Hello everyone. I just bought a 90 4runner 3.0 auto. It has quite a few problems, but before i get to those, heres what happened:
-driving home cruising at 50, truck shut off. Batt power good.
- the oil temp battery and brake indicators came on. I rolled to a stop and haven't been able to start since.
- ive checked my fuses. All good. New battery and alternator. I read here about it, everyone said alternator or an electrical short? Idk what to do. It turns over great. Power is good. But wont start. Does anyone know what this may be? Thanks.

 

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Your dash lights aren't relative to your problem, it's normal behavior for those lights to be on when the key is in the run position and the engine is not running in fact you should also have a check engine light lit as well its in "bulb check" mode at this point..

Suck, squish, bang, blow. You don't seem to have checked anything except fuses, and I really hope you didn't throw $2-300 worth of battery and alternator at it for no reason at all?

Pull a spark plug and check for ignition spark, remove the wire pull the sparkplug reconnect the wire and hold it (by the wire) against a grounded bit of metal like the head/exhaust (useing a wire to provide ground, like your jumper cables is alot easier safer and less accident prone, fwiw). When you turn the key to start you should see the ignition spark. You will/should also hear the piston pumping air out the sparkplug hole, you might even get some fuel spray.

Now find the pulse damper on the fuel rail, it has a small screw which protrudes when you have fuel pressure.

Now you have verified almost all the requirements for your engine to run. You have spark, you have fuel, and you have valves that move.. This leaves just valve timing as an issue (IE your timing belt may have jumped teeth)

 

Thanks for the reply. Yes usually the check engine is on too, but not since this happened. Only the three i mentioned come on when i turn ignition .. No i didnt.. Batt and alternator were bought by the seller. Lol. Dist, rotor, and wires all new as well.
ok ill check for spark now...

 

Ok if your CEL (check engine light) doesn't light up when you put the key to run that's a good place to start!

You need a volt/multimeter, it doesn't need to be a great one. They are $5-10 at your local import store like Walmart or harbor freight.

Check for battery voltage supply at the ECU. If you don't find power there work your way to the battery. Check the fuses, there are two exposed bits on fuses, you should have battery voltage on both of these exposed tabs. (Never trust your eyes to verify a fuse did not blow, fuses can fail in some cases and be completely "OK looking".

The next place to check is the EFI main relay, and after that the distribution block near the battery (junction block).


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If you have power to the computer you can test the CEL output at the ECU and see if it's just a bulb that failed coincidentally at the same time. (I'd have to double check to be sure, I recall it as switched power but it could be switched ground)

You need to Google and locate a factory service manual (FSM), it's your new best friend and will help you find all these test points.

 

Awesome. Ill start there and download that manual because i have no idea where these points to check are located. Got a voltmeter(im an electrician lol) .

 

uh .....

With the CEL (check engine light) not lighting at key-on, you've probably lost voltage in the EFI circuit. Test the fuses as co_94_pu suggests (ATC fuses have TWO metal tabs on top; check each for voltage to ground. This takes no time at all.) Do it with key-on (no voltage to the EFI fuse with key-off.) Find the diagnostic connector (next to the under-hood fuse box). Check for voltage to ground at B+ (with key-on). Only if you have voltage there do you need to progress to the ECM itself. While you're standing there, jumper B+ to FP; this forces the fuel pump to run with key-on. You SHOULD be able to hear it. (I have no trouble hearing the pump standing at the diagnostic connector with the truck in the garage; by the side of a busy highway it might be harder).

 

Ok ive located and accessed the ECU but don't know how/where to test for voltage there. I retest my fuses, all have continuity, only 3 of 6 have 12v going through. (EFI, Dome, and Haz-Horn) The charge(7.5) and two labeled head(10) have no current through them with the key on. Is this normal? Also, some progress i guess- while fiddling with the wiring removing my glove box around the ECU, my check engine light came on. I tried starting it and it almost started before the light went out and then just cranked. Truck also has some idling issues ( bounces up and down between 1.5 and 2 periodically and idles high). from what ive learned, maybe a bad ECU? Can you instruct me on how to test the ecu and / or power to it please? Also just read the last post, still have voltage to EFI with key off. I do have Voltage to B+. Also i can hear the fuel pump when i jump it.

 

You moved some wires and your CEL came on? That's a loose connection somewhere, maybe power maybe ground maybe just the cel in the dash harness. Intermittent wiring glitches are so much fun..

There are two power inputs to the ecu. Battery constant (batt, supplied directly from the efi fuse), and switched battery (b+, supplied from the efi fuse through the efi relay). In the 95 era book I'm looking at these are both on ECU connector A, pin one is b-g and supplying Batt, pin twelve is w-r supplies b+.
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I'm definitely not looking at the right year FSM, so take this all with a grain of salt..

In the manual I'm looking at the alternator is energized via the IGN fuse (might be charge in an older book), which is supplied via ig1 (ig1 & ig2 are important) off of the ignition switch. There some pretty consistent issues with the contacts in that switch. (That switch is a spring loaded puzzle which could result in a game of hide and seek, but you can clean the contacts up and get some more life out of it.)

Start with clean tight grounds, there is one in each kick panel as well as a few under the hood. There is a thread with good pictures for the grounds.

Next maybe wiggle wires at the connectors and if needed tighten up the female side of the lugs. Make sure they are all fully seated also. (These get spread out when someone jams a meter lead into them instead of beside them, a big nono)

Now hopefully you can wiggle the harness and not have intermittent connection, but if they were jaming probes into things they were probably looking for a wire break which you might have found somewhere in the harness behind the glove box.


​​​​​​​... Your idle is a separate issue ignore it for now

 

Lol oh yeah, loads of fun. Ok idle ignored. Ill get on to the testing tomorrow its dark out now and about 25 degrees. Thank you so much for your help so far. Ill post tomorrow when ive made some progress