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Discussion Starter · #1 ·
Started testing the various things.

First, heres the settings on my meter:



With the meter set at 200, I measured between TACH and BATT, this was the reading, which seems in spec:


But then I switched the meter to a higher setting, and measured between TACH and the coil center nub, and then between BATT and the coil center nub, like this, with these readings:


No matter where I set the ohmmeter, I get the same reading on this test.

Those are the same readings the meter reads when it's not hooked up to anything. Is that infinity?

Do those readings mean the coil is bad?

That would be odd, because this is a brand new cap/coil. Also, I tried the same test on the old cap/coil, and got the exact same readings. The old cap/coil were working fine when removed from the car a month aqo.

Thoughts? Thanks!
 

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Doc here, :pimp:

Unless the pictures are deceiving, your meter is set wrong..

It looks like in the first one it is set to OFF..

And in the second one it is set to Volts not ohms (which is 180 around from the Volts scale)

Test the meter, short the probes set on OHMS..it should read 000, then infinite whit the probes open...Then set the meter for OHMS (bottom left) R X ! scale, do the primary...less than an ohm..but more than 000.

Then set the scale for R X 10 K of higher, and do the secondary, it should read 6,000 to 30,000 ohms..

Doc :pimp:
 

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Discussion Starter · #3 ·
Hi Doc, the pics aren't very clear, but you are looking at the wrong end of the knob.

In the first 2 pics, it is set to 200 Ohms.

In the second 2 pics, it is set to 20k Ohms.

With that in mind, what do you think of the readings in the pictures?
 

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Doc here,

ARE you SURE it is set to 200 ohms??

The Rounded end to me seems like it would be the index pointer, and the indented end seems like it would be the rear of the index pointer..

try this: short the probes like it is set in pic 1, DOES the readout go to "000" and hold? IF NOT, reverse the index pointer, and do it again, if it goes to "000" then it's 180 off scale....


Doc :pimp:
 

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Discussion Starter · #5 ·
Yep, I'm sure.

Isn't the second pic proof enough for ya, Doc! If that were off, it wouldn't be showing 00.9 on the screen! ;)

But to put your doubting mind to rest:

Here's set at 200 ohms with the prongs grounded together. For some reason, it sometimes goes to 000, but sometimes not quite.


And here's at 2000 ohm. At this setting, it goes to 000 when grounded.



And here's OFF. It goes to blank screen! :)


So, I'm getting infinity ohms when measuring between BATT and the center nub, and infinity ohms when measuring between TACH and the center nub.

This seems to indicate a bad coil, no?

But isn't it odd to have TWO bad coils? One on my brand new coil, and the other on my old one that worked fine when removed a month ago?

And if the readings indicate conclusively that both are bad, is there something on my car that is blowing them up? Or it is likely just a coincidence?
 

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Doc here, :pimp:

Use the 2000 ohm setting...something is not right worth the 200 ohm setting, it may have be overloaded at somepoint..it should read "000" there like it does on the 2000 ohm setting (unless your battery is weak)

If it reads 1.0 on the secondary, the coil is shorted...toss it. If it reads infinity on the secondary, the coil is blown open..toss it..

The readings should be..about Primary: 0.30 to 0.90 (or close to it) with meter set to 2000 ohms, and with the meter set to 20k ,the SECONDARY should read..6,000 to 30,000 ohms..(or close to it)

Anything else is a bad coil, OR it is shorted inside the cap when it was installed to ground (check to be sure)

Bad coils aren't uncommon out of the box but I'd check BOTH, to be sure the old one may not be bad at all.

Doc :pimp:
 

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Discussion Starter · #7 ·
Hmm. I went to the parts store and tested some of the coils they had, and got the same readings as mine.

I took the distributor out of the car, and using a set of jumpers, attached the negative post of the battery to the distributor body, and + to the BATT post on the distributor, and gave it a spin. It sparked pretty good.

