Commander 950 guys, quick question.
Thread Starter
Burning Brakes
Joined: Oct 2001
Posts: 1,185
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From: New Wilmington PA
Commander 950 guys, quick question.
Above is a picture of the diagram in the Holley manual. I just got a coil wire today from Pace stock for early 90's trucks/camaros, on one end it has the connector for the coil and on the other side, the connector for the distributor. The manual shows a third, switched 12v+, wire attached to the pink wire side of things. Should I tap the pink wire and attach my old dist + to it? Why doesn't the stock GM setup need this. As I understand it the coil I have is a direct drop-in replacement for cars with a CC distributor.
Thanks guys. Sorry to bother, it took a lot of hunting to find this simple connector, hate to start chopping it up if I don't need to.
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Joined: Sep 1999
Posts: 11,361
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From: Plano TX
Re: Commander 950 guys, quick question. (Cookwithvette)
The diagram is somewhat simplified. I'll try to explain the stock late model setup and hope I can do it well enough to make sense...
The wire you have goes from the 2 pin distributor connector to the coil. Sofar so good. The pink wire feeds 12V TOWARDS the distributor. The white wire fires the coil (ground).
Now if you look at a late model coil you will see it has TWO connectors with 2 pins on each. One of them is used for the wire you got. The second connector feeds the coil 12V from the ignition switch and the last pin is for your tach. Inside the coil the two connectors are parallell. This means that the two top pins are connected as well as the two bottom pins between the connectors.
How this works is that you feed 12V from the ignition switch to the coil. INSIDE the coil you have a connection to the corresponding pin on the second connector. From this second connector the 12V is then forwarded to the distrbutor via the pink wire.
Going from the distributor the white wire is the coil trigger (ground). It goes to the coil to fire it, but this pin is also connected to its corresponding pin and then out the second connector to your tach.
Hope I made some sense...
The wire you have goes from the 2 pin distributor connector to the coil. Sofar so good. The pink wire feeds 12V TOWARDS the distributor. The white wire fires the coil (ground).
Now if you look at a late model coil you will see it has TWO connectors with 2 pins on each. One of them is used for the wire you got. The second connector feeds the coil 12V from the ignition switch and the last pin is for your tach. Inside the coil the two connectors are parallell. This means that the two top pins are connected as well as the two bottom pins between the connectors.
How this works is that you feed 12V from the ignition switch to the coil. INSIDE the coil you have a connection to the corresponding pin on the second connector. From this second connector the 12V is then forwarded to the distrbutor via the pink wire.
Going from the distributor the white wire is the coil trigger (ground). It goes to the coil to fire it, but this pin is also connected to its corresponding pin and then out the second connector to your tach.
Hope I made some sense...
Thread Starter
Burning Brakes
Joined: Oct 2001
Posts: 1,185
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From: New Wilmington PA
Re: Commander 950 guys, quick question. (zwede)
Thank you thank you thank you!!!! :hurray: That does make sense. I was fiddling around with a multimeter and wondered why the top two holes and bottom two holes read as a dead short. I had figured it had something to do with an MSD control box since it's an MSD coil.
Thank you so much, I really appreciate it. :cheers:
Thank you so much, I really appreciate it. :cheers:
Le Mans Master
Joined: Aug 2000
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From: Brazos TX
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Re: Commander 950 guys, quick question. (Cookwithvette)
My ignition system is still not working. My coil is a Holley street avenger and it only has 1 + and 1 - terminal like most coils. I have switched 12v going to the + and the pink wire split from that going to the dist. The - is run to the other side of the dist. and the tach is also split off of it.
What is strange is that the instructions for the coil tell you to run a ground wire from the - side of the coil, to an engine ground. Yet the diagram in the EFI manual doesn't show this. Any thoughts?
Are you running an MSD coil, zwede?
What is strange is that the instructions for the coil tell you to run a ground wire from the - side of the coil, to an engine ground. Yet the diagram in the EFI manual doesn't show this. Any thoughts?
Are you running an MSD coil, zwede?
