Ground hopping my LDS - last questions - starter

[cattlerepairman]

Ground hopping my LDS - starter hookup issue

Almost there...
- want to hook up the tranny as well to test as a unit
- front engine mount and radiator mounted (no fan)
- will fill with water and Cascade for first run
- John Deere break-in oil 10W-30 standing by


Jumping the starter - here is where I would appreciate a look by more experienced guys/gals:

My plan (see image) is to use jumper cables as indicated and a big a** isolated screwdriver (or a jumper cable) between the two terminals on the starter solenoid:



Can you please confirm that this will result in the starter engaging and spinning the engine over? 2x12V truck batteries carry a lot of punch, the starter pulls a lot of amperage and I dont want to fry anything (including myself).

 

[quarkz]

Yep that is the way.

Ground to the engine block or the case of the starter motor.

If worried you could always unbolt the starter from the engine, and test your wiring with the starter laying on the on the ground.
Being held down by your foot, or a cinder-block.

But usual way is to place the screwdriver up & down between the posts, tip touching the +24, and then rock your screwdriver so it bridges those two post.
And you just tap it. A quick touch to see how it jumps, then go for holding across the posts for a "one, two" count.

You are going to hear and feel the bendix solenoid pop out, then the starter spin.

 

[pigpen60]

Ok I must know, why the cascade?

 

[gimpyrobb]

Ok I must know, why the cascade?

It is a non-sudsing cleaner to remove crap from the cooling system. If you used Dawn dish soap, you'd have a foam factory!

 

[m109a2]

Cascade uh,Nice tip to know thanks gimpyrobb.Al

 

[cattlerepairman]

I tried turning the engine over with the starter - no dice.

I thought the Prestolite was maybe defective, so I swapped it for the Lees-Grenville from the other engine. Still no dice. Does not click, does not turn over. This tells me that I am likely the problem. Here are pictures of my setup:

+ goes to solenoid terminal, - to engine block.


Slipped with screwdriver - the resulting flash and smoke cloud were impressive (see dent in screwdriver). Power test for batteries - check!
Batteries are fully charged and show 25 V
25 V between + terminal on solenoi and ground - that's good.
12V between + terminal on solenoid and the other terminal on the solenoid (this is the one I bridge to with the screw driver). Why?? I dont understand that part. I do understand that at 12V, the starter motor won't spin and the solenoid won't pull the starter gear forward. But should there not be 25V between these two terminals??

12 V between + terminal on solenoid and the terminal on the motor. Why? I don't know.

 

[quarkz]

OK here is a pic to help.



Again, if you have to remove the bolts holding on the starter, and lay the starter and solenoid on the ground, you can verify that the Bendix is popping forward, and the starter is spinning.

If you use a set of jumper cables hooked to the batteries, and put +24 to the post on the side of the starter, copper buss bar, Labeled A in this pic and a the negative jumper cable to the starter case or B in this pic the starter should whirl, without the starter solenoid jumping. This means the starter is good.

Touch +24 jumper cable to lug 1 and the solenoid should jump. With the negative jumper attached to lug B or the starter case.

Also whacking on the starter solenoid with a 2x4 is sometimes necessary (really!!!) to free up gunk keeping the bendix from going forward, also may knock crud off of the contacts inside the back of the starter solenoid allowing the circuit to close.

 

[gimpyrobb]

Without a clear-er pic of the terminals on the starter solenoid, I'd say it looks like you have a ground going to the 24v trigger for some reason.

 

[cattlerepairman]

Riddle solved - perhaps it helps somone else:

- the solenoid will NOT engage and the starter motor will NOT run, unless negative is hooked up to the lug on the starter motor part.
- clamping negative to the starter housing or to the engine block is NOT sufficient - the starter needs negative hooked up to lug "B" (green) in quarkz's image above

Then bridging to the small lug #1 with a screwdriver gets things going!

 

[cattlerepairman]

Here is VIDEO #1: cranking and oil pressure gauge: https://youtu.be/ilrVbn1CHi0


Here is VIDEO #2: cranking until she fires up and brief run: https://youtu.be/sCXQx-ljiD4


Oil pressure at cranking hit 60 psi, I used a manual transfer pump plumbed between the jerry can and the fuel filter to give her some fuel pressure. She fired and ran...no clatter, no knocking...just a beautiful "angry LDT" sound of the more muscular LDS!

 

[cattlerepairman]

It is now some 6 hours later and I still cannot wipe the stupid grin off my face! So happy the rebuild resulted in an engine that starts and runs! Not even the comment "yes, but let's see for how LONG she runs!" manages to depress me!