92 GMC troubleshooting

[Schurkey]

Electrolytic capacitors are the bane of electronics.

My "other" hobby--home theater with an emphasis on audio--involves occasional replacement of electrolytic caps. The biggest improvement I made to my stereo speakers was to scrap the ~20 year old electrolytic caps in favor of similar-value film capacitors. Unlike electrolytics, film capacitors don't have a "service life" as such. Downside is that they're more-bulky, and more-expensive. Electrolytics are cheap and compact.

 

[Anchor]

My pleasure, Anchor. I was fortunate to have mentors at critical junctures in
my career...and now it's my turn to pass along their guidance/pay it forward.

****

Alright. Your search for a map of the ECM wiring is over. Over HERE is a collection of
the Factory Service Manuals. You are in luck, for it looks like all the '92 Manuals are in
the collection. You should download these so that you can learn all about the GMT400
systems, documented by the people who designed and supported them.

To give you a quick taste of what you will find, here's a couple of pages from the
Electrical Wiring & Diagnostic manual, focusing on the ECM inputs & grounding:

You must be registered for see images attach

And here's looking at the Ground Distribution diagram -- essentially looking at the information above from the other side of the circuit:

You must be registered for see images attach

Finally, I've attached the Title Page of the manual I pulled the above from -- this just shows
you that the diagrams I'm sharing match the year of your vehicle.

****

I encourage you to take full advantage of these valuable technical resources,
for when it comes to all things having to do with mobility, the following is true:

"There is nothing more expensive than a lack of knowledge."

Best of luck in your journey towards self-sufficiency. And if you find
something in the manuals that you don't understand, just ask in here
and no doubt a member will help you sort it out in short order.

Cheers --

Who was that masked man? Seriously Road trip, thank you for your help and I appreciate that and your wit. How true the quote about lack of knowledge. Made me wince.

 

[Road Trip]

How true the quote about lack of knowledge. Made me wince.

I use that quote on myself every time I start to fatigue, get tired of
thinking, and instead want to make some progress and just throw a
popular parts choice at the problem du jour. :-(

Usually this quote (and a coffee break) is enough to motivate me to
gonkulate on the fix just a little bit more. Of course the corollary to the above
is waiting to take over: "Analysis leads to Paralysis." :0)

****

Sometimes quality troubleshooting is a like finding yourself on a tightrope.
(Tip of the hat to Leon Russell. :0) Been troubleshooting my entire adult
life...but still consider myself a student of the craft. And I find that watching
others in this forum troubleshoot is a way better use of my time than just
about anything on the telly, no matter how many channels there are to
choose from.

What can I say? So much more to learn than there is time left to do so.

Cheers --

 

[Anchor]

I use that quote on myself every time I start to fatigue, get tired of
thinking, and instead want to make some progress and just throw a
popular parts choice at the problem du jour. :-(

Usually this quote (and a coffee break) is enough to motivate me to
gonkulate on the fix just a little bit more. Of course the corollary to the above
is waiting to take over: "Analysis leads to Paralysis." :0)

****

Sometimes quality troubleshooting is a like finding yourself on a tightrope.
(Tip of the hat to Leon Russell. :0) Been troubleshooting my entire adult
life...but still consider myself a student of the craft. And I find that watching
others in this forum troubleshoot is a way better use of my time than just
about anything on the telly, no matter how many channels there are to
choose from.

What can I say? So much more to learn than there is time left to do so.

Cheers --

Now that I put in a working temp sensor and fixed the map it feels good to hear it run. Still struggling though. Last eve I was running the truck in the shop and reached under the hood and goosed the throttle a few times up to maybe 2500 rpm's. I was leaning over the alternator when I did so and some small particles were flying up and hitting my face. The only thing I could think of was that they were flying out of alternator. Next thing you know I am reading about diode bridges breaking down and all of the possible symptoms of ac current flowing through the electronics. I hope you teach some automotive classes as I think you might be able to motivate some to excel. I dream of the day I can do my happy dance on this project. I will certainly post my results when that happens.

 

[Schurkey]

goosed the throttle a few times up to maybe 2500 rpm's. I was leaning over the alternator when I did so and some small particles were flying up and hitting my face. The only thing I could think of was that they were flying out of alternator.

Wild guess with no evidence: Alternator had dust built-up inside, revving the engine promoted the dust clumps to fly off of the internals and out with the cooling airflow.

Connect a multimeter to the + output terminal and the grounded alternator case. Set the multimeter to AC voltage, on (most likely) it's lowest scale. Verify that there's extremely little AC "ripple" on the alternator output. (There is always some AC ripple.)

 

[Anchor]

Wild guess with no evidence: Alternator had dust built-up inside, revving the engine promoted the dust clumps to fly off of the internals and out with the cooling airflow.

Connect a multimeter to the + output terminal and the grounded alternator case. Set the multimeter to AC voltage, on (most likely) it's lowest scale. Verify that there's extremely little AC "ripple" on the alternator output. (There is always some AC ripple.)

Thanks. Will check further in am.

 

[Anchor]

My pleasure, Anchor. I was fortunate to have solid mentors at critical junctures in
my career...and now it's my turn to pass along their guidance/pay it forward.

****

Alright. Your search for a map of the ECM wiring is over. Over HERE is a collection of
the Factory Service Manuals. You are in luck, for it looks like all the '92 Manuals are in
the collection. You should download these so that you can learn all about the GMT400
systems, documented by the people who designed and supported them.

To give you a quick taste of what you will find, here's a couple of pages from the
Electrical Wiring & Diagnostic manual, focusing on the ECM inputs & grounding:

You must be registered for see images attach

And here's looking at the Ground Distribution diagram -- essentially looking at the information above from the other side of the circuit:

You must be registered for see images attach

Finally, I've attached the Title Page of the manual I pulled the above from -- this just shows
you that the diagrams I'm sharing match the year of your vehicle.

****

I encourage you to take full advantage of these valuable technical resources,
for when it comes to all things having to do with mobility, the following is true:

"There is nothing more expensive than a lack of knowledge."

Best of luck in your journey towards GMT400 self-sufficiency. And if you find
something in the manuals that you don't understand, just ask in here
and no doubt a member will help you sort it out in short order.

Cheers --

Thanks Again; I was just looking back through here and saw I had not responded to your last message. I appreciate your knowledge as well as your wit.