Starter blowing fuses.

[sgms18]

I'm going to start from the very beginning. When I bought my truck ( m1028 ) the starter relay had stuck on & burnt the fusible link on the firewall. For whatever reason instead of fixing it the previous owner rigged up a push button straight off the battery post to the starter solenoid. No fuse or nothing just 2 wires & a button. I disconnected all that, replaced the burnt up relay with a standard 40a 12v relay. I know it's a 24v solenoid but the switching side is 12v & it works. I cut the stock connector off, wire up the pigtail for the new relay & added an in line fuse to the red wire that supplies 24v to the relay. My logic being if the relay or solenoid sticks again it would pop the fuse before it burnt the fusible link. I put it all together & it works perfectly. I put an app clamp on the ignition wire & it was pulling about 12a so I put a 15a fuse in it & it was fine for bout 6-8 months. Then one day I went to start the truck & it blew the fuse. I didn't have another 15 on hand so I stuck a 20 in it & was fine for several months more. I decided I was guna drive it to work one morning & again it blew the fuse soon as I turned the key. Since then it blows 95% of the time when but occasionally you can start it a time or two. When it works it works perfectly, spins over good, starts right up & runs fine. I've checked for shorts in the wiring & found nothing. I can disconnect the ignition wire from the solenoid (no load) & it won't blow the fuse, relay clicks on & off as it should. Thought maybe it was a bad solenoid so I pulled the starter, swapped the solenoid from another old starter I had laying around. Reinstalled, same thing. Pulled the starter again & replaced with a whole new starter, same thing. Thought maybe I had a weak battery & low voltage was causing a high amp draw. I had both batteries load tested & sure enough one was bad. Replaced both batteries just so I got 2 new ones the same age. She fired up 2-3 times & I thought I finally had it licked then the next day pop goes the fuse again. I disconnected the ignition wire from the starter & ran a jumper wire w/inline fuse from the solenoid straight to the battery post & it still blows the fuse totally independent from the trucks wiring. What the hell is going on. I've been chasing my tail for months. Any ideas?

 

[SomeNewGuy]

I honetly dont know much, but I do know there are 2 posts on my solenoid for the relay. One is labeled I think B and the other S. (Outer post/Inner post) are you connected to the one labeled S, or the inside one? Is the fat wire connected to the bottom post? Is the post at the nose of the starter connected to the bracket? (If I remember correctly this is part of the ground for the unit)

Outside of this, not sure...

 

[Squibbly]

My brother @Rocknus had a similar issue with his truck. In fact, there was evidence that it had lit the dash on fire at one point.
He went through all the wiring in a video.

I think at this point in the video he just tells you what *he* found, but you may want to watch the whole thing, in case it's one of the other things he tried before he found the actual cause.

 

[sgms18]

Of the 3 starters I have around here none have 2 small post. Just one big post for the battery cable & 1 small post for the ignition wire. I know it's hooked up right cause it worked for months before this problem popped up.
Now watching that video I noticed the ground cable from his battery goes to the body and the alternator bracket. Mine goes to the body and to the junction block on the firewall and another cable from the junction block to the back of the intake manifold. I don't think it matters. Correct me if I'm wrong.

 

[sgms18]

Well, the more I mess w/this thing the weirder it gets. I just disconnected the negative battery cable & the starter is still hot. How is that even possible?

 

[Squibbly]

Of the 3 starters I have around here none have 2 small post. Just one big post for the battery cable & 1 small post for the ignition wire. I know it's hooked up right cause it worked for months before this problem popped up.
Now watching that video I noticed the ground cable from his battery goes to the body and the alternator bracket. Mine goes to the body and to the junction block on the firewall and another cable from the junction block to the back of the intake manifold. I don't think it matters. Correct me if I'm wrong.

All of your grounds need to be clean. Assuming you have a 24v starter there needs to be 24v at the wire when cranking. Believe me when I tell you, “it was working” means nothing in these trucks. Mine was working with almost no CCA left in either battery, no functioning glow plugs, a loose starter, a ground down flywheel, the wrong torque converter, the parking pawl bracket on backwards, no oil, wrong glow plug relay, bad grounds, and live wires hanging and touching the engine block. They have a lot of room for forgiveness, until they don’t.

 

[Squibbly]

Well, the more I mess w/this thing the weirder it gets. I just disconnected the negative battery cable & the starter is still hot. How is that even possible?

Sound like Scooby found a clue.

Although now that I think about it, your mounting bracket is grounded..

 

[SomeNewGuy]

Sound like Scooby found a clue.
View attachment 854691
Although now that I think about it, your mounting bracket is grounded..

This.
The post at the front is shown as ground in the schematics. There should be a post on the bottom of the starter solenoid that has a strap leading to the front and going inside of the starter. From there ground goes into that post that hooks to the mounting bracket.

The ground wires leading to intake manifold is just... weird...

Edit:
289-34 , E-3 , PG 946
No ground wires shown.