So the distributor seems to be working . . .

I think next I'll try putting it back in the car, and running it with a direct ground from the negative post of the battery to the body of the distributor, and a direct line from the postive post of the battery to the BATT post on the distributor.
 

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Discussion Starter · #8 ·
Well, I thought that was going to work for sure, but it didn't.

How can I be getting spark when I take it off the car and attach it directly to the battery, but no spark when I put it back in the car, but still drive it directly off the battery?!?

I'm not getting weak spark, I'm getting no spark at all. (Earlier today, I did notice at least some very weak sparking at the plug that I had pulled).
 

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Do you have a good ground from the battery to the block? Then make sure you have a good wired connection from the alt to the block too. Too many let the mechanical connections be the electrical and that sometimes don't work so well.
 

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Discussion Starter · #10 ·
Yes, the ground from the battery to the block is good, it is all new hardware and cabling.

The grounding from the alternator to the block, hmm, I don't see any, that seems to rely on mechanical connections. And the alternator is held to the block by way of a long aluminum bracket. Is that not sufficient? (That is how the car has run for 14 years).

Also, I intend to test run the distributor off a completely separate battery. If I connect the + post on that battery to the BATT post on the distributor, and connect the - post on the battery to the body of the distributor (using jumper cables), the distributor should fire, correct?
 

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Porschev said:
Hmm. I went to the parts store and tested some of the coils they had, and got the same readings as mine.

I took the distributor out of the car, and using a set of jumpers, attached the negative post of the battery to the distributor body, and + to the BATT post on the distributor, and gave it a spin. It sparked pretty good.

So the distributor seems to be working . . .

I think next I'll try putting it back in the car, and running it with a direct ground from the negative post of the battery to the body of the distributor, and a direct line from the postive post of the battery to the BATT post on the distributor.
Doc here, :pimp:

First off, your OHMS scale on your meter may be damaged, it may at some point got an accidental DC voltage and fried the precision resistors inside the meter, at any rate , It doesn't sound right, AND I wouldn't trust it until you have it checked out..

Doc :pimp:
 

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Discussion Starter · #13 ·
I agree - although the meter seems to read correct on some measurements (for example, the measurements between the BATT and TACH prongs shown in the pictures above seem to be accurate), something seems wrong with the meter and I am no longer relying on it.
 

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Porschev said:
Well, I thought that was going to work for sure, but it didn't.

How can I be getting spark when I take it off the car and attach it directly to the battery, but no spark when I put it back in the car, but still drive it directly off the battery?!?

I'm not getting weak spark, I'm getting no spark at all. (Earlier today, I did notice at least some very weak sparking at the plug that I had pulled).

Doc here, :pimp:

Because the Module as well as the coil relies on a good ground..If your engine as well as your Dizzy is not getting THE SAME good ground, it won't fire..REMEMBER: The PLUGS share the same ground..

A weak coil may provide enough of a jolt to fire ONE plug with a spark, but not enough to fire 8..with a usable spark.

If the module were going thermal, It may be shutting down after a few seconds..Did you have that tested?

Doc :pimp:
 

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Discussion Starter · #15 ·
Big Mouse said:
Have you checked the ignition module in the HEI? If you don't have a spare one, beg borrow or steal one. A bad module will stop an HEI dead in its tracks.
But doesn't the fact that it sparks like crazy when I take it off the car and hook it up directly to the battery, as described in my post above, mean that that module and the HEI are good?

("I took the distributor out of the car, and using a set of jumpers, attached the negative post of the battery to the distributor body, and + to the BATT post on the distributor, and gave it a spin. It sparked pretty good.")
 

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I've had cars that the module in the HEI did some strange things. That is why I suggest borrowing one if you can - because I'm not sure ;)

Also, did you put dielectric grease under the module before you installed it?
 

