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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. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    The first thing to check is the ignition box and coil. One or the other could be breaking down. If the intake is a dual plane, as I suspect, the MAP sensor is also likely bad. Short story, dual plane intakes and TBI don't play well together. Changing to a single plane intake offers a lot of improvement - and increased MAP sensor life when it is mounted directly to the throttle body.
     
  3. 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
     
  4. 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?
     
  5. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    The dual plane intake. They not only cause short MAP sensor life, they also don't feed equal charges to the cylinders using TBI. The relay is only affecting the fan. The sooner you toss the dual plane for a single plane, the sooner you will see engine improvement.
     
  6. 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.
     
  7. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    So many have had early MAP sensor failure, FAST has even taken to adding a second hole to the 2.0 MAP sensor passage in an effort to drain fuel away from the sensor. Apparently, they are doing this with all new 2.0 throttle bodies and add the change free of charge to older throttle bodies. I'm not sure if the change applies to 1.0 throttle bodies.

    If fuel reversion in the intake doesn't get the sensor itself, it gets to the sensor gasket to cause problems.
     

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