had not done any recent repairs/changes to anything with the fuel or ignition, just fixed and oil leak at the back
    of the block. It at the time of stall had an o2 code that set everytime I cranked it over and it was backfiring. This happended
    so suddenly I think it has to be a hard part fault
     
  15. waybad1

    waybad1 New Member

    Joined:
    Jan 22, 2012
    So I checked the switched power to the pink wire from behind the fuse box up to where the pink
    wire goes into the ECU 9.8 to 10.00 volts there.
    I am also wiring the MSD ground to the engine
     
  16. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    That pink ignition wire to the ECU has to have +12 volts. This is also the wire that tells the handheld what voltage to display.

    Sounds like you had it dialed in just fine before, but those settings could have changed after this problem. The MSD wired to the same battery terminals as the ECU probably caused a severe interference event (cumulative) in the ECU - ignition box interference can cause damage to the ECU - and at the least will scramble the ECU user data. If you were the original purchaser and have damage, FAST will do the repair free, and update the software to the latest version while they're at it. Still, the low voltage at the ECU pink ignition wire could be all or most of what is keeping the engine from starting. Temporarily connect it directly to the battery +12 volt terminal, re-set the ECU, and see if the engine runs then. If it doesn't, you will have to RMA the ECU and handheld.
     
  17. waybad1

    waybad1 New Member

    Joined:
    Jan 22, 2012
    12 volts to the pink wire is my next step. I will let you know. Thanks. I am the original purchaser.
     
  18. waybad1

    waybad1 New Member

    Joined:
    Jan 22, 2012
    Ok, I connected the pink wire to a 12 volt source. Reset the ECU and tried to start the vehicle
    backfires right away. The voltage readings in the handheld stayed the same as before. I cant get that above
    11.5 volts even though I know I have 12 volts everywhere else.
    I now feel like it is the ECU. I see 12 + volts going in, just low voltage readings
    static and cranking from the handheld
     
  19. waybad1

    waybad1 New Member

    Joined:
    Jan 22, 2012
    Also is it both positive and negative that have to be separate in the MSD and Fast ECU? If so can I power one up off the top and
    side terminals on my battery. The MSD ground is already going to the block. Thanks
     
  20. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    You can leave the ECU and MSD +12 volt power wires connected at the same battery terminal. You solved that MSD interference problem when you changed the ground connection to the engine block.

    Yes, unfortunately, you will need to call the tech line for an RMA of the ECU and handheld. FAST Tech may want a few more checks, but I'm satisfied you need a RMA due to the low voltage displayed at the handheld.

    In any case, be sure to check the engine didn't jump time when the problem first happened.
     
    Last edited: Oct 25, 2017

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