Dies while driving, need advice. 90 Suburban 350TBI

[Wes Harden]

please check the fuse-able links at the starter, also make sure the battery cable at the starter is clean and tight. Fuse link provides power to the ignition switch, fuse block, head lamps, and horn.

If one of the fuse links is damaged, and providing reduced current flow or intermittent open you can create a stall/shut down condition by turning on a heavy electric load, ie head lamps, blower motor.
The grounds too, as @ktmoutfront mentioned, you need a ground to the radiator core support, the frame, the engine, and the firewall. The engine ground should to the block, at an unpainted spot on it's own bolt. Th exhaust manifolds are a no no, the alt bracket, while many do this hand have no issues, is not ideal. My batter to engine ground is on the intake manifold at front right corner. If your truck is a tbi there are some sensor and computer grounds on the t stat housing these get treated poorly over the years and need inspection, relocation.

 

[Wes Harden]

not my picture stolen from the web. A good example of where factory fuse links are located on our Squares. These appear to have been replaced at some point.

2nd stolen photo shows what a damaged link will look like. easiest way to test is grab one side near the plastic bead and pull, if it stretches it's bad.

 

[HankScorpio]

I would lean toward a bad connection also at this point. I have had battery terminals that looked fine but were corroded inside. I have also had cables that were corroded inside the insulation an inch or 2 down from the connections. The fact that it runs well and is charging correctly until a large voltage draw makes me think bad connection or corrosion.

 

[HankScorpio]

When you have a poor connection the little bit of conductor that is working gets overloaded when you draw too much power. A blower motor or starter could cause this easily. The arc that is caused by the overload breaks the connection and causes a little burnt spot that will not conduct electricity. When you check the connections and move wires around its probably making contact until it overloads again. Good chance you have touched or wiggled the problem area while troubleshooting since the power keeps coming back.

 

[Groz's Burb]

Thank you all, i will do some more troubleshooting tomorrow with your advice!

Side note:. My cables have this brown goo where they connect to battery terminals. Should i clean this off? I thought dielectric grease is normally clear

Thanks in advance y'all!

 

[Wes Harden]

yeah give'm a scrubbing with a wire brush battery too.

 

[dyeager535]

My dielectric grease is tan/brown colored. But pretty thin. That's probably old dielectric grease.

 

[Blue85]

Just an FYI if you don’t know, dielectric grease in an insulator. Do not get it on the portion where current flows between contacts.

Incorrect. If the contacts mate as intended, the grease will be displaced. It's function is to block air and moisture from outside from reaching the areas that can be corroded.

 

[dyeager535]

Exactly. It’s an insulator. Should not be used where the contact of current flow is. As you said “if they mate correctly” so don’t place the dielectric grease on the contact points. It’s fine to insulate or cover the area (top of battery terminal) but placing it on the the terminal and then attaching the battery cable is a no go.

Interesting discussion.

Also interesting very, very few say dielectric grease should be used on the conductors themselves. These guys test it and say otherwise:

Does Grease Affect Conductivity? | Nye Lubricants

Connector grease does not interfere with conductivity. Our test tutorials demonstrate the conductive and insulating properties of NyoGel® 760G.

www.nyelubricants.com

I don't know enough to see potential failures in their test methodology. I've been ignorantly slathering all my 12V electrical connections in dielectric grease for the past few years, and thus far have not experienced any issues doing so. But I could just be lucky. One thing I've been cognizant of is heat, and not using it where heat is going to be so bad as to melt/burn the stuff.

 

[HankScorpio]

I use the spray on my battery connections after they are hooked up. Slows down corrosion a lot.

 

[Blue85]

Exactly. It’s an insulator. Should not be used where the contact of current flow is. As you said “if they mate correctly” so don’t place the dielectric grease on the contact points. It’s fine to insulate or cover the area (top of battery terminal) but placing it on the the terminal and then attaching the battery cable is a no go.

It almost looks like you're agreeing with me, but we're still saying opposite things. If the terminals make contact without grease, they will still make contact with the grease. Just now all the parts that were in air are now covered. (Unless you have so much that you can't tighten the bolt or whatever.) Some factories lube connections during assembly (I've been in some). Sometimes it's to reduce insertion force, sometimes it reduces fretting/intermittent contact. Like the good old "horn grease" for the slip contacts in a steering column.

 

[scouthead]

wait, I was supposed to grease my horn????@!!

 

[Wes Harden]

Always @scouthead always

 

[scouthead]

Always @scouthead always