Testing Ignition Coil (1984 GMC 1500 Sierra Classic)

On Wed, 9 Aug 2006 23:11:22 -0700, "Big Al" <sal1 RemoveThis @qwest.net> wrote:
>
>Before you do that, check the rotor. It may be punctured and arcing. If it's
>bad, check the plug wires...
>
>Al

Al,

Thanks for the response. Will the rotor show any physical signs of
problems? Also, if it turns out to be bad, what's the best way to test
the plug wires?

-- Christian
 >> Stay informed about: Testing Ignition Coil (1984 GMC 1500 Sierra Classic) 

unless you have some fancy equipment, I look under the hood when it is dark
outside. Engine running. Sometimes you will see what looks like fire flies
jumping all over the place. Or just one wire is bad, like the coil wire.

--
remove one of the @'s unless you are a spammer.
"CMM" <newsgroupinky.TakeThisOut@hotmail.com> wrote in message
news:8gomd21ct4l04egri4tc49a4pbhs37u8f9@4ax.com...
> On Wed, 9 Aug 2006 23:11:22 -0700, "Big Al" <sal1.TakeThisOut@qwest.net> wrote:
>>
>>Before you do that, check the rotor. It may be punctured and arcing. If
>>it's
>>bad, check the plug wires...
>>
>>Al
>
> Al,
>
> Thanks for the response. Will the rotor show any physical signs of
> problems? Also, if it turns out to be bad, what's the best way to test
> the plug wires?
>
> -- Christian
 >> Stay informed about: Testing Ignition Coil (1984 GMC 1500 Sierra Classic) 

On Thu, 10 Aug 2006 12:52:14 -0400, "Bill" <bargerw@@bellsouth.net>
wrote:

>unless you have some fancy equipment, I look under the hood when it is dark
>outside. Engine running. Sometimes you will see what looks like fire flies
>jumping all over the place. Or just one wire is bad, like the coil wire.

He went ahead and replaced the coil and rotor. He's pretty much just
throwing money at it, hoping something will work. Neither of those
things did, unfortunately.

The coil on this one is integrated and doesn't have a wire that feeds
the diistrbutor. I'm going to have him check now the wires that feed
the coil to see if they have power.

-- Chrisitan
 >> Stay informed about: Testing Ignition Coil (1984 GMC 1500 Sierra Classic) 

"CMM" <newsgroupinky DeleteThis @hotmail.com> wrote in message
news:gf4nd2lbflrcurpuvd3i9i100gsr7b4n7e@4ax.com...
> On Thu, 10 Aug 2006 12:52:14 -0400, "Bill" <bargerw@@bellsouth.net>
> wrote:
>
> >unless you have some fancy equipment, I look under the hood when it is
dark
> >outside. Engine running. Sometimes you will see what looks like fire
flies
> >jumping all over the place. Or just one wire is bad, like the coil wire.
>
> He went ahead and replaced the coil and rotor. He's pretty much just
> throwing money at it, hoping something will work. Neither of those
> things did, unfortunately.
>
> The coil on this one is integrated and doesn't have a wire that feeds
> the diistrbutor. I'm going to have him check now the wires that feed
> the coil to see if they have power.
>

Future reference. The rotor can be visually inspected after removal,
turn it over and look at the bottom side center, will look charred. Look
for signs of "red dust" in the cap and on the distributor, This is caused
by the spark shooting down through the rotor and arching off things, like
the advance weights around
their pivot pins..If there is a lot of it in there, the ignition module
maybe damaged as well,
and even the pick up coil for that matter.
Don't buy cheap caps and rotors for GM. Stick with AC Delco,
Standard Ignition, the Blue Streak line, (excuse me Standard Ignition is
now Standard Motor Company) not the regular stuff, and of all places
AutoZone
carries a high end line that holds up pretty good., Gold, part number is
DR2001G, sold as set only. .NAPA has two lines, red by Echlin, and blue by
standard. Echlin stay away from on GM, fine on Ford or Chrysler.

Whitelightning
 >> Stay informed about: Testing Ignition Coil (1984 GMC 1500 Sierra Classic) 

CMM wrote:
> On Thu, 10 Aug 2006 23:19:39 GMT, "Whitelightning"
> <white.lightning2.RemoveThis@verizon.net> wrote:
> >
> >Future reference. The rotor can be visually inspected after removal,
> >turn it over and look at the bottom side center, will look charred. Look
> >for signs of "red dust" in the cap and on the distributor, This is caused
> >by the spark shooting down through the rotor and arching off things, like
> >the advance weights around
> >their pivot pins..If there is a lot of it in there, the ignition module
> >maybe damaged as well,
> >and even the pick up coil for that matter.
> > Don't buy cheap caps and rotors for GM. Stick with AC Delco,
> >Standard Ignition, the Blue Streak line, (excuse me Standard Ignition is
> >now Standard Motor Company) not the regular stuff, and of all places
> >AutoZone
> >carries a high end line that holds up pretty good., Gold, part number is
> >DR2001G, sold as set only. .NAPA has two lines, red by Echlin, and blue by
> >standard. Echlin stay away from on GM, fine on Ford or Chrysler.
> >
> >Whitelightning
>
>
> Thanks, Whitelightning.
>
> Ignition control module is something I hadn't considiered. Can this be
> tested with a multimeter? If so, what numbers should I be looking for?
>
> Also, when testing current going into the coil, is it ~12V? Is it
> constant or intermittent?
>
> Any other thoughts on places to look would be greatly appreciated.
>
> -- Christian
Just get yourself a Haynes P# 24064 manual. It has all the
tests,illustrations,instructions for replacement etc. I don't see how
you could fix this truck without the manual,except by continuing to
throw $ at it and a lot of trial and error attempting to replace items
without instructions.
 >> Stay informed about: Testing Ignition Coil (1984 GMC 1500 Sierra Classic) 

