Welcome to CPGNation.com! Log in or Sign up to interact with the CPGNation community.

1500 RPM 100% Inj. DC Spike

Discussion in 'FAST Support Forum' started by Dart67, Feb 26, 2018.

  1. Dart67

    Dart67 Member

    Sep 12, 2011
    Jessieville, Arkansas
    I have been working for the last couple of days trying to isolate the infamous 1500 RPM 100ms spike

    I will not go into the complete step by step.

    But I one by one unplugged or disconnected everything and anything that worked off of the switched side of the ignition switch and or was related to the switched leads of the XFI 2.0 ECU.

    The bottom line the LAST switched component left to isolate seems to be the problem.

    That being the F.A.S.T. Dual Sync Distributor.

    The ignition switch has been turned from OFF to Run and left on the Run position.
    This spike occurs when the ignition switch is turned from the Run to the Start position

    It does not cause the spike EVERY time but it does more often then not.

    Keep in mind. the only thing connected to the ECU at this point is the F.A.S.T. Dual Sync Distributor.

    The starter is not connected or operational at this point.

    I have attached two logs for you to look at.

    One is with everything disconnected except the Dual Sync Distributor.

    The other is with everything disconnected and the Dual Sync Distributor connected.

    If you turn off everything on the data logs off except Battery voltage, RPM and Inj. DC and watch the battery voltage in each log, you can see where I turn the ignition switch from the run to start position.

    Any suggestions on how to fix the Dual Sync Distributor ?


    Attached Files:

  2. Caprimaniac

    Caprimaniac Member

    Nov 6, 2011
    I'm note sure if there's anything to fix.
    There was a long thread 2-3 years back about his ign on spike. It is just there... I suspect ou see the same thing. Looking at Your log With soikes- did you turn the ign on and off multiple times?

    So, does Your car atsrt and run as it should? If so, you might leave the problem to rest?
  3. Dart67

    Dart67 Member

    Sep 12, 2011
    Jessieville, Arkansas
    I have read that complete thread and everything else on the forum in regards to this.

    The only time the spike occurs is when the FAST Dual Sync distributor is connected.

    Yes, the car does start and run OK.

    I bought my XFI from Rich "FastManEFI" about 13 years ago. Rich has been helping me with my tune and saw the spike in my logs. He said it is something that I should try to correct.

    Like I said above, I have gone through a thorough troubleshooting/isolation process.

    It appears as if the problem lies with the distributor. I do not know if or what type of circuit may be in the distributor. I may disassemble it later to investigate.

    I am waiting for a call from I guess second level FAST tech support tomorrow.
  4. Fastmanefi

    Fastmanefi Well-Known Member

    Jun 4, 2011
    Sonora, CA
    I would really like to fix this problem once and for all. I have another customer who engine kicks back whenever this spike occurs. It is very bothersome!
  5. Turbobitt

    Turbobitt Member

    Nov 14, 2010
    Seems like Everyone has this spike, regardless of ignition type. I do not have a dual sync distributer, or any distributer and have this spike with the factory Buick DIS and also with the XIM.

    I seem to remember the spike corresponding to the internal switching of the fuel pump to the run condition while cranking and think there could be some internal electrical noise from that. I always see the fuel pressure rise at the spike during cranking in all of my cranking data logs. And as stated doesn't happen all the time.

    Additionally, I never see any kickbacks from this spike. My 60-2 trigger wheel on the XIM have eliminated any kickback issues I was seeing from the original 3 pulse wheel and slow cranking speed leading to RPM and timing calculation errors caused by the mentioned 3 pulse wheel and slow cranking speed.
    Last edited: Feb 27, 2018

Share This Page