Unusual Starting Problem

[pkinfinity]

I have an 89 4runner SR5 with a 3.0L V6. For the past 10 years I have had an intermittent problem starting the vehicle. The problem occurs when the 4Runner gets hot, usually after several stops for errands. Usually this occurs in the summer, but it can occur at other times of year. I replaced the starter twice, replaced the battery, replaced the ignition wires, and replaced the ignition. After the 4Runner cools down (sometimes for up to 20 minutes) then it starts as it should, without hesitation.

While the starter does not turn, other electrical systems operate normally - radio, power windows, lights.

One other oddity has been growing more apparent. Sometimes, when I turn the ignition key, there is a slight delay before the system engages and the starter turns. But the starter does turn and the 4Runner runs great.

Any suggestions?

 

[Theslammer21]

ignition switch or cylinder is always a possibilty

 

[pkinfinity]

Looks like it was the wiring harness

So I had a relay installed for the starter. Its been working well for a week. I've driven it several times, on hot days with several stops during the day.

 

[pkinfinity]

So I had a relay installed for the starter. Its been working well for a week. I've driven it several times, on hot days with several stops during the day.

Almost two months now - and it has been driven in the Texas heat. So it looks like the relay worked.

:cowboy:

 

[RAD4Runner]

Not Unusual Starting (cranking) Problem

So I had a relay installed for the starter. Its been working well for a week. I've driven it several times, on hot days with several stops during the day.

Almost two months now - and it has been driven in the Texas heat. So it looks like the relay worked.

How did you install the relay? Got Wiring Diagram?

pkinfinity
Glad your's worked now.

This is not an unusual problem with first gens. Many factors could cause this but one thing in common with many IF, and only IF, wired similar to 1986-1988 Runners is wiring flaw explained here. This is fairly easy to diagnose and cheap to fix without adding or replacing parts (one needs to verify his schematic for his particular truck).

Summary of flaw:
Power supply to contacts of starter relay comes from ST1 contacts of ignition switch. 12-Amps of current for energizing starer solenoid passes through starter relay (meant to pass high current) and ignition switch contacts (not meant to pass high currents). This unnecessarily fatigues ignition switch contacts, which creates high resistance, that causes too much voltage drop When high current tries to pass.

IF this is the case, fixing Toyota's wiring, even if other things are causing no-crank issue, will help extend life of ignition switch.

Fix is here.

 

[pkinfinity]

RAD,

I had the relay installed by a Toyota expert in Austin. Bearden Automotive. The small shop only works on Toyotas and Lexus.

But the way I understand it, the charge travels from the battery via the wiring harness to the solenoid, which pushes a plunger that activates the starter, ultimately turning over the engine. But on older Toyotas (4Runners and Camrys especially) the wiring harness holds more resistance as it ages. And the resistance increases with heat. So the signal from the ignition is fairly weak and weakens as it passes through the wiring harness to the solenoid / starter. This ultimately prevented the plunger from my solenoid from fully engaging the starter when the system was hot.

Apologies if my armchair electrician's explanation is not exactly perfect or 100% accurate. I only do minor maintenance on my vehicles now. I've become more of a "point and pay" kind of guy.

 

[pkinfinity]

RAD,

I went to your link after I submitted my response. Dang. You are not an armchair electrician. I have not had to read a circuit diagram since high school physics class.

Hopefully your post will help others solve their problems quickly. I wasted nearly 10 years of wandering from repair shop to repair shop trying to fix the problem.

 

[RAD4Runner]

RAD,
But the way I understand it...the charge travels from the battery via the wiring harness to the solenoid, which pushes a plunger that activates the starter, ultimately turning over the engine... the wiring harness holds more resistance as it ages... And the resistance increases with heat... So the signal from the ignition is fairly weak and weakens as it passes through the wiring harness to the solenoid / starter. This ultimately prevented the plunger from my solenoid from fully engaging the starter when the system was hot...
I only do minor maintenance on my vehicles now. I've become more of a "point and pay" kind of guy.

Pretty Runner you've got there!

All sound valid. Old thin wire + corrosion + heat = high resistance. If the 89 also has wiring flaw I described, ignition switch contact resistance also add to that resistance. So that shop probably installed one similar to the Hotshot, discussed on other posts, which is a good fix, too.

Yeah, speaking of harness, I wanna upgrade (myself) my headlight wiring so wires will be shorter and thicker, then convert to Roundeyes or something.

RAD,

I went to your link after I submitted my response. Dang. You are not an armchair electrician.

Hopefully your post will help others solve their problems quickly. I wasted nearly 10 years of wandering from repair shop to repair shop trying to fix the problem.

LOL!
Yeah, I hope so, too. If only people would read first, and not jump to conclusions and start replacing everything they suspect =D

I'm only equipped to do minor maintenance and electrical (multi-meter), but our classics are so easy to diagnose that we can troubleshoot the problem and POINT exactly at it so mech does not waste our money and time with his guesses.