On Thu, 10 Aug 2006 23:19:39 GMT, "Whitelightning"
<white.lightning2 DeleteThis @verizon.net> wrote:
>
>Future reference. The rotor can be visually inspected after removal,
>turn it over and look at the bottom side center, will look charred. Look
>for signs of "red dust" in the cap and on the distributor, This is caused
>by the spark shooting down through the rotor and arching off things, like
>the advance weights around
>their pivot pins..If there is a lot of it in there, the ignition module
>maybe damaged as well,
>and even the pick up coil for that matter.
> Don't buy cheap caps and rotors for GM. Stick with AC Delco,
>Standard Ignition, the Blue Streak line, (excuse me Standard Ignition is
>now Standard Motor Company) not the regular stuff, and of all places
>AutoZone
>carries a high end line that holds up pretty good., Gold, part number is
>DR2001G, sold as set only. .NAPA has two lines, red by Echlin, and blue by
>standard. Echlin stay away from on GM, fine on Ford or Chrysler.
>
>Whitelightning


Thanks, Whitelightning.

Ignition control module is something I hadn't considiered. Can this be
tested with a multimeter? If so, what numbers should I be looking for?

Also, when testing current going into the coil, is it ~12V? Is it
constant or intermittent?

Any other thoughts on places to look would be greatly appreciated.

-- Christian
 >> Stay informed about: Testing Ignition Coil (1984 GMC 1500 Sierra Classic) 

Or take it down to your parts store and they should have a machine to test
the modules.

Jape


"brianorion" <brianorion5 RemoveThis @msn.com> wrote in message
news:1155312815.768427.5290@m73g2000cwd.googlegroups.com...
> Just get yourself a Haynes P# 24064 manual. It has all the
> tests,illustrations,instructions for replacement etc. I don't see how
> you could fix this truck without the manual,except by continuing to
> throw $ at it and a lot of trial and error attempting to replace items
> without instructions.
 >> Stay informed about: Testing Ignition Coil (1984 GMC 1500 Sierra Classic) 

A few things...

First, you have what's called a "High Energy Ignition", most commonly
referred to as the "HEI".

There should be one wire coming in on the driver's side of the
distributor cap (2 wires if the truck has a tach). That's the 12vdc
"hot" wire that supplies power to the distributor. If you pull that
wire off, and turn the ignition to the "ON" position, you should get
12+ volts when testing the wire and ground.

If the ignition module was cooked to begin with, I doubt any further
damage was done while replacing the coil. But make sure that the
little metal strap (sometimes a very short wire) is connected from the
frame of the coil, and goes to what I believe (IIRC) the center leg of
the 3-pin connector that plugs into the module and capacitor. Without
that wire there, you'll cook every new ignition module immediately,
having never gotten the truck started.

I'd go ahead and look at the ignition module, and count the pins on it.
I don't know which year they went from the older 4-pin module to the
newer 5-pin module. The 5-pin version is what's on my '86 Chevy. The
5-pin version uses a very basic computer connected to the distributor
and a knock sensor, and it's sole purpose is to interupt (delay)
timing. It has been known to be problematic, to the point that GM
issued a service bulletin on modifying the system to render it
functionally the same as the older 4-pin version. I don't know to what
degree the computer can fail, or what the symptoms are, but it's worth
investigating. Bypassing it is as easy as jumpering two wires together
behind the glovebox. Search this group for my name as well as "ESC"
(electronic spark control) if you'd like to know more.

Provided that the wire supplying voltage is giving you 12v+ when the
key is "on", I'd say you're pretty much down to the ignition module, or
the little capacitor. If you end up replacing the module, get some
heat-sink grease, sometimes mistakenly referred to as dielectric grease
(something entirely different). The stuff you want is a thick, white
paste and the bottom of the ignition module needs a coat of the stuff
before you reinstall it back in the distributor.

Hope this helps, and as always, please report back regardless of
whether you fix it or not!

~jp

CMM wrote:
> He went ahead and replaced the coil and rotor. He's pretty much just
> throwing money at it, hoping something will work. Neither of those
> things did, unfortunately.
>
> The coil on this one is integrated and doesn't have a wire that feeds
> the diistrbutor. I'm going to have him check now the wires that feed
> the coil to see if they have power.
>
> -- Chrisitan
 >> Stay informed about: Testing Ignition Coil (1984 GMC 1500 Sierra Classic) 

I want to thank EVERYONE who helped me out with this. Your advice was
the key to solving this puzzle.

We hooked a light up to each side of the wires going into the coil.
With the other end of the test light grounded, the bulb lit up for
each side-- neither would flash with the engine turning over. NAPA
store tested the ignition control module and it was faulty. Put a new
one in and it's running like before.

-- Christian
 >> Stay informed about: Testing Ignition Coil (1984 GMC 1500 Sierra Classic)