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Thread: Holley Commander 950

  1. #1

    Default Holley Commander 950

    Hi. Installed this several years ago in a '71 DeTomaso Pantera. Has 4 port MPFI throttle body, 36 lb/hr injectors, MSD locked advance distributor, MSD 6 box.

    Car ran nice for some years, but owner started to complain about starting problems. He could easily start when cold, but when hot engine, lets say filling fuel, trying to start again, he sometimes couldn't start. Waiting 30 minutes, easy to start. We tried different after-start enrichment, but since this was a not consistent problem, we thought often we had cured it just to have a phone call later telling us wrong. We had the car back several times with same problem.

    We later discovered that the injectors don't open when this happens, but it get ignition spark. Was advised to run spark pickup
    with GM TPI ignition module, same problem. Also did convert an old points Cleveland distributor with a "platform" from a
    GM TPI small diameter distributor and pickup system. Much stronger signal, but still no injection when engine is hot.

    Any help would be appreciated. Thank you, Tjohei

  2. #2
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    Quote Originally Posted by tjohei View Post
    Car ran nice for some years, but owner started to complain about starting problems. He could easily start when cold, but when hot engine, lets say filling fuel, trying to start again, he sometimes couldn't start. Waiting 30 minutes, easy to start. We tried different after-start enrichment, but since this was a not consistent problem, we thought often we had cured it just to have a phone call later telling us wrong. We had the car back several times with same problem.
    If the engine doesn't even start, adjusting the After Start Enrichment won't help. If the engine starts, then immediately stalls afterwards, then maybe tune the After Start Enrichment, Coolant Temperature Enrichment or Main Fuel Map. If the engine cranks & cranks, but can't start, maybe tune the Cranking Pulse Width (mSec) at that temperature.
    http://documents.holley.com/techlibrary_r10149-7.pdf (C950 Tuning Manual - Figure 8, Page 29)

    We later discovered that the injectors don't open when this happens, but it get ignition spark. Was advised to run spark pickup
    with GM TPI ignition module, same problem. Also did convert an old points Cleveland distributor with a "platform" from a
    GM TPI small diameter distributor and pickup system. Much stronger signal, but still no injection when engine is hot.
    When cranking to start, is the "Fuel Pump On" indicator highlighted red (Fuel & Spark Map)?
    Does the ECU prime the fuel pump for five seconds at key-on, during this no start condition?
    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

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    Hi. The fuel pump is "on" and runs while cranking, when the problem is there. Fuel pump comes on when ignition is on for 4 seconds something. We've made it start by spraying gasoline directly into the air filter, and it then runs stable.

    Thank you, Tjohei

  4. #4
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    Quote Originally Posted by tjohei View Post
    Hi. The fuel pump is "on" and runs while cranking, when the problem is there.
    Good, that means the C950 ECU is receiving the RPM signal.

    Fuel pump comes on when ignition is on for 4 seconds something.
    Good, that means the initial fuel pump prime is working properly.

    We've made it start by spraying gasoline directly into the air filter, and it then runs stable.
    At this point, you'll have to determine why the fuel injectors don't spray fuel during this occurrence.
    I'd check the fuel injector wiring next. The fuel injectors are +12V powered by the fuel pump relay (switched/keyed,
    five second fuel pump prime & engine cranking/running), and the ECU pulses the ground side. Which is not happening?
    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.

  5. #5

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    I had this issue a few years ago, and it was the TPS arm sticking and putting the ECU in clear flood mode.
    Once the engine cooled off, the arm would release and go back. A high TPS while cranking shuts off the injectors.

  6. #6
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    Quote Originally Posted by DaveM View Post
    A high TPS while cranking shuts off the injectors.
    That would be a big problem, since the "Clear Flood TPS Position" is usually around 200 (not just off idle).
    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.

  7. #7

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    The arm on the TPS was rubbing slightly on the throttle body. When it was hot, it would stick at WOT, and hang there until it cooled off some. Ground a little bit off of the arm, and it's been good since.


  8. #8
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    Quote Originally Posted by DaveM View Post
    The arm on the TPS was rubbing slightly on the throttle body. When it was hot, it would stick at WOT, and hang there until it cooled off some.
    Yep, I understand. I've also seen TPS sensor lever arms that just required a little bending to provide the necessary operating clearance.
    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.

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