Grounding Problem

[BigRandy]

My 74 C-10 has an odd problem - odd to me anyway.

Battery has 13+ volts. Cables are clean and tight.

It will usually start fine but sometimes cranks like the battery is weak when it isn't, and the #10 wire from the battery gets smoking hot which tells me it's trying to use that as ground.

The #10 ground wire on the neg post is bolted to the frame which I'm guessing is normal. The 2ga negative cable is bolted to the alternator bracket. Connections have been checked and cleaned. The 2ga cable looks great.

I removed and cleaned the braided strap from the motor to the firewall. Anything else I can check?

I thought bout running another 2ga wire from the alternator bracket to the frame next to the #10. That should give the motor and frame enough ground to work but that isn't the right way to fix it. It's got me puzzled - the starter is bolted to the motor which is grounded at the alt bracket. That should be enough but I think I'm missing something.

Thanks!

[hatzie]

The ground cable could be corroded off inside the jacket. Look for bubbles and other imperfections in the wire jacket.

Do a voltage drop test.
Set your digital meter to the DC range just over 14V.
Check the voltage directly at the battery.
Keep the positive meter terminal attached to the positive battery terminal.
Move the negative meter terminal to the battery cable lug on the battery. Is it still reading within .1VDC of the battery test voltage? NO means the battery terminal needs to be cleaned as well as the battery post or side lug.
Move the Negative meter terminal to the Crimped-on battery cable ring terminal that's bolted to the alternator bracket. Is the voltage within .1VDC of Battery voltage? NO? The cable is bad.
Move the negative meter terminal to the alternator bracket. Is the voltage within .1VDC of Battery voltage? NO? Add a star washer under the ring terminal and torque the bolt back down. Then re-test.
Move the negative meter terminal to the intake manifold. Is the voltage within .1VDC of Battery voltage? NO? Add star washers under the alternator bracket mounting bolts and re-test.

[andyh1956]

Yeah I think hatzie is correct, you gotta bad ground cable.
for a quick test, hook one lead of your jumper cables up from the engine to the neg batt term & crank the engine several times. That should tell you right off it it's a cable problem.

[BigRandy]

Oh wow I feel dumb. I know to check VD but didn't even think about it. I checked continuity and all grounding points for corrosion or missing star washers but never considered a voltage drop test. (Notice I didn't abbreviate "voltage drop" since it was in front of "test." Didn't sound right.)

I have no idea why I skipped that but I'll check and reply. Thanks for the info!

[homemade87]

As said above , could be a bad cable .

I do not like putting a ground cable to a alt for the main starter wire. The circuit has the pass thru the alt to the bracket and from the bracket to the block . Those mounting points get corroded and looses it ability to pass thru .

I would move the ground from the alt to the block first to see if this is you issue . If this does not fix it most likely the wire .

[hatzie]

Originally Posted by BigRandy

Oh wow I feel dumb. I know to check VD but didn't even think about it. I checked continuity and all grounding points for corrosion or missing star washers but never considered a voltage drop test. (Notice I didn't abbreviate "voltage drop" since it was in front of "test." Didn't sound right.)

I have no idea why I skipped that but I'll check and reply. Thanks for the info!

Ahh yes. CRS. It doesn't get better with age.

[andyh1956]

Be sure to check for corrosion between the starter nose & the mounting ear on the block.
That ferrous / non ferrous thing you know...

[BigRandy]

Originally Posted by andyh1956

Be sure to check for corrosion between the starter nose & the mounting ear on the block.
That ferrous / non ferrous thing you know...

I put a reman starter on it about 5 months ago. Been working fine and spins the motor like mad - most of the time. I thought first it might be the starter but the small ground is getting hot leading me to believe it's a bad ground elsewhere. Didn't get a chance to check for the voltage drop today. Busy painting the house. May get to it tomorrow if I get done with the house. Will check the starter while I'm at it. Good info! Many thanks.

[andyh1956]

Originally Posted by BigRandy

I put a reman starter on it about 5 months ago. Been working fine and spins the motor like mad - most of the time. I thought first it might be the starter but the small ground is getting hot leading me to believe it's a bad ground elsewhere. Didn't get a chance to check for the voltage drop today. Busy painting the house. May get to it tomorrow if I get done with the house. Will check the starter while I'm at it. Good info! Many thanks.

Glad to see you got your priorities straight.
Get them "Honey dos" done 1st, that truck can wait!

[BigRandy]

Originally Posted by andyh1956

Glad to see you got your priorities straight.
Get them "Honey dos" done 1st, that truck can wait!

