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Looking more closely at the H-30 diagram above, I don't see a difference in the wiring between the Prestolite and a GM/Delco type starter. Both have 3 terminals: the big wire connected to the battery (not switched), a starter switch connection that energizes the internal solenoid, and an ignition connection that is connected to the battery when the starter solenoid is engaged.

The Ford solenoid and starter (like used by AMC) does essentially the same thing, but splits the function between the starter proper and the fender-mounted solenoid.

Looks like the geared starter replacement has two connections: the big wire (not switched) and a connection to the starter switch. If there is no third terminal for the ignition, one could connect the starter wire to the ignition. Lacking the switch, you must add a diode between the coil and starter switch. Neglecting the diode drop, that would perform the same as the switched ignition connection.

I'd mention - adding the Ford solenoid is 100% redundant here, unless the geared starter has no ignition terminal. Even then, I'd skip the extra solenoid and add the diode. The solenoid is just something else to fail, and these parts are a common service item. The contacts that bridge the battery to the starter get badly pitted due to arcing.

BTW, if you have the opportunity, it's instructive to look inside one of these Ford-type solenoids that has failed. There is a copper disk that bridges the two big terminals when the solenoid is energized. If you were cheap or desperate, you could flip the disk over and use the backside to bridge the contacts for a while - assuming the coil still works. BTDT.

On my High Torque starter I used a jumper from the solenoid to the large stud. Jeep/Ford starter relay powers the stud and the solenoid is energized at the same time. Ive been running it this way for 2 years now without issue.

Sorry it's been a while since I've given an update--baby number two joined our family in November, and then it was holidays and family for two months!

I have made some progress however, I ended up pulling most of the factory wiring. I installed my shiny new alternator and a 4ga charging circuit, got the new (to me, came with the project truck) starter installed, installed the relay, turned the truck over a few times, and burned up the relay. (no 12v from the post going to the starter when the relay gets its 12v ignition signal). I also discovered that the ballast resistor was bad. It was replaced, I set up a temporary work-around for the bad relay and am successfully using the ignition connection on the high torque starter to kick the bendix out and turn over the engine.

I didn't have spark, and I think that it's the distributor giving me grief now. Any thoughts on replacing my points and condenser with a pertronix ignitor II?

I'll have to take a couple pictures when I'm back at the shop.

So since January I quit my job as a test engineer for a fitness company and started a new job as a warehouse/facilities manager for an agricultural company. The change-up has made for continued slow progress, but things are still moving along.

I did a compression test on the AMC 327 once I got it cranking, and it looks like the four middle cylinders have relatively low compression. Doing my best to read the pressure gauge, my results are as follows:

Cyl 1-86 psi Cyl 2 - 70 psi
Cyl 3-75 psi Cyl 4 - 35? psi
Cyl 5- 50 psi Cyl 6 - 23ish psi
Cyl 7- 100 psi Cyl 8 - 60 psi

I haven't done a wet test to see if it's the bottom end or if it's the top end. I've priced out BJ's Full Sized Jeep Parts gasket kit at $252, piston rings look to be around $50. Getting into the weeds with rods and pistons and everything else that goes into building an old kind of rare engine, I'm starting to look at doing an engine swap. I am leaning toward an LS, it's been done before and they are relatively cheap and plentiful and there's a ton of support for the platform. I am currently saving my pennies to pick up a donor vehicle.

Anyway, a lesson learned -- check compression before you start buying parts for an old engine of unknown quality.

In the mean time, I pulled off the bed. The rust was worse than I thought, and has further reaffirmed my idea to build a flat bed. The fuel tank had a hole and was full of varnish, and the filler neck self-disintegrated. I am worried that all I will have left when I'm done with my truck is the frame and cab. I'm looking pretty seriously at an axle swap as well, I think I can track down a superduty dana 60 for the front and sterling 10.5 for the rear for under $900.

As a tangent, I had to replace the water pump on my 2012 Liberty so that ate into the ol' vehicle budget this last month.

