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EZ EFI 1.0 runs good for ~10 min then stumbles and surges and dies...

Discussion in 'FAST Support Forum' started by Pandora, Sep 3, 2018.

  1. Pandora

    Pandora New Member

    Joined:
    Jul 16, 2016
    Short back story. '78 El Camino, 30-over 350 with Edelbrock Performer RPM heads, cam, Airgap intake. Switched from carb to EZ EFI in ~2012, ran great 'til 2016. It sat for some time. My son told me he drove it weekly/semi-weekly and put fresh gas in "all the time". Then it wouldn't start. So I packed it up and brought it home and started digging into the issue. I could keep the motor running if I dribbled gas down the TB but it died if I stopped. So I started looking at the fuel system. Gas smelled old, really old. I took the injectors out and they were plugged with solid fuel - yes you read that right, solid. Clearly it wasn't being operated as often as indicated. Found 1/2" of water in the tank too and lots of rust. Got the injectors cleaned and reconditioned, new fuel lines, new tank, new pump (Racetronix), new filters (pre and post pump).
    So now it starts and idles nicely while it warms up then after about 8 minutes or so after it gets to 180F is starts to stumble and surge. On the hand held the AFR swings quickly above and below the target and the idle goes all over the place at the same time until it finally dies - this is about a 5 min process.
    From a cold start I can let it warm for a few minutes, drive it for a a few minutes, cruises nicely, WOT no problem, then the surging and sagging starts. No error codes on the hand held, and solid blue light as well. I've rerouted the wiring harness completely away from the distributor as well as switched to shielded cables for the wires that do go to the distributor and MSD 6A box, still no luck.
    I can let it all cool to ambient and start the process over again and get the same results.
    This is where data logging of the various CPU values would be really nice.

    Any ideas?

    Thanks,

    Scott
     
  2. Pandora

    Pandora New Member

    Joined:
    Jul 16, 2016
    AA, you are correct on the intake - Edelbrock RPM Airgap intake - dual plane, BUT with a 1" cut out of the center divider - not changing it.
    MSD 6A box runs hot (really hot), but passes their function test both when cold and hot. Replaced with a new MSD 6EFI runs cool, but 12-15 minutes later same issue with stumble and surge and die.
    Checked the coil and both resistance values were within spec both cold and hot just after shutdown.
    It had run on the really old gas to empty the tank. thought O2 sensor may have been plugged up so a new one went in and no change.
    Found the MAP sensor loose - the grommet had shrunk in the middle. Replaced with new unit from FAST, no improvement
    Completely rerouted all wiring to opposite side, despite solid blue light, and no improvement.
    Took a closer look at the coil and found a melted section on one side and a crack in the casing on the under side [​IMG]
    New coil did the trick. Now to let the computer learn and update...

    Thanks for the help!

    Scott
     
  3. Pandora

    Pandora New Member

    Joined:
    Jul 16, 2016
    Runs OK, but just OK. Will throw an O2 sensor code every once in a while causing a stumble. Turn off, back on and OK for a while. Fan relay does not activate fan and does not quite give full ground at selected temp, just 1.14 kOhms from FAST ECU. Relay works fine when low current side connected directly to ground. Could this be part of the rest of the issues I'm seeing, despite main power and ground direct connection to battery with gold plated terminals?
     
  4. gremlinmt

    gremlinmt Member

    Joined:
    Mar 13, 2013
    Agreed. Going to single plane is shockingly better. I noticed no loss in torque. However, I did 5 years with my dual plane trying to make it work. I never lost a MAP sensor.
     
  5. Pandora

    Pandora New Member

    Joined:
    Jul 16, 2016
    From my post back in Dec.. "Will throw an O2 sensor code every once in a while causing a stumble. " The weather and my schedule finally aligned and I got to do some playing and watching. What I noticed is that, from cold, it starts fine, idles down nicely as it warms up but just after the Fan On temperature set point (180), the stumble happens. BTW, there are no fans connected to the ECU; not a solid enough ground to trip the relay when called for.
    So I happened to be watching the hand held right next to the ECU and the solid blue light went out for a fraction of a second, it stumbled, the blue light came back on and it ran, but rough and looking for a stable idle. The hand held showed lost comm and upon restart and going to second page the IAC level was 80+/- rather than the 18-20 is sits at normally at idle, and an O2 error code. Turn engine off, back on, and IAC is back to 18 at idle and O2 fine now. Within a minute or two, the blue light goes out for a fraction of a sec, stumble, runs rough. restart the hand held and IAC is 99. Let it cool completely (over night) restart nicely like before, while warming up I raised the Fan On to 200F and sitting at warm idle the engine runs at 175-178 with 2 electric fans going. It idled for over an hour without a hiccup, I played with throttle position, running at 2500-3000 for several minutes at a time then back to idle. Then I reset the Fan On to 175 and pulled the fuse on one of the fans. Just shortly after the engine hit 180 the blue light flashed again and the above issues seen. I raised the Fan On back to 200, but I guess whatever is going on stuck, because it then stumbled again after about 10 minutes of idling at 180. Let it cool over night again and it starts and runs fine as long as it doesn't go over the Fan On temp.
    This has to be more than a single plane/dual plane intake issue.
     
  6. Pandora

    Pandora New Member

    Joined:
    Jul 16, 2016
  7. Pandora

    Pandora New Member

    Joined:
    Jul 16, 2016
    Ignition OFF:
    Battery, 13.35V

    Ignition ON:
    Battery, 12.45V (2 fans running)
    Pink wire @ tie in point - 3 feet from ECU, 12.35V
    ECU, Page 3 Bat 12.0V

    Engine Running:
    Battery, 13.25V
    Battery + to Alternator chassis, 14.25V
    Pink wire @ tie in point, 14.25V
    ECU, Page 3 Bat 12.2V Cold 11.9V Hot

    So given that at when the Fan ON temp hits, I'm only seeing 1.14 kOhms from FAST ECU relay output, not full ground, could there be an issue inside the ECU?
     
  8. Pandora

    Pandora New Member

    Joined:
    Jul 16, 2016
    Not sure what happened to member A A or his posts, but I cleaned up all the electrical connections - sand paper, acetone, new bolts, tap chased threads, Deoxit-5, etc. and some improvement in voltage seen at Hand Held unit. Ran (idled) over an hour today with an O2 error at about 45 min. Turned off, back on, error gone - didn't have to clear it (?!?). ECU holding steady at 13.0V with no fans on, battery at 13.5V and ECU at 12.6V with 2 fans on, battery @ 12.72V. Short road trip tomorrow.
     

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