 

[Squibbly]

This.
The post at the front is shown as ground in the schematics. There should be a post on the bottom of the starter solenoid that has a strap leading to the front and going inside of the starter. From there ground goes into that post that hooks to the mounting bracket.

The ground wires leading to intake manifold is just... weird...

Edit:
289-34 , E-3 , PG 946
No ground wires shown.

It really sounds like his second battery is grounded. Electricity needs a circuit, and the hub is the battery.
What happens if you pull both wires off the first battery? Still voltage going to the starter?

If so, someone may have stuck a grounded wire onto the 12V block near the GP relay on the firewall.


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[sgms18]

What is this between the pos & neg junction blocks & how is not a dead short? Sorry if I'm asking stupid questions. Admittedly electricity is not my strong point.

 

[Squibbly]

What is this between the pos & neg junction blocks & how is not a dead short? Sorry if I'm asking stupid questions. Admittedly electricity is not my strong point.

It's a capacitor. #5 in the photo below from page 115 of the -34P Manual.



FYI, if you don't plan on running military radios, you can pull it off, and sell it on ebay for 29.00 like Hillbilly Wizard, although his sticker alone is worth $29.

CUCV Capacitor for distribution block for firewall | eBay

 

[ezgn]

My brother @Rocknus had a similar issue with his truck. In fact, there was evidence that it had lit the dash on fire at one point.
He went through all the wiring in a video.

I think at this point in the video he just tells you what *he* found, but you may want to watch the whole thing, in case it's one of the other things he tried before he found the actual cause.

Man, I didn't know Rocknus is your brother. I started watching his videos a while back. I watched one where he tore down a 6.2 but never found the part where he put it back together. The dude is a cool warrior. Good brother to have.

 

[Squibbly]

Man, I didn't know Rocknus is your brother. I started watching his videos a while back. I watched one where he tore down a 6.2 but never found the part where he put it back together. The dude is a cool warrior. Good brother to have.

He’s still planning on doing the video. A lot happened between then and now that delayed the build, but I think he’ll probably finish it up in the spring.


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[ezgn]

He’s still planning on doing the video. A lot happened between then and now that delayed the build, but I think he’ll probably finish it up in the spring.


Sent from my iPhone using Tapatalk

I am looking forward to it, and Mr. Hamerstien!

 

[sgms18]

Ok I took that capacitor off just to see if it made any difference & it did not. Didn't really expect it to, just ruling things out. Looked over the wiring again, didn't see any bad spots. I took the starter off AGAIN & tested it and another starter I got on hand off the truck. Both starters solenoids engage for just a second then trip the 30a circuit breaker in my power Probe totally independent of the truck. This is what made me look at the batteries. Like I said I duno much bout electrical stuff but I do know low voltage causes high amperage. I replaced both batteries w/Interstate remains 3-4 days ago. Still got the same issue.

 

[sgms18]

I tried to post a video of the starters tripping the circuit breaker in my power Probe but it said the file was too large.

 

[sgms18]

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[Squibbly]

Can you get two sets of jumper cables, disconnect the batteries from the truck and just run them in a series off the jumper cables to test this, or alternatively, make sure the truck isn't connected in any way to the batteries.
Simply trying to eliminate the truck itself from the equation, and bad wiring, or bad grounds, etc which could draw more amperage.

Also, if they are using a fusible link for this system (per design) and not an actual fuse it may be because the amp draw is variable and may go to more than 30 amps at times, so they use a "slower" fuse in the fusible link to accommodate this, whereas a fuse is just going to pop and that's it. What if you used one of these in your circuit? Amazon.com: Littelfuse MAX30BP MAXI Slo-Blo 299 Series Automotive Blade Fuse : Automotive

 

[SomeNewGuy]

In line with that, is your engine and fuel water filter grounded? Maybe bad ground at starter relay?

 

[sgms18]

Can you get two sets of jumper cables, disconnect the batteries from the truck and just run them in a series off the jumper cables to test this, or alternatively, make sure the truck isn't connected in any way to the batteries.
Simply trying to eliminate the truck itself from the equation, and bad wiring, or bad grounds, etc which could draw more amperage.

Also, if they are using a fusible link for this system (per design) and not an actual fuse it may be because the amp draw is variable and may go to more than 30 amps at times, so they use a "slower" fuse in the fusible link to accommodate this, whereas a fuse is just going to pop and that's it. What if you used one of these in your circuit? Amazon.com: Littelfuse MAX30BP MAXI Slo-Blo 299 Series Automotive Blade Fuse : Automotive

The slo-blo fuse is interesting. I've never seen those before. The wire that feeds 24v to the starter relay dose originate from a fusible link at the junction block. Maybe it was a bad idea adding another fuse just before the relay. But.... before I pulled the starter I ran a jumper straight from the battery post to the starter solenoid. Originally I had an inline fuse in the jumper. Once it blew I cut the fuse out & touched the unfused wire to the battery post quickly. It arced & stuck to post instantly. The solenoid clicked but the starter didn't spin the engine over. I did all this w/the ignition wire from the truck disconnected. I'll try the jumper cables thing soon as I get a chance. That's a good idea.