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Thread: Commander 950 just stops working

  1. #1
    andy2175m4@verizon.net Guest

    Default Commander 950 just stops working

    I have a commander 950 ECU and on several occasions it just stopped sending pulses to the injectors, this lasted for days or weeks at times, I verified that the pulses were not there with an oscilloscope, when it's working you can clearly see the 12v square pulses, when it's not working, nothing is there, and of course the car won't start.

    I was told by several guys that it sounded like there was no Tach pulse (ie ignition) getting to the ECU, which will prevent it from firing the injectors.

    On these occasions the laptop and 950 ECU are communicating just fine, it appears to be working fine from the laptop, but NO injector pulses.

    I used an oscilloscope with a 10:1 voltage divider probe to verify that I have the 300 volt ignition pulses coming off the coil, so I know the Commander 950 is getting a tach pulse from the engine,

    I also used an ohm meter to check the wiring harness and to verify that the tach pulse was getting thru the harness to the multi pin connector. That checked out ok.

    I send the ECU back to Holley in Kentucky and they bench tested it, per therir std procdure, and the said it was OK, but it is still not working for me.

    I have gone thru the car and checked everything I could think of, have I missed something ?

    Please reply with any and all suggestions for troubleshooting.

    thanks

    Andy

    63 Ford Thunderbird
    82 Ferrari 308

  2. #2
    Join Date
    Dec 2009
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    22,725

    Default

    Does the ECU prime the fuel pump for five seconds at key-on, during this no start condition?
    Is the "Fuel Pump On" indicator highlighted red (look on Fuel Map), when cranking but no start?
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  3. #3
    andy2175m4@verizon.net Guest

    Default

    Quote Originally Posted by Danny Cabral View Post
    Does the ECU prime the fuel pump for five seconds at key-on, during this no start condition?
    Is the "Fuel Pump On" indicator highlighted red (look on Fuel Map), when cranking but no start?

    Yes, the fuel pump prime works, and I do see a fuel pump on indicator on the fuel map, but still no injector pulses.

  4. #4
    krademacher Guest

    Default I'm interested in this answer too

    roughly the same situation. Got an LS1 with the Edelbrock carb intake and controller. The dash tach in my 1981 Trans Am is reading an RPM signal when I crank, the fuel pump comes on, the ECU reads "Pump On," plus I've tested for spark and made sure ground is solid. I've set the ECU so that it thinks there is a coil ignition (signal from coil negative terminal). All good. Still, no gas from injectors.

  5. #5
    Tom K Guest

    Default

    Quote Originally Posted by andy2175m4@verizon.net View Post
    Yes, the fuel pump prime works, and I do see a fuel pump on indicator on the fuel map, but still no injector pulses.
    Do you have 12VDC on the red wire at the injector harness during key on prime and during crank?

    Thank's
    Tom

  6. #6
    andy2175m4@verizon.net Guest

    Default

    Update to my story:

    I got suspicous of the "coil input" circuit in the ECU, and decided to try the ECU on the bench with a TFI distributor, this unit sends a 12 volt square wave to the ECU for RPM input, instead of the 200 volt coil pulse. The ECU immediately started firing the injectors.

    I then retrofitted the TFI distributor to my engine ( An old V8 Ferrari engine, no small task in itself) and the engine immediately started and ran. I have not had the "no pulses" problem since, I have had some other issues, but at least I think the "no pulses" problem is fixed.

    I have used this ECU on 2 cars, and both had distributors that were different from a pure, old fashioned, points/condensor/coil system and hence the Commander ECU did not seem to recognize the rpm signal from the coil. No matter, I wanted to update the antiquated Ferrari ignition anyway, the TFI does seem to work better, although the installation is a home made kudge and will require some care and feeding to perfect.

    Andy

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