Race Director
Joined: Sep 1999
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From: Plano TX
Re: Commander 950 guys, quick question. (burners)
Are you running an MSD coil, zwede?
The way you have it hooked up should work. Have you measured the pink wire to make sure you really are getting 12V to it? Although I think you said in an earlier post that you see an rpm reading on the C950 while cranking which would mean the distributor is getting juice.
If you hook a timing light to the coil wire, will it flash while cranking?
Le Mans Master
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From: Brazos TX
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Re: Commander 950 guys, quick question. (zwede)
Zwede, I'm definitely getting 12v to the coil and distributor. I haven't connected the timing light directly to the coil wire but nothing is coming out to #1 cylinder. I think the trigger module is cooked but I'm not sure how that happened.
Based on the troubleshooting guide RPM signal is verified by the fuel pump turning on but it doesn't say when. There is the initial "pump on" feature to pressurize the system for 10 seconds. It does that, however it doesn't seem to turn the pump on once the engine is cranked over. I'm not sure if this has changed or not. I thought the pump was coming on before. Does the initial pressurization sequence use the RPM signal to start? If not then I've probably been dealing with a faulty trigger module from the beginning. Where does the ECM get the RPM signal from?
I'm thinking about installing an old points type distributor that has a Pertronix trigger module in it just to get the EFI running. I'll worry about the HEI later. I'm just trying to figure out how to wire it. Any thoughts on that?
Based on the troubleshooting guide RPM signal is verified by the fuel pump turning on but it doesn't say when. There is the initial "pump on" feature to pressurize the system for 10 seconds. It does that, however it doesn't seem to turn the pump on once the engine is cranked over. I'm not sure if this has changed or not. I thought the pump was coming on before. Does the initial pressurization sequence use the RPM signal to start? If not then I've probably been dealing with a faulty trigger module from the beginning. Where does the ECM get the RPM signal from?
I'm thinking about installing an old points type distributor that has a Pertronix trigger module in it just to get the EFI running. I'll worry about the HEI later. I'm just trying to figure out how to wire it. Any thoughts on that?
Race Director
Joined: Sep 1999
Posts: 11,361
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From: Plano TX
Re: Commander 950 guys, quick question. (burners)
The initial fuel prime is triggered by 12V to the ECM. It does not use the rpm signal for this.
Hook up a laptop and look at the real time rpm readout while cranking. If it stays at 0 you have a bad module or wiring. The rpm signal to the ECM comes from the 4 pin connector on the HEI.
Also, make sure the C950 is setup for HEI. Pull up the "engine parameters" screen and there's a choice for ignition type. If it is set wrong the ECU will expect the rpm signal on a different pin and the engine won't start.
Hook up a laptop and look at the real time rpm readout while cranking. If it stays at 0 you have a bad module or wiring. The rpm signal to the ECM comes from the 4 pin connector on the HEI.
Also, make sure the C950 is setup for HEI. Pull up the "engine parameters" screen and there's a choice for ignition type. If it is set wrong the ECU will expect the rpm signal on a different pin and the engine won't start.
Le Mans Master
Joined: Aug 2000
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From: Brazos TX
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Re: Commander 950 guys, quick question. (zwede)
I've been running the start proceedure and watching it in real-time on the laptop from the first time we tried to start it. The setup has been set to HEI. It is not reading an RPM now. I think we are in agreement that the module (or something) is shot. Any idea how to wire a Pertronix distributor? I see in the schematic that there is a pin for "points out" but I'm not sure if that's what I want. It's in the IPU connector. I can't find a description for what the IPU connector is for.
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Le Mans Master
Joined: Aug 2000
Posts: 6,362
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From: Brazos TX
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Re: Commander 950 guys, quick question. (burners)
Ok, I just got off the phone with Holley tech and I connect the - side of the coil to the yellow wire in the harness. That will give the ECU the RPM signal. This is for the Pertronix setup. So I'm off to give this a try (after dinner). Hopefully I'll be back in a few hours with some good news.
