This is a cut and paste of a thread I put on a Toyota truck forum
I'm getting no responses there, and I know there are a lot of good mechanics on this forum, so decided to repost it here for input:
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HELP: starter not activating, solenoid clicks

So this was an intermittent problem for me for about a month. Each time in the past I would wait a minute and try again with a successful start
then last Thursday (in the garage luckily) I turned the key and heard the click, with no good outcome
This Truck is an 86 4x4 with automatic transmission

I bought a starter, foolishly thinking the solenoid had failed and didn't bother to test anything
guess what, the new starter didn't work either
I began testing things and found that the solenoid wire was only sending 11.6V when the key was in the start position
when I jump a 12.5V battery wire directly to the solenoid it cranks as it should

So I started tracing the wire circuit to see where I was loosing voltage
I discovered that the automatic truck has a neutral safety switch on the transmission
I tested and found it also was only receiving 11.6V at the switch wire

next I pulled the ignition switch
at the switch wiring, both of the power wires are registering 12.4V
when the key is turned to the run position, that voltage drops immediately to 11.6V
and in the start position it remains at the 11.6V reading.

so I'm leaning towards a circuit in the "run" position is putting enough draw on the battery to decrease the necessary 12V's from getting to the solenoid

oddly, and this may be a clue that I'm not smart enough to figure out: when I disconnect the starter switch entirely and jump a 12V battery source to the solenoid wire as it exits the ignition switch, I still get the "click" without exciting the solenoid.


my first question:
what all is in the pathway of the solenoid wire at the switch?
I've discovered it goes through the neutral safety switch at the transmission
I've discovered it goes through a relay behind the glove box that clicks each time I apply power to that wire
is there any other system that it goes though I should be checking, and is there a way to test each of these items its passes though?

My second theory is still that something in the run circuit might be lowering the voltage before I engage the start position on the switch.
but weird that a direct 12V source to the solenoid circuit applied at the wire to the switch isn't exciting the solenoid
do I have 2 problems?

thanks for any help or tips
I'm pretty stuck and don't want to just buy more components (like I did the starter)
I don't know if there is a common failure point/component on these trucks I should be checking first?

brant

When you are taking this 11.6 reading at the starter solenoid wire, are you getting 11.6 with the wire still attached to the solenoid? Or are you taking this reading from the wire disconnected?

The reason why I ask if it is still connected is 11.6 during request is not right. believe it or not, its too high.

Depending on how long you multi meter cables are you made need 2 people for this.

Keep the request wire hooked to the starter. Clamp, or alligator clip the b+ from your DVM to the request terminal on the starter solenoid. Just clamp or clip the black to a good engine ground.

Now try to start the truck while watching the voltage on the DMV. HOLD the key in start request and see what the voltage says.

If the voltage is too low, which I suspect, the wiring is breaking down, and you just have to add a new wire.

Also do this test on the big red cable on the back of the starter, I have seen large gauge cables break down too.

Another thing you can do which use to be common fix on old vw bugs is wire in bosch 4 prong relay, kinda a bit of a band aid but it works.


Do these tests, if they don't help you I can go on identifix here at the shop and see what is the common failure for you truck.

I tested it both ways...
reduced voltage when disconnected also
brant

this is good info
I will have to test more tonight.
I was using a long jumper wire to test from the end of the wire I would normally plug into the solenoid.... through the long test jumper wire... into the cab of the truck where I was sitting with the volt meter in hand

I have 12.5V at the big starter wire (direct from batter to starter) but now realize I was testing that one in stationary status and not when keyed onto the start position of the switch. I will re-test that under load tonight

when you say DMV, is that the same as ECU?
I have not unplugged the 20some wires at the ECU yet to test those

thanks again for the education and help!
brant

DVM is digital multi-meter. If the big red cable goes to like 6 volts or less under load, you have found a problem. Most of the time when a big red tests bad its usually the connection at the battery. But every so often its the cable itself.

God luck and keep me posted.

BTW, on this truck this problem shouldn't have anything to do with the ECU, so I would just leave it alone.

