Ignition coil questions...

Red left me on the side of the road earlier today. I was stopped at a light in neutral and my idle around 800 per the dash gauge. Without warning the RPMs dropped to 0 and she wouldn't crank back up. I pushed her off to the side and tinkered a little. A guy in a very nice fox body Mustang stopped and was admiring the D while he was listening to the engine. He pointed at my silver Accell coil and said "That's the source of your problem. I've pulled many of those out of the Mustangs I repair and I've never seen one run right." I pulled the wire, reseated it, and Red fired right up.

On the way home I kept the radio off and listened to the engine closely. From about 2500 RPM up I could hear a misfire and could feel it in the car. Anything up to that point was surprisingly strong for a car that had just left me on the road.

Going from memory of the last time I put a multimeter on that coil I had 1.8 volts on the left hand side and about 7.5 or so from the right hand side. This was key on but not cranked. I'll have to take readings tomorrow when she's running. Last time I was messing with it I was so excited that Red started that I forgot what I was doing and took her for a short drive. I blame Delorean withdrawl...

Are you sure you have the ignition coil correctly oriented? On some aftermarket coils you have to face the coil "backwards" (label against the firewall) to get the positive and negative terminals in the correct orientation for our cars. (You can run a car with the ignition coil wired backwards, but it will run like doo-doo.)

Farrar

Use the terminal markings (+ and -). That's what they are there for. Orienting a coil by a brand label means absolutely nothing -- what if there was no label?

Is your "left side" positive or negative? If you're only running 1.8 volts into the coil (obviously the ECU side of the circuit), your secondary spark is going to be very weak indeed.

Bill Robertson
#5939

Quote:

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Originally Posted by content22207

Orienting a coil by a brand label means absolutely nothing...

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Nonetheless, I've seen people do it... :shrug:

It never hurts to rule out the obvious.

Farrar

Quote:

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Originally Posted by Farrar

It never hurts to rule out the obvious.

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True Dat! It is easy to become complacent with things like that and you can never assume the skill level of the OP's ability. But really, gotta pay attention to the hard markings on the coil.

I matched it up by positive and negative when I took off the old coil. However, I should have taken into account the previous owner's ability. He did have a mismatched set of plugs in the car. I could easily have a backwards coil and not know it. I'll trace the wires when I get home and make the ECU side is heading into the positive terminal.

If the coil is oriented correctly and I am only getting 1.8 into the ECU side then I'll need to search for the source of that low voltage. Is there a voltage range I should be looking to see off that terminal?

Quote:

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Originally Posted by Kenny_Z

I pulled the wire, reseated it, and Red fired right up.

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Are you talking about the wire that goes from the ignition coil to the distributor? This wire has come loose on my ignition coil before. I decided to fasten the wire with a tie wrap and it hasn't been loose since then.

Quote:

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Originally Posted by Kenny_Z

I'll trace the wires when I get home and make the ECU side is heading into the positive terminal.

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If you do that your ignition will never work right, no matter what brand of coil you use.

Bill Robertson
#5939

Yeah, the wire from the coil to the distributor. I did have an issue with the cable walking up the coil's connection during my tune up until I spread the metal connector enough to hold the wire down. The boot John put on that cable is too small for after market coils.

Even with it fully secured I feel like I've got a weak spark.

You've got a weak spark because you wired your coil up backwards.

Line in comes from the resistor grid. Line out goes to the ECU.

Bill Robertson
#5939