TRUCK IS ACTING CRAZY

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thinger2

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Thank you I will try and find a spot on the head to mount the ground to.
I used that bracket on mine because Im old and beat up and aint no way in hell that I can do it.
Any place you can get a good solid rust free clean bolt up on that head will work just fine.
It doesnt matter where it grounds onto that head.
It just has to have a good clean solid ground to that head.
And the same thing applies to your intake grounds.
TBI systems are very voltage sensitive.
They function in a fairly narrow set of parrameters.
A TBI will not work with the ecu untill you fix the broken stuff that is beyond the range of the
 

thinger2

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If you changed the ground from the head from firewall to frame that can cause a ground loop that ultimately will cause a Ground Plane issue and could lead to a fire.
changing a ground wont lead to a fire.
Only a short to ground or hot to another component or an overheated wire with something combustable will do that.
Altering or moving a ground on a TBI without a really solid plan leads to performance problems and random hard to diagnose performance issues.
And those issues tend to accumulate over time.
Bad grounds rot less noble metals.
The grounds are in place for reason
Amd it sure as hell isnt some kind of GM generousity.
When you look at anything built by any American manufacturer in the 90s you need to understand that whatever they put into the build is the bare minimum.
And that is your battery cables and your relays and the fuses and all of the contacts in the relays etc..
The tailshaft on your transmission.
You cant bypass that minimum.
You can inprove on it.
But only by adding grounds.
Removing grounds from factory grounded systems is a recipe for chasing your tail.
 

1998_K1500_Sub

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Basically, grounds need to stay attached the the same "ground plane" as they were originally.
In other words, the same chunk of cast iron in your case.
If you move that ground off of the head to the block.
That ground now has to go through the head gasket.
It wont do that. It will ground to the shortest path.
The only way it can achieve that original grounding is through the head bolts.

So it sounds like you want to avoid passing current through the head bolts. If they (heads / bolts / block) were dissimilar metals, I would buy the argument sooner. For aluminum heads... it might be an issue in the long-term.

GM for years has grounded the battery to the block, at least on the iron-head engines I've seen. The battery charging current goes from the alternator to the head, the bolts, the block, to the battery. GM evidently is OK with this.

The problem people run into is that they do a continuaty test on the ground and get a tone out of the voltmeter and think its all good.

Most people don't have the experience or the knowledge base to know better.

Some talk without thinking.

Each ground serves a specific set of paths.

When you move a ground to a different plane, you change that"path"
That path will be the shortest most direct.

Hence the reason for a "star" ground. Eliminate the undesired paths from being in the conducting path.


And it will go through the easiest most conductive material.
Which can end up being the main bearings.

Yup. That's why one should stick with the OE ground arrangement.


Bad or improper or missing grounds can also eat the bearings out of your transmission.
They are grounded in those planes for a reason.

A "ground plane" actually has a formal definition if you happen to look.
 
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1998_K1500_Sub

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Sure. All grounds bolted to the head need to stay bolted to that head.
All things grounded to the intake need to stay grounded to the intake.
All things grounded to the block need to stay grounded to the block
All things grounded to the transmission need to stay grounded to the transmission.

Sounds like sage advice. It jibes with what I mentioned prior: "Don’t change the OE grounding plan."

But I'll allow for moving the ground strap from the head to the block on an iron head engine. GM for years has grounded the battery to the block, so the alternator charging current goes from the head to the block to the battery. There's no evident concern in this case.
 
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1998_K1500_Sub

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Removing grounds from factory grounded systems is a recipe for chasing your tail.

Yup. Bad idea.

You can inprove on it.
But only by adding grounds.

Adding them can introduce multiple ground paths if not done carefully. Better to avoid adding grounds unless you really (and I mean really) know what you're doing. Otherwise you'll wind up with the problem you cited (I quote):

"...you change that path. That path will be the shortest most direct"

and that's when bad things happen. You cited many examples.

Removing grounds from factory grounded systems is a recipe for chasing your tail.

Amen.
 
