Yesterday I was driving down the road doing about 30mph and my 4Runner just died. Without warning or a shudder, it just turned off. I threw it in neutral, turned the key, it cranked up and then immediately shut down. I coasted into a parking lot and turned it off.

Here is what happens:
ò When I turn the ignition key, it turns on for a second and then immediately shuts back down.
ò Battery is good
ò MAF sensor and all cables are plugged in

I had it towed to a mechanic and he said
ò Fuel Pressure at the injectors is good
ò It has a spark when he turns it on
ò There are no fuel blockages
ò Yes, there is gas in the car
ò NO error codes/no check engine light
When you hold the key in the start position, it cranks and then dies within a second. It's like you turn it on and immediately turn it off. That's IT. ?!?????

I just had the timing belt replaced about 2 weeks ago and it has ran flawlessly. It ran great beforehand too.
Any ideas? I told my mechanic that I would post some of the things we tried and hope to help him.

Scary thing is my mechanic is stumped and I would hate to have to bring it to a Toyota dealership.

PLEASE HELP!!!

Did the person who did your timing belt job put the intake hoses on nice and tight, if they leak the engine will shut off...

A couple of possibilities.....

Could be a problem with the fuel pump relay control circuit.. When the ignition switch is turned to the start position that momentarily overrides a safety circuit to start up the fuel pump...

As soon as the ignition switch goes back to the run position, the fuel pump continuing to run is dependent upon the safety circuit which keeps the pump running ONLY if it sees that the engine is running...

There is a relay on the 3rd gen 4Runner in the under hood fuse panel that is labeled EFI relay.. With the vehicle not running you might pull this relay out and reseat it a couple of times to make sure it's making good electrical contact. This relay is powered from the main ECU which keeps it closed until the computer has determined that the engine is not running.

How did your mechanic check the fuel pump pressure? Was he able to keep the engine running and see if the pressure held when the problem reoccurred (assuming it would happen while he was testing). Wondering if the fuel pump pressure dropped causing the engine to shut down...

btw the fuel pump safety circuit is there for an extremely good reason. If you were in a collision with major damage that broke a fuel line anywhere from the fuel tank up to the engine, the tank mounted electric fuel pump would keep running and dumping fuel on the ground/engine compartment if the safety circuit wasn't there to detect that the engine has shut down.. Not a good situation to be in with someone in the vehicle with injuries or unconscious.


Next possible problem area the ignition switch, AM2 fuse or AM2 circuit wiring..

Have you tried jiggling the ignition switch when it starts to shut down (w/o hitting start <img src="/forums/images/graemlins/shiner.gif" alt="" /> <img src="/forums/images/graemlins/zombie.gif" alt="" /> ? (thinking that if the switch was getting intermittent you might be able to keep it running with the jiggling...)

The AM1 AND AM2 circuits pass through the ignition switch as shown below.



The engine ECU, fuel pump and ignition are all powered through the 30amp AM2 fuse, so any problem in this circuit would cause the engine to shut down.. Also pull and check carefully the 20amp EFI fuse.. It's the one that powers the fuel pump.. Since the ECU is not logging any codes during this failure, it makes me think that it, and the rest of the stuff on the AM2 circuit could be losing power when the problem occurs.

Check both the AM1 and AM2 fuses to make sure the fuse element hasn't cracked and reseat them several times to make sure they are making good contact.

Since the timing belt was just changed might also check the wiring coming from the crank angle sensor just to make sure it wasn't damaged while changing the timing belt.. Although I'm pretty sure this would set a code it the sensor/wiring was intermittent.

Thank you VERY much for the detailed response along with the diagram. I appreciate it!

come to find out, my crappy K&N air filter allowed some piece of trash through and it wrapped around one of the MAF sensor wires. Yep, that was all it was. I guess IÆm glad it happened in town then when somewhere out in the middle of nowhere.

Lesson learned. I have had nothing but trouble since i installed that air filter with it coating my MAF sensor with oil and then making my acceleration lessen. I'm changing to something that does not require any oils.

Thanks again!

I've heard nothing but good things about amsoil filters.

Get a TrueFlow filter much better in coustruction and longevity.....

I had this exact same problem about 2-3 years ago on my 2000 4Runner. I would start it up, and almost immediately, it would shut off, as if the fuel were cut off. Even if I gave it gas immediately after starting up, it would die as soon as I let go of the accelerator. This would happen intermittently, so it was quite frustrating, especially when it would happen when I was far away from home. At first, when I took it to the dealership, they said there was nothing they could do unless I could replicate the problem, but sure enough, as I was about to leave I started it and it died right in front of the service advisor (what luck!). It turned out to be a faulty THROTTLE POSITION SENSOR (TPS). It was replaced, and I haven't had the problem since (2+ years). Hopefully cleaning the MAF will do it for you, but if the problem comes back, you might want to test your TPS.

On a side note, I had my 4Runner shut down while driving just like you tonight. The check engine light came on while I was on the highway, and as I got off, I was cruising about 30 MPH when the engine just completely shut off without warning (RPM went to 0 and all warning lights came on) and I coasted (luckily, safely) to the side of the street to a stop. I was able to restart it, and it seemed to run OK, but the check engine light is still on. I'm going to try and clean the MAF and throttle body tomorrow, but I think there's a good chance I may need a new O2 sensor (hasn't ever been replaced). Please keep me posted if you solve your problem.