Bad running after manual swap

[JPVortex]

29.5kΩ sounds high (~15kΩ/ft) at least compared to numbers @Schurkey quoted.

I've got some wires downstairs, I'll go measure them.

Do keep in mind, it's a low-current, high-voltage system, so resistance values that don't make any sense in a 12V system are just fine.

Thank you, let me know what you get, deciding if I should get a new set of acdelco wires.

 

[1998_K1500_Sub]

I measured two old sets of wires, one from a 1995 S10 Blazer V6 and the other from a 1995 S10 pickup V6. They were all marked as "7mm" wires.

I measured 3-4 wires from each set, I didn't measure all of them.

I measured using a Fluke 77 multimeter set to autorange. I've owned this meter for almost 40yrs and I trust it to be good.

The S10 Blazer wires are marked with an AC Delco logo, and they measured around 5kΩ/ft. The coil wire, oddly, was only about 1' long and measured 10kΩ.

The S10 pickup truck's wires are marked with a Carquest logo. They measured pretty consistently at 3.5kΩ/ft, except for one which measured open-circuit.

Both these sets are "used" wires replaced on those vehicles.

As for your wires, I would first look for consistency in measurement. Maybe you have a couple of outliers, and you'll find that most measure in the ~5kΩ/ft range... or otherwise. But regardless, I would expect that a good set of wires would be fairly consistent.

I also have a new set of MSD wires in the box downstairs and could measure them if there's any interest.

 

[JPVortex]

I measured two old sets of wires, one from a 1995 S10 Blazer V6 and the other from a 1995 S10 pickup V6. They were all marked as "7mm" wires.

I measured 3-4 wires from each set, I didn't measure all of them.

I measured using a Fluke 77 multimeter set to autorange. I've owned this meter for almost 40yrs and I trust it to be good.

The S10 Blazer wires are marked with an AC Delco logo, and they measured around 5kΩ/ft. The coil wire, oddly, was only about 1' long and measured 10kΩ.

The S10 pickup truck's wires are marked with a Carquest logo. They measured pretty consistently at 3.5kΩ/ft, except for one which measured open-circuit.

Both these sets are "used" wires replaced on those vehicles.

As for your wires, I would first look for consistency in measurement. Maybe you have a couple of outliers, and you'll find that most measure in the ~5kΩ/ft range... or otherwise. But regardless, I would expect that a good set of wires would be fairly consistent.

I also have a new set of MSD wires in the box downstairs and could measure them if there's any interest.

Yeah these things are junk, they’re NAPA brand, I’ve tested all of them now.

All over the board, most are 2-2 1/2ft long.

I’m getting measurements from 33ohms across the whole thing, to then 16 or 17, and one was 11.

 

[JPVortex]

I measured two old sets of wires, one from a 1995 S10 Blazer V6 and the other from a 1995 S10 pickup V6. They were all marked as "7mm" wires.

I measured 3-4 wires from each set, I didn't measure all of them.

I measured using a Fluke 77 multimeter set to autorange. I've owned this meter for almost 40yrs and I trust it to be good.

The S10 Blazer wires are marked with an AC Delco logo, and they measured around 5kΩ/ft. The coil wire, oddly, was only about 1' long and measured 10kΩ.

The S10 pickup truck's wires are marked with a Carquest logo. They measured pretty consistently at 3.5kΩ/ft, except for one which measured open-circuit.

Both these sets are "used" wires replaced on those vehicles.

As for your wires, I would first look for consistency in measurement. Maybe you have a couple of outliers, and you'll find that most measure in the ~5kΩ/ft range... or otherwise. But regardless, I would expect that a good set of wires would be fairly consistent.

I also have a new set of MSD wires in the box downstairs and could measure them if there's any interest.

Ok I’ve tested 6 NAPA wires, these are the results:

6,000 ohms/ft

7,000 ohms/ft

9,000 ohms/ft

10,000 ohms/ft

13,000 ohms/ft

9,000 ohms/ft


Think it’s safe to say they need replaced.

 

[1998_K1500_Sub]

Ok I’ve tested 6 NAPA wires, these are the results:

6,000 ohms/ft

7,000 ohms/ft

9,000 ohms/ft

10,000 ohms/ft

13,000 ohms/ft

9,000 ohms/ft


Think it’s safe to say they need replaced.

@Schurkey said "Anywhere from ~35 ohms per foot of wire, to 4,000 ohms per foot" so yours may be considered "high".

Were any of them open circuit???

Do you trust your meter? Can you measure a known resistance, preferably one in the 2kΩ to 10kΩ range, to verify the meter's "good" or at least "in the ballpark"?

 

[JPVortex]

@Schurkey said "Anywhere from ~35 ohms per foot of wire, to 4,000 ohms per foot" so yours may be considered "high".

Were any of them open circuit???

None of them seemed to be an open circuit. Im going to go ahead and put 8 ACDelco's in there and see what happens.

I also got a Delphi coil today and it seems to have solved the bouncing tach issue, but has not resolved the poor idle/wanting to die when the coil is next to the intake and cap, still runs okay when I hold the coil away from the metal.

 

[1998_K1500_Sub]

Have you checked the resistance between (1) the "ground" wire that leads to the coil and (2) the engine block? The coil's secondary needs a path to "ground" on the engine block to complete the secondary (high-voltage, "spark") circuit.

I need to look, but IIRC the coil gets grounded to the engine via its connection to the ICM. The ICM in turn is physically connected to the dizzy via two screws. From there, the electrical path to the engine block is probably via the dizzy hold-down bracket.

I think this is the wiring diagram for your year ignition. The ground connection is illustrated as being via the ICM's hold-down screw (to the dizzy).

You must be registered for see images attach

 

[JPVortex]

Have you checked the resistance between (1) the "ground" wire that leads to the coil and (2) the engine block? The coil's secondary needs a path to "ground" on the engine block to complete the secondary (high-voltage, "spark") circuit.

I need to look, but IIRC the coil gets grounded to the engine via its connection to the ICM. The ICM in turn is physically connected to the dizzy via two screws. From there, the electrical path to the engine block is probably via the dizzy hold-down bracket.

I think this is the wiring diagram for your year ignition. The ground connection is illustrated as being via the ICM's hold-down screw (to the dizzy).

You must be registered for see images attach

I can check the resistance there, but I did just replace the whole dizzy with a new icm, cap, rotor etc like 3 days ago.

 

[1998_K1500_Sub]

I can check the resistance there, but I did just replace the whole dizzy with a new icm, cap, rotor etc like 3 days ago.

It never hurts to check.

Wiggle wires when you check.

He!!, measure anything and everything you can. You've got something funky going on with that IGN system.

The fact someone's ****'d with the wiring harness (prior owner, as you mentioned earlier, I think in the context of the power wire from the IGN switch) makes anything and everything suspect.

 

[1998_K1500_Sub]

@Schurkey, are you out there?

Can you explain to me how the secondary HV circuit is completed from the coil, to the spark plug, to the block, and then back to the coil? The last path -- engine block back to the coil -- isn't obvious to me. I've never seen it plainly highlighed in a schematic.

It would seem it's through the ICM, that's the only device that's connected both to the coil (both primary and secondary) and the engine block.

Evidently the return path is not through the coil bracket, as that's an open circuit (supposed to measure ∞) between the coil and the bracket.