1992 Toyota Pickup 3.0L 4 x 4 Manual trans. Truck died and after I got it home, I started to diagnose. Fuel pump not coming on either through ignition or shorting the diagnostic pins. Fuses are fine. EFI Relay checks out and energizes when 12V applied externally as does the Circuit Opening Relay. The check engine light does not come on either whne turning the ignition on or when shorting the diagnostic pins.

Here is where I am totally stuck. I get power from the ignition switch to the 7.5 Ign. fuse, but the power does not continue to pin 3 of the EFI relay and that is where I am stumped. No power to pin 3 means the relay cannot energize. I am not sure that the wire is a direct run from the 7.5 ign fuse to pin 3 of the EFI relay or it goes through the ECM. I have been searching for a Complete wiring schematic showing all wiring, but have not been able to find one. Any help, thoughts or suggestions greatly appreciated. TomC

 

I forgot to mention that the COR does click when the ign switch is turned om

 

Does the truck have spark?

If not, that means you may have a bad wire somewhere

 

To be honest, I am not sure. I have been concentrating on the fuel issue. Also, from what I read, if the ECM does not see fuel pressure it will not send info to the ignitor to create spark - yes - no?

 

Maybe these will help......

http://personal.utulsa.edu/~nathan-b...95efimainr.pdf

See pg. 17
http://www.lovehorsepower.com/MR2_PDFs/LWIRDIAG.PDF

When you say the CEL does not come on, do you mean it does not illuminate at all or that it simply does not flash a code? Just asking for distinction. .

 

The ECM has no way to "see fuel pressure" on these vehicles. Even if the fuel system entirely failed (ie. no fuel at all to the system) it would still create spark. That's controlled by the igniton circuit.....which the EFI main relay is definitely a part of.

http://www.autoshop101.com/forms/h23.pdf

 

thook - Thank you for the links. The CEL does not come on at any time - either when first turning on the ign switch or when shorting the diagnostic pins.

 

That first diagram is the one I used to check the fuel system components. With the ignition switch set to "on" I get proper voltage coming into and going out of the 7.5 Amp IGN fuse. BUT, I get no voltage at the relay coil. What I am not sure of is where the output of the 7.5 AMP IGN fuse travels through before it gets to the relay.

Thank you
TomC

 

Okay, then. Thanks.

I think what DC says is probably what's going. Start running from the 7.5 fuse and checking where the voltage is lost. IOW's, since it's a direct wire from the fuse to the relay, either your ground is bad or a wire or terminal is broken.

 

Crap. And I don't remember where the fuse is located offhand. I'll have to go out and look at my wife's vehicle.

 

I'm not understanding how a ground can be involved. I check the output of the fuse and I have the correct voltage. I pull the EFI relay and check the input voltage at the coil input pin with a reference direct to the negative battery post and I get nothing. Where would I be looking for a bad ground in this case?

Also - what does IOW stand for - (blush)

 

The IGN fuse? It is in the fuse block by the drivers kick panel.

 

Pin 2 is ground. Without a ground you won't get a complete circuit and therefore no voltage. But, if you're checking directly at the battery ground, then certainly that's a different situation.

You'll have to forgive me because I'm not recalling how it's all wired offhand. It's been a while since I've looked at my wife's vehicle for anything of this nature. But, I am going to look at it here in a bit.

IOW = In Other Words

 

Okay. That's what I thought. But, doubt had me thinking it might be in the main fuse box under the hood for some reason.

 

Yes, I was testing direct to battery, but also tested pin 2 direct to Battery Positive and it is also fine. So, somewhere I am losing voltage from the output of the fuse to the relay pin?? I took the main fuse/relay block off from the fender well and traced the relay pin 1 wire to under the fender and back through to the Passenger foot well behind the kick panel) and there is where I can no longer see the wire (Black with Yellow stripe).

 

I thought pin 2 was ground, but it may be pin 5 that's ground. Hmmm........better recheck my references. I can't check jack in this rain on the vehicle.

 

Not sure if the pick-up is the same as the 4Runner, but the Runner has another connection between the ign fuse and the efi relay. EB2 is the connector if the vehicle has rear ABS only located at RB#2 fuse block in the engine compartment or IB3 is the connector if the vehicle has 4 wheel ABS and it is located under the left kick panel.

 

If I'm repeating what others have already said, I apologize.

It sounds like you've tested the output of the 7.5a IGN fuse and found power (with keyon), and tested pin 1 of the EFI main relay and found NO power. The connection from the fuse to the EFI relay is a black w/yellow stripe wire, that goes through connector EA1 at pin 4 ("Cowl wire and engine room main wire, inside relay block 2").

I understand you've found the black/yellow wire. Have you tried tracing it back the the relay block, and back-probed the EA1 connector? Failing that, if you can find the black/yellow wire "near" the engine room fuse block, you could try pushing a pin into it to check for voltage.

Last but not least, you can try jumpering 12v up to pin 1 of the EFI relay, just to make sure that the relay closes. If the truck starts then you've identified the bad wire, or you can just check for B+ on the diagnostic connector (which needs the EFI to close to energize).

 

Oh, nice. Thanks for the back up, guys. I was admittedly at a loss.

 

I would like to thank all the folks that gave me advice/suggestions. I finally tracked down the problem to a loose/corroded connection under the main relay board.This one had me going in circles for a while.

Thanks again to all the great people that replied.

TomC