Hmm. Your compression numbers suggest worn rings. If you had a bad exhaust valve, you'd have one low cylinder and the rest more uniform and higher. It is possible to patch up an engine like this with new rings. They can only be cast iron - no moly or chrome - and they won't last as long as when you bore the cylinders to straighten them. Depends on how much life you want from the engine.

An olde-time overhaul would be grind the valves, replace the rings, replace the rod bearings. I'd likely skip the bottom end and fix the valves and rings. Main sources for 327 engine parts are Kanter Auto Products or Egge Machine, IIRC. We love how BJ's supports these Jeeps, but they are aggregating parts from other sources. There are AMC specialists too; maybe check the the AMC Forum for other sources. Looking at RockAuto, they have rings for that engine with lots of options. If you don't find engine parts for this Jeep, look under 1965 AMC Ambassador with a 327.

Fixing the 327 won't be cheap, but I'd predict you won't save any money by swapping to a different engine. Depends on what you want.

Show us some pics of the bed rust. Bed floors can be fixed with materials from other beds or just plain steel.

Sorry for hijacking your post.

There is a lot of info regarding the Prestolite starter on this thread, so I thought it would be appropriate. Can delete if needed.

Regarding the starter motor switch cover, if the ignition resistor terminal is missing - can I substitute a bolt or something? I saw mention of flipping the copper contact disk... How does it come off? Seems like it's integrated with the switch cover.

Pictured is how the factory one looks. The one I am rebuilding is a spare. The solenoid terminal is connected to the coil windings which is why it isn't pictured.

Sent from my Pixel 5 using Tapatalk

I have repaired the Ford-type solenoids (like the Standard SS581) by flipping the contacting disk.
https://www.rockauto.com/en/parts/stand ... enoid,4188
These solenoids contain two large contacts for the battery and starter motor, and the disk bridges those contacts when the solenoid is energized. You need to drill the rivets to get to the disk, do your thing, then replace the rivets somehow. Interesting, but most would buy a new solenoid.

Not sure that applies to the Prestolite.

JMO - I would skip the "resistor" bolt replacement and add a relay for the resistor bypass at starting.

tgreese wrote: ↑Thu Mar 14, 2024 6:58 am
Not sure that applies to the Prestolite.

JMO - I would skip the "resistor" bolt replacement and add a relay for the resistor bypass at starting.

A relay being something like this? https://www.amazon.com/Cole-Hersee-2405 ... B0064MX7US

Are the terms solenoid and relay used interchangeably? This just describes a device that uses electromagnetic coil windings, right?

The Prestolite has an internal "solenoid" that appears to actuate the bendix assembly, so I just wanted to make sure I understand the terms correctly.

Should I just follow the wiring diagram CasualYT1300? I also plan to convert to a single wire alternator so I can run more accessories, so this will be a good reference.

Thanks for all of the info y'all have shared. I am a novice when it comes to electrical systems. In fact, I have studied this thread and the TSM more rigorously than I did for any school exam lol. To the extent I put together a doc to better track and study this project.

(Lots of pics for anyone's reference)
https://docs.google.com/document/d/1l6P ... t1zSk/edit

The term relay is pretty well defined as an electrical switching device that's controlled by a solenoid. Strictly speaking, a solenoid is a winding of electrical wire in a cylinder, and is a type of coil. It generates a strong magnetic field aligned with its long axis. https://en.wikipedia.org/wiki/Solenoid

Relays and contactors are pretty much the same thing, with relays being smaller and contactors being larger. Both contain a solenoid that switches the contacts, because the solenoid makes a strong local magnetic field that can close the contacts quickly and securely.

Solenoids are strong and can do different types of work. The SS581 contactor I linked above would be better called a contactor, rather than solenoid. It has a solenoid coil in it, but solenoids can be used for other purposes, like the valves in your washing machine that are solenoids (solenoid valves).

