Electrical question about starter/ground

The larger negative cable bolts to the engine or transmission and handles the 150 plus amps for the starter motor and the lower current for the generator. The engine is mounted on rubber engine mounts to isolate vibration, but the lights and all the other electrical circuits need a ground path for their current to get back to the battery. That is the purpose of the smaller negative battery wire that bolts to the body.

There can be other unintended ground paths for current to get back when that small wire is cut. The most common is the steel throttle cable, but that is a very poor connection. There are also usually multiple ground straps from various places on the engine, to the body, to prevent radio noise interference. Those could be providing the ground for the rest of the circuits, through the engine. While those other ground straps might be doing the job for now, they aren't meant to be reliable electrical grounds for those other circuits, especially safety circuits like air bags and anti-lock brakes. Either fix the cut wire or run a new one and bolt it to the body at a paint-free point.

The intermittent starter operation you described is extremely common with the little silver Nippendenso starters. The copper contacts in the solenoid burn away and cause the intermittent single loud clunk with no-crank. Most people just replace the entire starter, but the contacts are available at auto parts stores and farm and home stores. The kits come with four contacts. The "battery" contact is the same in every starter, from every year, regardless if it's on a Toyota or Chrysler product. You also use the one "starter" contact of the remaining three that matches what you took out. The last two terminals are not used. There is no way to tell which version of "starter" terminal you have until you take the solenoid apart and look at it. While the internal parts changed slightly over the years, the complete starters all interchange between those years, so you do not know what year a previous replacement starter came from. That is why they always give you all three "starter" terminals to pick from.

If you can find the kits in a hardware store, it is going to be for a Chrysler product, and there are two to pick from. You can use either kit because the contacts are the same in both. They come with a new plunger too. That has the copper contact disc, but that usually does not have to be replaced. There are two versions of that plunger, hence, the two kits. The stem is 1/8" longer on one of them, but it is irrelevant because Toyota uses a third, totally different version, and you can only buy that through the dealer's parts department. As long as you do not need to replace your plunger, you only need two of the four contacts, and both Chrysler kits will fill the bill.

You can also buy just the two contacts from a starter / generator re-builder, if you have one in your area. All larger cities have at least one. You will pay less by buying just the two contacts you need, but you have to take the old ones in to match them up to the new "starter" contact. When you compare the new contacts to the old ones, it will be real easy to see where the old ones have burned away.