View Full Version : FJ40 Checking the Ignition switch

10-21-2009, 09:27 AM
The negative cable to the battery failed yesterday. The round connection that slides over the battery post cracked all the way through. I replaced the cable with a new one, a big strong 1 gauge.

I suspect that my ignition switch has been on its way out but I missed the signs. On the 10th we put installed a new heater core and for that work we disconnected the negative cable. Shortly after hooking everything back up we had a "slow start", you know the kind that sounds like the battery is low. So, I tightened the negative cable connection to the battery post. Yesterday morning we had another "slow start" so I tightned the negative cable connection to the battery post again. Yesterday afternoon, the negative cable connection to the battery cracked.

Upon replacing the cable, the truck would not start. When the key is turned to the start position there is nothing. I checked the fuses and the top 20 amp was broken and I replaced it. All the others fuses check out fine for continuity. With the key in the On position the truck has power to the brake indicator light, the interior dome light and head lights. I did not check any of the other accessories. We put the towbar on and brought the truck home.

At home I pulled the new cable connection at the frame and cleaned the area with sandpaper so that there is a clean connection. Upon hooking it back up, I was successful in getting the truck to start once. Upon the next attempt I am back to nothing when the key is turned to the Start position. While running, everything worked just fine. With the key in the On position, there is power to all the things that should have power. The battery is at 12.7 volts.

So on to my technical questions. How do you test the Start position of the ignition switch? Can I connect a test light lead to the post on the back, ground the test light and turn the switch to Start? If I understand the circuit correctly, if the light turns on then my switch is good and I need to then check for power at the starter.

If my ignition switch tests to be faulty at Start - what is an appropriate way to set up a hot wire so that HutHut can drive the truck while a new switch is on its way?

10-21-2009, 03:48 PM
Give me a call I can sort it all out in about 10 min or less. Even rig up a maneual starting wire for the time being.

10-22-2009, 08:21 PM
Being more of a web mechanic and indoor dog I didn't mess with this last night. This afternoon I still had nothing when turning the ignition to start. I ran a hot wire from the starter to the battery (thanks Tim) and it turned right over and started:D. HutHut was giving me a hand and very surprised/impressed at how easy it was to use the "key wire" to get the truck started.

I removed the ignition switch and tested the wire to the starter for continuity. The wire checks out fine. Since the problem Tuesday night each time I tried to start, I would hear a click when turning the key to the On position and no click when turning the key to the Start position. While I had the switch out, I put the key in and cycled it through the various stops. There is a very clear click in each one. I put the ignition switch back in and it is working fine for now. HutHut has the "key wire" in the glove box if it is needed. A new ignition switch is on order from Toyota and should arrive on Monday.

For you owners of older 40s, what tool do you guys use to remove the ignition switch ring that holds the switch to the dash? I used some snap ring pliers and fortunately the ring was not on very tight.

10-24-2009, 11:54 AM
I checked the fuses and the top 20 amp was broken and I replaced it.

That fuse is for the lights (headlights, tail lights, etc.). They should work no matter what the ignition switch is doing.

So on to my technical questions. How do you test the Start position of the ignition switch?

The quickest method is to disconnect the wire that goes to the starter solenoid, connect a voltmeter to it and the other lead to ground, and check for battery voltage when the switch is turned to the crank position. If you have voltage, then the switch, wiring and fuse are all good and the solenoid is bad (assuming good ground from starter to frame). You can also do what you did below and simply bypass direct from battery + to the solenoid and see if the motor cranks.

If no voltage, then check the fuse (it will be one of the 3 bottom ones, which pass through the ignition switch to power their loads).

If the fuse is good then it is either the switch or the wiring/connections. I've never had the switch out of mine, but if you can access the connections and see if voltage is going in, but not coming out of the terminal that goes to the solenoid then the switch is bad. Is seems from your follow up post that is your case.

If my ignition switch tests to be faulty at Start - what is an appropriate way to set up a hot wire so that HutHut can drive the truck while a new switch is on its way?

It sounds like you've got it figured out. Just jump direct from battery + to the solenoid.

10-28-2013, 02:10 PM
Hey guys, I'm bumping Ricardo's old thread.

I'm having an intermittent starting issue with the 40. Saturday I went to turn it in and nothing, not even accessories coming to life. Sunday, it fired right up without issue, and this morning nothing again.

I've tried several highly technical things like, jiggling the wires at the connection of the harness and the ignition switch pigtail, wrapping the ignition coil lightly with a screwdriver handle and a few other things that have "worked" in the past.

I'd did replace the starter and the ignition switch assembly last year as well... both have been working fine for a year now.

I'm heading into the garage now with a multimeter and my manual to see what's happening. Besides fuses and seeing if I am getting power to the starter solenoid what else should I be poking at?

Thanks in advance

10-28-2013, 02:59 PM
Sketchy fusible link?

10-28-2013, 03:56 PM
A couple of less highly technical but also important things would be...

Check the battery cables, white crud can cause the symptoms you describe.
Clean the ground connections.

Your observation of no electricity to the accessories would have me concentrating on these items first. :thumb:

10-28-2013, 05:29 PM
Ethenol in our fuel!!!! :) whoops wrong thread....

I switch batteries around constantly and am amused how many times you have to "attach" the battery terminals. How a 360 degree lead clamp on a lead post isn't making contact is just nutty but.... it happens. If you listen closely, you can hear the current arc just before it kills the connection. Jump out, wiggle the cable and you are off!

The only real fix is to buy good quality terminals and keep them clean. I don't know the science behind it but, I am guessing lead (or whatever they make them out of these days) oxidizes and only a small portion is transferring the current. This isn't the corrosive white crud either (lead sulfate?) just clean old cables and a battery that probably should have been retired twenty years ago.

10-30-2013, 05:03 PM
I've had some issues in my 71 FJ40 in recent days, but the root cause is that my 12 year old red top is nearing the end of its life. It is getting soft (voltage droop when cranking) after it has sat for a couple days and it is cold out. It measures only around 12 volts with no load after it has sat for a while, and droops to less than 8 volts while cranking, not enough to get a decent spark at the plugs. It will take a charge just fine and last for a day or two, but I am guessing the AGM is starting to get some internal leakage current.

My early morning cold start fix is to jumper directly from the battery positive terminal to the load side of my ballast resister. Ultimate fix will be to get a new battery. Most of the time I've just been driving one of my other cruisers...:rolleyes:

10-30-2013, 05:31 PM
Thanks guys, I got under the dash yesterday and chased wires with the voltmeter, I didn't go the whole way in figuring out where my bad connection was happening. However, with a little tension put on the connection from the dash cluster to the 4 pin connector to the steering column it would fire right up. I could also hear a faint click like a relay firing when I put tension on the cables as well.

My fix due to time was to zip tie the harness to keep that slight tension on it and its worked flawlessly since. :hill: I'll track it down soon and get the right fix. I did notice this first started showing up after repainting my dash cluster cover about a year ago.

Thanks for the help.