Diagnosing starter problems
 

My 1987 4runner 22re did not crank yesterday, but did so after I tapped the starter with a hammer. The same thing happened today --- didn't crank until I tapped the starter.

I'm wondering how I can diagnose whether
1) this is due to the starter (contacts or whatever) going bad, or...
2) too much resistance in the wiring.
(can it be anything else?)

My idea is to pull the cable going to the starter solenoid and test the voltage while turning the ignition? What should this voltage ideally be?

Also, I know a lot of people recommend rebuilding the starter yourself, but rockauto has new (non-rebuilt) ones for less than $100. Is it worth fixing up the factory one?

In my experience, the only thing I've seen go bad on original Toyota starters are the contacts/plunger contact in the solenoid. This has been with my family's fleet of Toyota's back in the 90s and doesn't account for starters that have been off-roaded under water, etc, only normal driving conditions.

I recently rebuilt mine, though I can't say if it was original or not to this truck. It's super easy to do but requires the same labor as replacing the starter. The contacts had worn and the starter would "run on" after it had sat for weeks. There is the very commonly experienced problem of click-no-crank which can be a combination of insufficient grounding from the BATT to the block and poor factory design of the starter circuit having several voltage drops before the solenoid is energized. Both are pretty easy to rectify. One requires soldering.

see this thread for more
https://www.yotatech.com/forums/f116...od-wow-307476/

Voltage drop across a high resistance connection is tied to the amount of current drawn. What this means is if the solenoid activation wire is not connected to the solenoid you will not see any significant voltage drop. To do this test properly you need to back probe the wire while it is connected and take your voltage reading and compare it with the battery voltage. So meter directly to battery , key to start and note the voltage. Now probe in the back of the starter connector, key on, note the voltage. Now you can compare the two.

The "bang on it" technic works by releasing a sticky solenoid. Usually caused by burnt grease, debris or other build up. It has little to do with the contacts. This said if you're going thru the effort of removing it even to have it tested on a bench tester at the local big box store. You might as well clean it and replace the contacts they are very inexpensive.

Thanks for the advice.

I pulled the starter and found that it was already an aftermarket remanufactured one. Swapped it for an Autozone one that seems to be working fine so far -- we'll see how it goes.

Was a surprisingly easy job.

Artemyk,
Please always indicate model-year-engine-transmission with your posts.
I doubt the starter was bad.
Correct, The starting system was wired wrong AT THE FACTORY.
Problem and fix explained here: https://www.yotatech.com/forums/f116.../#post52422426

This fixes an occasional problem, from his post it sounded like his starter was not working all the time. Tapping on the starter will usually get you started to get home or to where you can get parts. Everytime I have had a starter like the author described (in multiple brands of vehicles, not just Toyotas) I have either rebuilt or replaced the starter, and it always cured the problem. Your fix is a good idea for him to do with the new starter, but since his was not working at all I suspect his starter WAS bad. Getting more juice to a bad starter won't cure the problem, but if he does your fix now he shouldn't have any issues for a couple hundred thousand miles

RAD4Runner, I believe in my case the issue was the starter, not the wiring. Remember that what was in there was not the original starter, but an aftermarket remanufactured one.

I think Rad4runner's point is that the '87 models run the current for the starter solenoid through the ignition switch. Later models added a starter solenoid, so the only current through the ignition switch is the much smaller current to close the relay (the relay is, usually, under the hood so there is a shorter run to the solenoid as well.)

Your "old" starter may have been getting a little tired, so the reduced current allowed by the ignition switch was just-not-quite enough to slam the solenoid closed. Your "new" starter isn't quite as tired, so even the limited current through the ignition switch is (barely) enough. For now ...

Is Rad4runner correct? I don't know, but he makes a persuasive case about the "design flaw." After all, Toyota changed the design on later models. So there is a risk that as your new starter gets just a tiny bit more tired, your "mis-designed" starter system will allow it to fail, too.

Should you fix it? Well, your truck is already 32 years old. Do you love it nonetheless? Then fix it.

even if your starter was bad, your wiring IS flawed. correcting it at your convenience is easy, instead of doing it when it may be very inconvenient.

Good point. I will make a note to rewire the relay.

Yes and no.. More available current can overcome a sticking solenoid..