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thinger2

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N
Mechanic I used said it didn’t matter if it’s on the frame, & I’ve had no issues in the year since. Before I put new ground cables, both were broken & gave me no issues for years. When I had my engine replaced the mechanic at the dealer put ground from the block to the frame, but it was a dinky wire that I had replaced with a better one.
Your mechanic doesnt understand obd1 gm tbi.
Which is no big surprise at all..
An anceint rather short lived tech that never got passed on because of the microfiche to early document scanning transition to document imaging storage
A lot of mid 90s tech and its documentation is lost.
There was this big rush to digitize everything back then.
And they did.
And it was all done in feeble rapidly deteriorating formats that are essentially unreadable now.
We have the disks and the drives.
We just dont have a way to read them.
I can barely figure out how my friggen phone works.
I have no idea what any of you young people are talking about when it comes to computers.
None.
But I am probably one of the last people left who can program a tape reader Fanuc controller in HPGL or DXF and Im sure as hell the last guy who can run Prippet for Strippets
Since I stole the last copy of it
And the only reason that that is worthy of note is because we have some old aircraft and they need parts.
And now everybody is ancient or dead.
I know this has nothing to do with anything but Im rolling so Im gonna tell a story anyway.
Back not so long ago, back in the mid 90s.
We were all masters of our craft.
Aerospace prototype mechanics.
A guild of talented professionals.
And we built some crazy ****.
MX missiles , Tank armor, Bullitt proof cockpits.
We flew airplanes into mountains just to see what happened to them.

We shot frozen turkeys into a running ge jet turbine

And all of that is gone.
All of that generational knowledge and skill is gone.
What a lucky man I am.
To be in the right place at the right time and be smart enough to shut up and soak it all in
Thats my rant



If you changed the ground from the head from firewall to frame that can cause a ground loop that ultimately will cause a Ground Plane issue and could lead to a fireo
 

1998_K1500_Sub

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@thinger2, I've got a question for you.

What's your thought on the practice of mounting the ignition coil on the intake manifold? As I'm sure you're aware, the return current from the plugs to the coil passes from the heads to the intake.

It's an old practice on land vehicles and "time tested" there, but I've wondered if it would be considered poor practice on a ship or aircraft.
 

DerekTheGreat

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no I did all kinds repairs on it last summer and it does this nonsense. I will take the 1970's era over these any day. I don't know yet where that ECM OR ECU is but when I find it I'm throwing it in the street where it belongs. Ive had this truck for 10 years.
..So in case you get to that point, I'll take that truck off your hands. :) I love TBI, it's pretty stupid simple and reliable as a result. It's just craptastic parts (as others have mentioned) which cause you to pull your hair out in frustration. Last thing you should check is your coil. I was taught those things either work or they don't. Guess my instructor was talking about the type in my old '69 Plymouth. Well, my truck used to eat an ignition control module every seven to fourteen months or so. I cleaned all the grounds and just chalked it up to craptastic aftermarket garbage. Which it probably was, buut my truck always had one other issue: Upon start up it the tach would flutter a bit. Mind you this is an '89 that had moonies but I did the needle swap to. At some point I studied the electrical troubleshooting manual from GM for that truck. I remember reading something about how the tach signal comes straight from the coil and that the ECM uses that signal to fire the injectors (also already mentioned). I tested the coil per the test procedure in the manual and it tested OK. "Alright, so that's not my problem." I dealt with the flutter for another year or so. Then on a whim and with nothing to do, I swapped out that coil for a different one anyway. No more tach flutter and I think I'm pushing fourteen or fifteen months on the Standard Motor Products ICM with no failure yet.. So the synopsis is even though my coil tested ok, it was still bad.
 

PlayingWithTBI

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So the synopsis is even though my coil tested ok, it was still bad.
Yep, a bad coil can most certainly take out an ICM. I had a Pertronix Flame Thrower coil which went bad in ~2000 miles. The ICM went bad about the same time. The truck still ran but, once warm it'd stumble while cruising at ~2000 RPM. I replaced the ICM with an ACDELCO D1984A but, I still had a stumble at idle. I sprayed water on the coil (not the wires) and the engine almost died. Upon further investigation, it appeared the coil was shorting to the iron frame. No Ohm meter would find this, unless you use a Megohm meter which will shoot a high voltage spike through the windings and look for resistance to ground. Anyway I replaced the coil and have been stumble free for 2 years now :waytogo:

Look at the burnt spots at the coil and iron.
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DerekTheGreat

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It was throwing flame alright haha. I wonder if that's what mine was doing, I never sprayed it with water. Are they supposed to ground to the intake in some way? The bolts which held my coil in place were pretty corroded. So that could've been my issue or part of it.
 
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