DMV.... thank you
that makes so much sense, don't know why I didn't think of that one.
I will get that test tonight.
actually the very first thing I did was clean the batter cables, but that doesn't mean the cable hasn't deteriorated under load as you point out
I will get that test tonight

thanks again!

brant

Bypass the neutral safety switch and check voltage again.

Toyota has a starter relay. safety switch only interrupts the relay coil. Relay pulls power from the battery and engages the starter.

My money is on a bad relay.

Alldata doesn't show a starter relay on an automatic. MT only, works with the clutch switch.

It's the same circuit. Automatics use the neutral safety switch, manuals use the clutch switch. Both circuits go to the same relay. Most likely the relay is under to hood in the fuse main panel.

Here it is... 1986 Toyota pickup 4x4... Automatic, no starter relay.

Click to view attachment

Dude, there is a starter relay shown in the middle of your picture.

Look closer, see where it breaks in....one leg is m/t the other leg is a/t. Diagram shows both transmission options.

maybe the switch is bad. If the AT does not use the relay, the neutral switch would need to be high current (rare) and is most likely bad.

Could be, or it could be the big b+ cable or the solenoid wires. Have to do the tests to know.

This is good info too. You can probably just unplug the neutral safety switch and use a jumper right at the harness connector. If it starts you confirmed the safety switch is bad. Just make sure its in park before you try this or you could be run over.

Hopefully after trying this stuff the fix will be easy. If none of this is conclusive it could also be the ignition switch itself.

Try replacing the connector for the start wire to the solenoid at the starter. It sounds like a breakdown of the current path to the solenoid. (The solenoid works when you provide a power source from another wire, does not work with regular wire hooked up.) I experienced a similar problem and found the connector at the starter solenoid had several broken strands in the wire at the connector. Cutting the connector off and replacing cured the issue. A quick test would be to take a voltage reading at the wire where it connects to the solenoid at the starter, both with the wire connected to the solenoid and with it disconnected. Both readings with the ignition switch to start. If the disconnected is 12.4 and the connected is somewhat lower, this means that the solenoid is dropping the voltage down but there is not sufficient current thru the wire to close the solenoid.
Tom

Did you use an old solenoid?

I fixed my similar starter issue with a $7 copper washer in the solenoid. The connection wears down and you get intermittent starts.

An update....


I tested voltage at the main battery wire to starter, under load

no significant power drop when in the start position... a little with the load, but it still remains above 12V

I put a heavier charger on the batter and had it up to 13.5V during last nights testing

I replaced one of the main chassis grounds from the motor to firewall and also cleaned the main batter ground from battery to engine bay
and finally cleaned the heavy battery ground cable from battery to motor. No change.

I disconnected the neutral safety switch and did pick up a .5V increase with that out of the system. So instead of approximately 11.6V in start position (measured at the switch) I'm now over 12V at the switch in the loaded start position.

With that extra voltage of having systems eliminated from the load, I now get a solenoid activation about 25% of the time.

I was sent a thread link from some guys at the Toyota truck forum. They present that it is common knowledge (amongst Toyota truck guys) that the 1986 - 1990 4 cylinder trucks were wired from the factory to run full voltage through the ignition switch and the intermittent click of the solenoid not receiving enough voltage to activate is a common problem. Their solution is to add a relay into the start circuit that feeds direct battery power to the solenoid when activated.

Tonight I will reinstall the original starter and then verify everything is the same. I fully expect it will be. I will then purchase and install a starter relay

I'm having 914 deja vu at this point with starter relays...

do you guys know if the relay has to be of a certain rating to carry the full battery voltage. I assume the triggering power from the stock switch will be at the 11.6V and the battery itself around 12-13V
will any relay work, or do they make heavier ones for this kind of load?

I have an extra 914application ford solenoid relay but its too big and clunky for this application, so intend to buy a more modern looking square black relay for general purpose.

thanks a ton guys
I'll let you know over the weekend if the relay is the solution
apparently in Toyota truck land, I'm being told that dozens of people have made this wiring update and had success for years and years.

it was a brand new starter with solenoid.
same exact symptoms as the heavy duty starter that was on the truck when I purchased it 5-6 years ago.