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Thread: Commander 950 Not Priming

  1. #1

    Default Commander 950 Not Priming

    Hello. I have a Holley Commander 950 installed in a '69 Mustang. I installed the system 7 years ago, and it has run without any major issues. In the past few months, the system will not prime the fuel pump with key on. I have the ECU set to prime for 4.9 seconds. Again, this has always worked.

    In troubleshooting, I've tested the relays (both the system supplied as well as a relay I installed at the fuel pump).
    In probing the wires going into the ECU directly:
    I have 12 volts at the red wire.
    I have 12 volts at the red/white wire when the key is on.
    I do not have any voltage at the green/black striped wire during key on, when the system does not prime.
    When the system does prime, I'm getting 12 volts on the green/black stripe wire.

    The problem is intermittent and I cannot seem to reliably make it prime. It seems to work for awhile and then quit. Of course, it quits when I'm parked away from my home.

    If I'm getting 12 volts at the green wire when it works and not when it doesn't, does that give any clues? I've checked & cleaned ground wire and looked for any other obvious issues without success.

    The only other clue I can provide is, I don't seem to be able to get the laptop connected to the ECU when the system isn't priming. I'm able to connect them when the system primes & starts.

    I'd appreciate any help troubleshooting this, as I can't drive the car with the risk it will leave me stranded unable to start during intermittent issue. Thanks in advance.

  2. #2
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    Quote Originally Posted by jeffawarner View Post
    I do not have any voltage at the green/black striped wire during key on, when the system does not prime.
    When the system does prime, I'm getting 12 volts on the green/black stripe wire.
    The problem is intermittent and I cannot seem to reliably make it prime. It seems to work for awhile and then quit.
    I would start by performing a continuity & wiggle test on the main harness. Also, check the ECU connector & its terminals for a bad connection. Check the system relay terminals for corrosion too.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  3. #3

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    Thanks Danny, I appreciate the response. I've checked the ECU connector & terminals, and the system relay terminals as well. I have wiggled wires across the harness and it didn't seem to change the conditions. It is odd because it's so unpredictable. I will do the continuity test on the main harness. Two follow-up questions:
    1) On the continuity test, for the system to prime, are there specific conditions I should look for (wires that may be more suspect that are required for the system to prime)? I'm trying to target my search.
    2) Is there any way to test the ECU? I'm just looking for a way to rule out that the ECU is failing. Thanks again! Jeff

  4. #4
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    Quote Originally Posted by jeffawarner View Post
    1) On the continuity test, for the system to prime, are there specific conditions I should look for (wires that may be more suspect that are required for the system to prime)?
    Red/white +12V switched wire (ECU A6 pin), and green/black fuel pump relay trigger wire (ECU A2 pin). Of course, the main battery power (fused) & ground must be good too.
    http://documents.holley.com/techlibrary_r10149-7.pdf (Holley Commander 950 Pro EFI Manual - Figure 86, Page 111)

    2) Is there any way to test the ECU? I'm just looking for a way to rule out that the ECU is failing.
    I don't know if Holley still tests C950 ECUs. If everything checks out (wiring & relay), you probably have a defective ECU.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  5. #5

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    I'm pretty sure I had one flashed & tested about 3 years ago. I had bought a spare off eBay. If it turns out you need an ECU, I have two. I upgraded to the HP EFI ECU.

  6. #6

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    Thanks guys. I appreciate the help. I'm still having no luck. I will call Holley on Monday and see what the options are. I'll come back to you if it turns out it's a bad ECU. By the way, I haven't dug into the HP EFI. Is the HP EFI worthwhile for me to consider instead of fixing/replacing the C950? I'm running TBI on my Ford FE engine. I'm interested in how easy the upgrade is and what the benefits are for TBI. Thanks again!
    Last edited by jeffawarner; 11-26-2016 at 10:53 AM.

  7. #7
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    Quote Originally Posted by jeffawarner View Post
    By the way, I haven't dug into the HP EFI. Is the HP EFI worthwhile for me to consider instead of fixing/replacing the C950?
    Absolutely yes!

    I'm running TBI on my Ford FE engine. I'm interested in how easy the upgrade is and what the benefits are for TBI.
    Is this Ford FE the engine in your '69 Mustang? If so, then you already know the TBI benefits. The upgrade doesn't involve replacing the TBI unit.
    https://www.holley.com/products/fuel.../parts/550-606 (Holley HP EFI ECU & Harness Kit)
    https://www.holley.com/products/fuel.../parts/558-205 (Holley 4BBL TBI Fuel Injector Harness)
    http://forums.holley.com/showthread....0448#post80448 (Related Forum Thread)
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  8. #8

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    Depends on if you were happy with the Commander 950. I went HP to get "self-tuning/Learning" mostly. I think when I did mine, the ECU/harness kit cost me about 1200? But that was over 3 years ago I believe. (My car has been apart after painting.) For me, if I could have figured out how to program the C950 by myself, I probably would not have upgraded.

  9. #9
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    I was very well versed with the Holley Commander 950 EFI, but it's no comparison to the Holley HP EFI.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  10. #10

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    Thanks for the input guys. Yes, the TBI is in my Ford FE engine. I really like the concept of the Commander 950, but admit I've never really been able to get it dialed in. I have a buddy in another town who has visited me a couple times, who is very familiar with it and has helped me on occasion. The concept of self-tuning/Learning is really appealing.

    The one thing I've struggled with is spark control. I have a cobbled together spark control system. When I put the system in 7 years ago, there really wasn't an easy way to manage spark. It don't think I could find a crank trigger and I used a Holley adapter and Accel ignition system out of an '80s Chevy pickup. It was a sort of dog's breakfast of parts to try to control spark. Any advice as to a more proven method? How would that fit with the HP EFI?

    Thanks again. Good to hear the advances in Holley's offering. I was sort of off the EFI grid for 5-6 years.

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