The truck, paint ,honey-do's and anything else that might require shoes and a coat will be on hold at least until Thursday. Freezing rain is on the way.I'm ready though. Took the truck out this afternoon to get enough tacos and beer to last a couple days and it ran great but I didn't shut it off.

I don't know why I like that old truck so much. I have an F150 with 36K in the garage but prefer to drive that rusty, dented, rumbling gas hog every chance I get.

[SCOTI]

Changing the factory ground set-up is one of my first upgrades.

I change the ground from the NEG batt terminal to the alt bracket. I always move it to the frame & run a second ground cable from the same spot of the frame over to the engine block vs the alt bracket After that, I verified there was a ground strap to the cab (so many times during engine swaps these are not reconnected).

On my dually, each frame rail is grounded to each side of the engine block & again to the cab on each side.

[hatzie]

Originally Posted by SCOTI

Changing the factory ground set-up is one of my first upgrades.

I change the ground from the NEG batt terminal to the alt bracket. I always move it to the frame & run a second ground cable from the same spot of the frame over to the engine block vs the alt bracket After that, I verified there was a ground strap to the cab (so many times during engine swaps these are not reconnected).

On my dually, each frame rail is grounded to each side of the engine block & again to the cab on each side.

The motor mounts are a good place to connect the block grounds on the diesels.

[BigRandy]

Okay.... I found a a new ground wire to add as a second but while waiting for it to arrive I picked up one of those twist type battery brushes and gave the posts and terminals a good scrubbing. Also buffed the alt and frame where the negative cables attach and so far it's been fine.

I know that all seems simple and should have been the first thing to check but to be honest they looked clean and there was no corrosion, and the neg cable to the alt bracket had a star washer and continuity was confirmed - just not the voltage drop. . It looked good but now I know for certain it is. One thing I failed to mention was the dielectric grease I put on the terminals. I may have gotten some on the inside of the terminals but if I did it wasn't obvious when I was cleaning them with the brush. If so then it's gone now.

Since the problem is or was intermittent I'm not convinced it's fixed so I am keeping a set of cables and a digital MM with me and will check the voltage drop if it happens again. Holding off on adding the second ground for now.

I appreciate the advice and help. Thanks.

[andyh1956]

When I was in MRAP school at Red River Army depot during a trouble shooting class the instructor had put electric tape around one post on a battery. I kept checking for voltage there but was probing the post & NOT the cable terminal! I knew I had voltage but couldn't figure out what was wrong! Or why the instructors were laughing at me!
A truck that has given a problem starting can never quite be trusted 100% again, you always wonder if or when it will let you down.
Kinda like your pistol. Mine's never failed to go bang but what will it do when your life depends on that bang?
If it's ever hiccupped you will always wonder...

[andyh1956]

Originally Posted by SCOTI

Changing the factory ground set-up is one of my first upgrades.

I change the ground from the NEG batt terminal to the alt bracket. I always move it to the frame & run a second ground cable from the same spot of the frame over to the engine block vs the alt bracket After that, I verified there was a ground strap to the cab (so many times during engine swaps these are not reconnected).

On my dually, each frame rail is grounded to each side of the engine block & again to the cab on each side.

You remember when the ground cable had an eye terminal in the Middle & grounded to the frame & then jumped over to the engine?

[BigRandy]

Originally Posted by andyh1956

You remember when the ground cable had an eye terminal in the Middle & grounded to the frame & then jumped over to the engine?

I don't remember an eye in the middle but I think I remember when they grounded to the frame and the engine was grounded to the body with a strap - I think.

[BigRandy]

Originally Posted by andyh1956

When I was in MRAP school at Red River Army depot during a trouble shooting class the instructor had put electric tape around one post on a battery. I kept checking for voltage there but was probing the post & NOT the cable terminal! I knew I had voltage but couldn't figure out what was wrong! Or why the instructors were laughing at me!
A truck that has given a problem starting can never quite be trusted 100% again, you always wonder if or when it will let you down.
Kinda like your pistol. Mine's never failed to go bang but what will it do when your life depends on that bang?
If it's ever hiccupped you will always wonder...

I know the feeling. I have had a .40 S&W for almost 20 years. Never had a jam or FTF but if I did it would probably be gone. It's hard to get the trust back.

I'll probably end up running a second ground from the engine to the frame anyway just so I can feel better about it. The reason I didn't do that already is because it *should* be good without it as long as everything works the way it was designed.

[franken]

The large battery cables have exactly one purpose and that's to run the starter. The big ground cable should go to the block first. I like the old motor mount bolt hole at the front of the block by the timing cover.

