PO modified starter circuit questions

[DeadParrot]

It was this way when purchased. One PO was a FD who passed along the maintenance records. One WO shows replacement of the under dash starter relay. Whoever did that did a good wiring job. Relay later failed shut which I verified by opening up. Another WO shows replacement of starter with a gear reduction starter.



TM and other wiring diagrams say the ignition switch wire is yellow. The Orange wire that was fed to the engine side purple wire does go hot when ignition key turned. There is also a cut yellow wire in the pic. Doesn't react to key turn.

Was going to do the doghead upgrade when I found the switched wire to the starter relay doesn't react to key turn.

Has anyone seen this bypass done and is there a recommended way to reverse to factory?

Is there a way to tell what voltage starter was installed? Can't see any part numbers and the WO doesn't specify. Unless there is a hidden heavy wire going to the starter, it is being fed 24V. Whoever put the starter in also didn't complete the support bracket installation despite a specific WO line to that effect.

The Orange wire that fed the purple wire is 12V. Will 12V activate a 24V solenoid? If the starter is 12V, how long will it last if fed 24V as it is now?
Worried that feeding 24V to a 12V solenoid might let the magic smoke out.

It does start fine with the orange to purple wiring setup.

 

[cucvmule]

Try going to the post Viet Nam to Desert Storm forum to CUCV Sticky Helpful Threads, then CUCV color wiring diagrams. That will get you started to figure out what has been done and how to repair back to original or help you to modify.

Plenty of TM's also for the whole truck, with the part numbers also. And also trouble shooting sections also.

 

[nyoffroad]

"orried that feeding 24V to a 12V solenoid might let the magic smoke out." that's for sure!
12v to a 24 starter will activate the solenoid but will not turn it over and will cause the starter to stick and 'lock up' the engine. I know this from a guy that gave me a "blown up 6.2 and it runs like a top once I hooked 2 batteries to it.

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[Terracoma]

The Orange wire that fed the purple wire is 12V... It does start fine with the orange to purple wiring setup.

Unless there is a hidden heavy wire going to the starter, it is being fed 24V.

If the starter is 12V, how long will it last if fed 24V as it is now?

Based on your description and your photos, you are triggering your solenoid with 12v, as it is now.

EDIT: Looks like we posted at the same time, and you got it figured out... I don't think you're necessarily hurting the solenoid by under-volting it on the trigger side, but you're probably not doing it any favors either.

View attachment 779739

The purple wire seen in the above photo is Circuit-6, as found in the F-1 Starting Circuit wiring diagram... Circuit-6 begins at the starter relay, passes thru the bulkhead connector to the engine compartment, jumps into that big wiring bundle, snakes around the backside of the engine, and drops down to the starter solenoid.

Circuit-6 is the starter solenoid's trigger wire, as signaled from the ignition switch, via the starter relay under the dash... I've highlighted on the diagram below what I think has been modified on your truck, colored appropriately to match.

Has anyone seen this bypass done and is there a recommended way to reverse to factory?

In short, you need to reconnect the yellow ignition switch wire back to the starter relay... There's a splice somewhere between the ignition switch (on the column) and the starter relay (under the dash), where the yellow wire becomes a purple wire with a white stripe. This purple/white wire is the trigger wire for the starter relay. However, the PO/FD substituted that orange wire, and you'll need to determine where the transition occurs and how best to redirect it.

In addition, you'll also have to reconnect Circuit-6 at the bulkhead connector on the engine-side, which may be a hassle if the PO/FD cut the wire too close to the connector... After that? Install a quality starter relay, and connect it per the TM.

 

[DeadParrot]

I cut back some of the tape job(it looked nice, just like factory), and found the splice where they cut the yellow wire from the ignition switch and spliced in the orange wire. Solved my confusion. The diagrams show a yellow wire and the one that was fed to the purple wire was the same color orange and size as another one in the bundle. They were feeding the 12v direct off the ignition switch to the starter solenoid which is enough to trigger it.

Trying to figure out if the installed starter is 12V or 24V? One would hope the shop would install the correct one but it doesn't take much searching to discover several cases where that would be false.

Will a 24V starter spin much if fed 12V? Easy enough to perform that experiment. Will it do it much harm or just spin real slow? It is a gear reduction starter.

Terracoma - was typing when you were. There looks to be just enough purple wire on the firewall side to reconnect. I think a shop did the work for the FD. Already have the relay specified in the doghead upgrade thread.

 

[Terracoma]

Short of dropping the starter down to inspect and check for stickers or identifying marks, I'm not too sure...

Doubtful that a 12v starter would last very long on a 24v diet, so I'm betting that it's a 24v model.

Terracoma - was typing when you were. There looks to be just enough purple wire on the firewall side to reconnect.

If you can't quite reconnect them, and you're feeling brave... You can try disconnecting the two halves of the bulkhead connector (via the bolt in the center), and push out the offending spade pin with a small screwdriver.

There's a little tab on each spade that holds them inside the connector. Just depress the tab on the spade side, pull outward on the wire side, and the spade (with the purple wire stub still attached) should slide right out... Repair the wire, and simply push the spade back into the connector until the tab clicks back into place.

 

[joshuak]

If you need to replace the spades in the bulk head connector, I found Packard 56 connectors to be a direct replacement. Bought them at Napa.

 

[doghead]

It's possible to have a 12v solenoid and a 24v starter motor(or visa versa).

Inspect what you have.

 

[DeadParrot]

Finally got back to this after waiting for parts and taking time for muzzle loading deer season. (Oct 26-Nov 3 here).


After dropping the starter, found a Delco-Remy sticker and a 12V sticker. Also discovered a broken support bracket hanging off the starter and a second complete bracket hanging off the motor. Glad I decided to drop and inspect the starter. Assuming the 12V sticker is correct, seems a 12V starter will last a decent time when being fed 24V. Finding this prompted the new parts orders.


Installed the new 24V starter(probably a China version by the look), new GM support bracket and two new GM starter bolts. (received the simple hex head version so added a washer.) Got the under dash wiring puzzled out and restored closer to original.


Everything seems to work fine now including the new Doghead spec starter relay. Don't notice any difference in starting speed.


It passed the bent paperclip gear spacing test. Spray painted the starter gear as a way to double check gear fit after a start. Looks to have good engagement and it isn't bottoming out.