No spark... - Team Camaro Tech
Electrical & Wiring Troubleshooting electrical.

 
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post #1 of 8 (permalink) Old Dec 3rd, 08, 09:32 PM Thread Starter
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Paul
 
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Location: Queen Creek AZ
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No spark...

On my 67 EFI camaro...

So I thought that it would be a good idea to move my remote coil from the firewall to the valve cover as I thought maybe the coil could possibly, maybe be throwing some "noise" at the ECU which is mounted directly on the other side of the firewall. So I cut the power wire and had to add a little more to get enough length to mount it on the valve cover.

So, after completing my project the engine won't fire but the coil has voltage with the key on. I had my daughter help me by cranking the engine while I checked the coil power wire with my volt meter to ensure that it is getting power while cranking. Lo and behold the damn thing fires and as long as I keep the volt meter connected from the coil power wire to the valve cover the engine runs...as soon as I disconnect it, the engine dies.

My wiring is a power wire from a junction block on the firewall (connected live to the battery) in to a relay and out to the coil power. The relay is switched by a wire from the fuse block (ignition fused) and grounded to the firewall. My ignition is a GM small body computer controlled distributor with a remote coil (application would be say a 95 chevy truck with a 350). The ECU is a holley commander 950.

So...I'm sitting here scratching my head wondering what stupid thing I did here, LOL!

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post #2 of 8 (permalink) Old Dec 4th, 08, 04:41 AM
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Re: No spark...

Voltmemter is providing a ground to complete the circuit.
Run a ground wire from coil bracket to firewall or to the ECU chassis to complete the circuit.
In fact, you may want to run a ground strap/wire from the engine block to the ECU to put both on the same reference/potential.

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post #3 of 8 (permalink) Old Dec 4th, 08, 07:36 AM Thread Starter
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Re: No spark...

So, the coil bracket has to be grounded...which would mean that the coil needs to be grounded (via the bracket).

I did try a ground wire from the bracket to the manifold and from the coil bracket to the firewall but it still didn't work. I even set the coil on the intake thinking that it would find ground that way but it didn't work.

I wonder if there is one particular part of the coil that needs to be grounded? There are four screws that hold it in place, wondering if one of the four holes is where it gets ground and I have a bad connection there?


P.S. Here is my coil:

http://store.summitracing.com/largei...g=msd-8226.jpg

So in talking to MSD, yes the "E Core" which is the square metal frame around the red coil part does indeed need to be grounded. Whatever grounding I tried last night just didn't give it what it needed I guess...must have had one of those stupid moments or something I suppose as it doesn't seem that grounding that metal frame would be too complex, LOL!

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Last edited by paulm; Dec 4th, 08 at 08:27 AM.
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post #4 of 8 (permalink) Old Dec 4th, 08, 09:27 AM
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Re: No spark...

Voltmemter connected, it runs?
Voltmeter not connected, no run?

Move coil back to original location to see if it runs.
If it does run, why fix it if it ain't broke?..........I know, it's a man thing.

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post #5 of 8 (permalink) Old Dec 4th, 08, 09:43 AM Thread Starter
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Re: No spark...

Ya...total "man thing", LOL!

I'll get it squared away tonight...it's not that complex I guess, I wasn't sure last night whether or not the coil needed to be grounded. Now I'm sure and just have to make sure it's right.

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post #6 of 8 (permalink) Old Dec 4th, 08, 06:01 PM Thread Starter
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Re: No spark...

Well, it was the MSD coil (damn aftermarket parts, LOL)...even with a ground wire it didn't work. Swapped it with my old stocker and just like magic...the engine runs like a champ.

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post #7 of 8 (permalink) Old Dec 4th, 08, 07:16 PM
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Re: No spark...

Hmm......

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post #8 of 8 (permalink) Old Dec 5th, 08, 09:08 PM
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Re: No spark...

That's a stumper. Your description of your wiring technique sounds about right. Almost sounds like your wiring isn't what you expect. I can't imagine how a volt meter could cause it to run. A cheap volt meter has at least 10,000 ohms input impeadance, which won't allow much useful current to flow - certainly not enough to excite a coil. Almost sounds like your coil is wired backward (so your probing ground on the coil) and your meter is on Amps which completes the ground to the valve cover. Make sure your probes are not in the amperage inputs.

Coil frame must be grounded. The ECM should provide power and ground for the coil primary I believe. The coil may have a diode in it that could cause problems if the polarity was reversed. I'm not sure if the primary should be grounded (internally) to the coil frame or not...I would presume not, but get the facts in a service manual. If the primary was grounded to the coil frame, that might say something more about the grounding issues.

Most sensors and servos on a ECM vehichle have their own power and ground (and signal) lines that are isolated from the engine ground except for a shunt wire from the ECM itself to the vehicle chassis.

Dave
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68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI
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