Spark Health Check, 2.9 1989 4x4 Auto

[eightynine4x4]

Been meaning to dig a bit into the source of spark and figure out if it’s all there as it should be. The engine still has some random lumpy behaviors I’d like to suss out, especially at startup, and want to eliminate spark from the list of possible causes.

New wires as of the summer, new distributor cap and rotor as of a week ago, new plugs within last few months, timing set to 10 BTDC a few days ago, new ignition coil today.

When I evaluated the old coil I found that the resistance of secondary wasn’t super strong looking, around 7K ohms where as the range should be between 6k and 15k or something like that. So I figured why not pop in a new one since it was cheap and I had some store credit to burn. The old one also looked pretty shoddy so I had concerns about grounding.

I did some cleanup first using contact cleaner on the 4 screws themselves since those were going to be reused, and on the bracket, and on the two items that mount to the side of the bracket.. the grounding wire and what I think is a radio interference cap.

Anyways, I replaced this old crimp terminal with a brand new one and also recut and refreshed the wire end it crimped.

But if that single wire is the source of ground for the entire ignition, I’m concerned about all of the gunk that is involved with this bracket mount and the quality of grounding. So if I have it right.. the ground of the coil unit gets its ground from its large square core, which gets its ground via the 4 screws through it to the bracket that holds the coil unit, which gets its ground from the ground wire terminal that’s crimping the black wire, correct?

I cleaned up the bracket pretty well with electronic contact cleaner and a brush. It didn’t turn out perfect or anything.

Would it be reasonable to add an extra grounding method just to be sure the ignition is as grounded as it needs? Like just add a second beefy black wire that hood over to the chassis nearby?

I guess I’m wondering why there would be a wiring harness extending the ground signal far away for one of the most important parts of the operations of the truck, when it would be quite easy to make a thick jumper to a chassis point or engine block, right?

In any case, I’m also considering going with a “performance” grade coil just to see if it makes a difference. I am relatively confident that this coil improved the spark already. Seems there is a little more power and stability in the engine.

 

[bobbywalter]

Without watching on an occiloscope, I couldn't say how the coil is doing.

What did the chinesium ohm out at?



as to grounding that coil. You may want to study it some more.

Mine was zip tied to a plastic airbox with no ground to chassis wires.....just the cap wire .... And plug

 

[rusty ol ranger]

I believe the ECM does the main grounding of the coil. It uses inputs from various sensors to decide when to ground the coil and fire it.

I had a coil tied to the hood hinge with some random piece of wire for testing purposes at one point. It ran just fine.