[BigRandy]

Originally Posted by franken

The large battery cables have exactly one purpose and that's to run the starter. The big ground cable should go to the block first. I like the old motor mount bolt hole at the front of the block by the timing cover.

That's easy enough. I'll move it and see. I want it to work as per the OEM method, but it's 44 years old and being practical is more important than being original. Even more so if I'm on the road somewhere and it decides to crap out.

[Dayton601]

You got me to thinking about my starter issue I had a few weeks ago, the motor would start fine when cold, would drive it to town, go into the store or something and would turn it off, when i tried to start it again, it would engage but act like the battery was dead and not engage fully, it would jerk and clatter and only turn over a few times, then nothing, I would let it sit a few minutes and it would start, went and bought a new gel cell battery, ran it a few times and let it sit a few days, it started fine, until I drove it to town and it started the ole hard to start thing again, I had recently put a new starter on it, so that didn't cross my mind, then the next day i came out and it wouldn't start, after checking the battery and the cables, i found the starter wire from the switch to the solenoid was barely loose, I guess when the starter got hot from running it would not let enough voltage go through the wire to engage the starter properly, most likely nothing to do with yours, but you did mention you changed your starter out a few months back, so I'm just throwing it out there,

[SCOTI]

Originally Posted by BigRandy

That's easy enough. I'll move it and see. I want it to work as per the OEM method, but it's 44 years old and being practical is more important than being original. Even more so if I'm on the road somewhere and it decides to crap out.

Just because the factory did it a certain way doesn't mean it was the best way. Functional? Yes, but they did things w/a 'cost effective' mind-set. I do the main cables the same size (usually 1GA & made to spec) then do my secondary grounds w/4GA pre-made battery cables available @ most parts stores. Overkill? Yep. But I don't have starting or ground issues either.

[BigRandy]

Final update time.

No problem for a month or so until today. As always it starts fine 1 out of 100 times and the one time it doesn't it will smoke the #12 ground from the neg post to the core support.

Today when it did it I used my volt meter and found the same voltage at the motor as I did between the posts. I even checked the starter just to rule it out. Battery cables and terminals were tight and clean - no buildup or corrosion on or between the surfaces.

I had to be overthinking this so again I went back to the neg cable that I had bolted to the block and pulled the ends to see if they might be loose, even just a little. No go. The terminals didn't budge. But what if old age caused corrosion (mentioned in here) on the inside that I couldn't see? The VD had always been zero everywhere but why won't it pass current? The twister for me was that it wasn't repeatable. One time it won't start and 2 minutes later it fires up like new.

With the neg cable in my hands I checked the resistance with my multi meter and there it was. Depending on how I held it the resistance was all over the scale. It's 100% bad but still looks good enough to wipe down and sell as NOS.

Then it hit me. Crap. You dumb #%&#!

I had been checking voltage drops with the #12 wire still attached to the neg battery post, which explains why I had good volts everywhere but weak amps.

So I replaced the neg cable and now that 454 spins faster than it has in the 8 months that I've owned it.

There's no arguing with the findings so I'm 99% sure it's fixed now. Thanks for the tips and suggestions. They came in handy.

I grew up on a farm and worked around a fair amount of machinery in my life. I've seen busted batteries, posts burnt down, cabled chewed, burnt and cut but I have never seen a 34" piece of cable look new but work intermittently. They worked or they didn't, and when they didn't the reason was always obvious.

[Jeepwm69]

Good info here. I have a truck that does what Dayton601 described. I've suspected a bad cable but don't drive the truck often so haven't really put much effort into finding the problem.

[BigRandy]

Originally Posted by Jeepwm69

Good info here. I have a truck that does what Dayton601 described. I've suspected a bad cable but don't drive the truck often so haven't really put much effort into finding the problem.

Yep. Wondered about that myself when I read his reply. I was the one who put that stater on a few months ago and remembered very well that I tightened the snot out of everything when it went in. On the off chance that it might not be making good contact with the block I had to rule that out so I did. Everything was just as I left it.

I was a little disappointed that I trusted my eyes and not my brain. I know very well that electricity always takes the path of least resistance but looking at the neg battery cable fooled the hell out of me. It was clean, ends were perfectly secure and bolted to the post and engine as direct as possible. I even knocked the paint off with a wire wheel so it had to be right, right? Wrong!

There's no way I could have found this without using the DMM. Wish I had a pic to show because when wiped clean it looks 100% as good as the new one.

I need to remember that I have tools for a reason.