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Discussion Starter · #17 ·
docvette said:
Doc here, :pimp:

Because the Module as well as the coil relies on a good ground..If your engine as well as your Dizzy is not getting THE SAME good ground, it won't fire..REMEMBER: The PLUGS share the same ground..

A weak coil may provide enough of a jolt to fire ONE plug with a spark, but not enough to fire 8..with a usable spark.

If the module were going thermal, It may be shutting down after a few seconds..Did you have that tested?

Doc :pimp:
I don't think it's a ground problem, because the engine is well grounded. I have all new battery and ground cables, hooked up to everything using all new hardware. Everything is very clean and tight.

The coil, or the module, or something else in the distributor, may be weak. I've called every NAPA, Pep Boys, Kragen, etc. in my area, and none of them say they can test it!
 

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Porschev said:
Yes, the ground from the battery to the block is good, it is all new hardware and cabling.

The grounding from the alternator to the block, hmm, I don't see any, that seems to rely on mechanical connections. And the alternator is held to the block by way of a long aluminum bracket. Is that not sufficient? (That is how the car has run for 14 years).

Also, I intend to test run the distributor off a completely separate battery. If I connect the + post on that battery to the BATT post on the distributor, and connect the - post on the battery to the body of the distributor (using jumper cables), the distributor should fire, correct?
Doc here, :pimp:

Even though it ran fine for 14 years...you just had it out..a lot of things can change!

For grounding:

Run a properly gauged Ground cable from the battery to any handy bolt at or near the starter, From that same bolt get a 4 Ga Battery cable at the parts store, that has two 3/8 ring terminals on each end and attach it there and to the Frame.

Next get some 10 gauge wire and ring terminals and run that from your bolt on the block to the Firewall, and another to the Alternator bracket or mount bolt or Grounding lug on the alternator..


HOLE #4 ON THE ILLUSTRATION IS GROUND.

Next get some Wire Braid, (Radio Shack) and install braid from the radiator support to the frame, Fenderwells to frame , hood to firewall, Doors to door posts, gas flap to body, tailgate / Trunk to body.

At each point the wire is grounded, Burnish ALL the paint and grease off to bare metal. Use a proper star-washer and lock. Use sheetmetal or Tech screws where no screws are available.

For testing the coil,




The module can be tested at the Auto parts store, (while your getting grounding supplies) and have it done several times to be sure it is warm and not going thermal....

Another possibility, is if the TACH wire were shorted some where in the body, OR if the calibration card in the tach were going south, Do all your testing with the tach wire OFF at the cap...a bad tach / wire will reduce or kill spark.

Lastly, If all else fails, check the magnetic pickup, inside the dizzy, bad, or intermittent or bent out of adjustment as well as any magnetic shavings can kill spark too..you HAVE to disassemble the Dizzy to repair or replace this part.

Doc :pimp:
 

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Porschev said:
I agree - although the meter seems to read correct on some measurements (for example, the measurements between the BATT and TACH prongs shown in the pictures above seem to be accurate), something seems wrong with the meter and I am no longer relying on it.

Doc here, :pimp:

If your refering to the "1" on the readout in the photo...

That is ABOVE maximum value..the spec is LESS than an ohm..more like 0.60 Ohms is what your looking for.

Doc :pimp:
 

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Porschev said:
I don't think it's a ground problem, because the engine is well grounded. I have all new battery and ground cables, hooked up to everything using all new hardware. Everything is very clean and tight.

The coil, or the module, or something else in the distributor, may be weak. I've called every NAPA, Pep Boys, Kragen, etc. in my area, and none of them say they can test it!
Doc Here, :pimp:

Even the slightest grounding issue can cause resistance to the devices it supplies, which translates to the AMP inside the module not running at full value..The module is a Buffer, and high speed switching amplifier..If it were seeing a bad ground it may not be fully operative. (weak, No spark). Do you have another GM vehicle RUNNING that shares the same parts? Swap them ONE AT A TIME to verify they are good...

Doc :pimp:
 
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