I think the use of "solenoid" for the starter contactor in an automobile is historical and somewhat anachronistic. Maybe relays were widely called solenoids when Kettering invented the electric starter ... dunno. Relay, contactor, "solenoid" ... in my mind, all different names for the same device. Up to the reader to interpret based on context.

Now, there's a lot of ambiguity here that must be resolved by the reader. You say that Prestolite starter has a solenoid in the starter body that bridges contacts and runs the starter motor (like the Ford type SS581) and throws the starter gear into the flywheel. That's a solenoid in the sense of being a contactor, but it's also a solenoid that does mechanical work to move the starter gear. The Ford starters have a similar scheme, but use the field coils (not solenoid coils, instead field coils) to pull a big steel slug on a hinge into the field, and throw the starter gear.

In the Ford starter, the field current both throws the gear and powers the motor after switching on the armature. Looking at your link, the Prestolite has to have both the solenoid and the motor field. I assume that there are contacts in the Prestolite that switch both the field and the armature on, once the gear engages with the flywheel.

Per your question, the solenoid must remain on while cranking. It works against the spring which would withdraw the gear if the coil were not energized. Solenoid off would also shut off the starter motor, I presume. The R terminal connects to the battery terminal when cranking, not the solenoid. When the solenoid is off (not cranking) the R terminal is disconnected from the battery. The solenoid does not connect to the R terminal, and the R terminal is open when not cranking. Thus it does not matter that the ignition energizes the R terminal when running, since it's open then and not connected to anything.

Not sure about the Prestolite starter, but I expect the "R" terminal is used to bypass the ballast resistor when starting. This gives more juice for starting, and improves ignition performance while cranking. You could do the same thing with a $5 relay controlled by the starter switch. https://www.parts-express.com/12-VDC-Wa ... quantity=1

This rambles a little since I'm writing it quickly and off the cuff. Welcome to follow up if somethings not clear.

All right.
I think I've about got this thing figured out.

There are 2 primary contact points. One to power the solenoid "shuttle" that engages the bendix into the fly wheel, and one that provides power to the brushes and field coils.

The field coils and brushes are positively charged, the resulting magnetic field spins the armature and commutator within the pinion housing.

In the factory configuration the starter motor switch cover receives constant 12V power, but it is only delivered to the internal contacts when the ignition switch is turned on. This is accomplished by some kind of "finger" (as coined by the TSM) that is housed below the starter motor switch cover.

The starter I got my hands on is missing this, so on to the updated version.

With the new configuration suggested by T-Greese, the relay will take the place of the internal "finger", supplying 12V power to starter internals. This will be triggered by the signal from the ignition switch wire, which will also power the solenoid shuttle.

When the ignition switch is released, the whole system will lose power and everything will return to dormant / normal operation state.

Sound about right?

Yeah, I think it won't work. You need the built-in delay that's normally provided by the finger circuit. In the original config, the starter motor starts running after the shuttle throws the gear into the flywheel. I'd guess this maybe 100-200 milliseconds after you turn the ignition switch to start and the signal is sent to the starter to run.

You can see the problem here. If the motor is running before the gear is meshed, it will grind or not engage at all. Both the Ford and GM starters include a mechanism that provides this delay. The GM starters have two wires, one for the solenoid and one for the starter motor. These work the same as the Prestolite, except the solenoid is an external component that can be replaced (and often needs replacing).

The Ford starters are different in using a single wire. They use the magnetic field of the field windings to throw the gear, then switch on the armature after the gear meshes with the flywheel.

You understand that, to do what you describe, you'll need to add a permanent connection between the big post on the starter and whatever remains of the finger. The Ford solenoid is like a big switch - no delay. That's normally handled by the design of the Ford starter itself (like the Prestolite).

What you could do - have the finger energize the Ford solenoid after the gear has meshed. This would require sending a wire from the starter back to the solenoid, to start the motor. You'd still need some kind of physical contacts in the starter to energize the Ford solenoid.