Was it a sticking solenoid, or was it a worn/dirty contact.. We will never know since the poster decides to just swap out the starter. Hell it might even of been a loose wire between the starter and battery.

I did open the solenoid, and the contacts looked fine (not worn).

If it was a loose wire between the starter and battery, why would banging on the starter with a hammer fix it?

A loose wire isn't necessarily an "open" (infinite resistance). It could be touching in only one point, so that the end-end wire is now one ohm. One ohm isn't much, is it? Well, if the solenoid takes a measly 4 amps, then there's a 4 volt drop, and the solenoid is only getting 8 volts.

Is 8 volts enough? Maybe. Sometimes. But sometimes the solenoid doesn't quite land correctly, given that it's only getting 8 volts to pull it closed. So if you bang on it, it might jiggle around enough so that 8 volts can do the trick. This. One. Last. Time.

But while your logic is sound, in the end it doesn't matter. Lots of people drive around in your vintage truck, and the starter is still working. But Toyota (and Rad4runner) wasn't happy with the design, so in later years they put in a starter solenoid. An improvement? Probably. Is it an improvement you want? Given your experience with one starter truck-up, I would think "yes."

For the same reason banging on a starter with a broke wire in the windings works. The percussion caused a wire to get a good enough contact to spin the motor. A similar thing happens with worn contacts. Even dirty contacts (arc scorching). Part A moves and contacts part B.

This of course ignores things like indecently bumping the cable with your arm while swinging the hammer.

For example I've pushed the wire loop of the starter primary cable to move the slack out of the way of my elbow which completes the circuit all by itself, then smacking the starter makes it work. So which made it start the cable position or the smack that freed up a sticking solenoid.

Sometimes you'll notice the cable end moves, that is a loose connection at the starter, but sometimes it's loose wires inside the insulation (like the corroded wires that happen inside the injector harness).

This is why the diagnostics techs make the big money and why we try to be so adament about testing things as apposed to just changing parts. Testing will show things like "hey I measured X current/volts on the battery side of this connection versus X-1 current/volts on this side of this connection (you'll notice I am quite fond of saying things like test the voltage from your battery posts, now test the voltage with your positive prob on the bayuer cable.)

As I clearly explained, a healthy battery and wiring, a smoothly operating solenoid plunger, etc can mask the problem because they would require less current.
Artemyk,
You still haven't even told us whether you have manual (incorrectly-wired starter relay) or auto tranny (no starter relay).

These guys are giving you some great advice, take notes!
Rad4runner's rewire suggestion is excellent if it applies to your vehicle and can fix a lot of no-start issues.
Scope103 is right on the money with electrical theory. Voltage is only part of the equation, if the circuit is not completed (the starter is at rest) you can read battery voltage at the starter even though the battery cable is in poor condition because there is no current flow. when the circuit is completed there would be a large voltage drop across the bad cable and not enough left over to do much work.
Banging on a starter to get it going COULD be making electrical contacts rattle enough to make a connection, or it COULD be freeing up the rotating mass in the starter just enough for a lower voltage to turn it and once it is turning it takes less amperage to keep it spinning.
The bottom line is that if you don't do the RIGHT tests it is all guessing and if you don't tell anyone if your truck has a "clutch start switch" or a "neutral start switch" it makes it hard for us to help you.
But, your problem SEEMS to be narrowed down to the starter or something very close to it.
98% of the time, in my experience, your symptom (bang on it and it starts) is either the starter or the connection for the positive cable to it.
If you apply 12 volts to the small terminal on the solenoid directly from the battery positive terminal and it starts when it did not start with the key, perform rad4runner's repair or find the bad connection in the circuit and fix it.
If that gets you the same result (click no start) hook a jumper cable (or a new battery cable) from your battery positive to the big terminal at the starter and try starting it (careful...you can short things out easy this way) if it starts it's the battery cable.
If that doesn't work try hooking the jumper cable from you battery negative directly to the starter housing or a mounting bolt. if that works you need to fix your grounding issue.
If none of that works your issue is in the starter or solenoid, either replace the whole thing or rebuild it (new brushes and solenoid contacts).
I don't rebuild starters anymore, for the price I feel it is worth my time to just replace the starter and I have never found myself having to do it again, so 5 or more years later I feel like I got my money's worth. often I have sold the vehicle by then.