Electrical Issue... I think?

[80Series93]

Ok so my fusible links look nothing like the ones in the picture above... They don't even look like fusible links. I have the black box close to the battery and then it looks like just 2 wires that run from that down somewhere. There's only 2 wires from the battery to this black box as well.

The EFI relay was getting hot that's why I replaced it. I read a lot about that. So far all I've done is replaced that relay and a few fuses and checked some of the wiring under the dash and up near the battery. I wasn't to sure where else to go and I've been a bit stuck for time.

As for the CEL - it's never illuminated since I got the car. When it wants to start I get all the other warnings in the dash but no CEL but I starts. When it cuts out and won't start I get no response at all from the instruments/warning lights except the hand brake light and the volt gauge moves up.

the pics are bad but like I said before there's 2 wires which run from the positive terminal to that black box which are relatively short. And from that black box there's 2 thicker wires running out the other end which go down and into what looks like some sort of loom. It's running at the moment so when it dies I'll try fiddling with that box and the wires near the battery and see if it makes any change.

The picture of the dash with lots of lights is what I get when it will start and then the other picture with hardly any is what I get when it cuts out and won't start.

- B

 

[80Series93]

I've just realized I'm an idiot and I was looking in the wrong spot. Will check it out again tomorrow.

- B

 

[80Series93]

So after some testing today I've found that I have power after the fusible links when the car dies, but I have no spark. No power to the coil after it dies.

Where does the coil get its power from?

- B

 

[jonheld]

Ok so my fusible links look nothing like the ones in the picture above... They don't even look like fusible links. I have the black box close to the battery and then it looks like just 2 wires that run from that down somewhere. There's only 2 wires from the battery to this black box as well.

The 2 wires from the battery to the "black box" are 2 of the 3 fusible links. There is a 3rd that goes to a connector that can be seen in one of your pictures.
+12 for the ignition coil comes from the ignition switch which in turn is fed from one of the fusible links. This +12 is also common to the hot side of all injectors.
There is also a connector (EA2 or EA3 depending on the year) close to the fuse box on the left fender. This is the main engine harness and +12 from the fusible links pass through this.

 

[80Series93]

Well I've replaced the fusible links today and still having the same trouble.. I guess I'll try another ignition switch and see if that helps any.

- B

 

[jonheld]

This is a pretty simple circuit to test. I suggest a diagnostic approach rather than throwing parts at it.

 

[80Series93]

What do you suggest as a relevant diagnostic step? All I've found so far is that after the engine dies I have no power to the ignition fuse in the fuse box and no power to the coil, meaning no spark. I have power everywhere else. I've replaced the fusible links and the EFI relay and I've tried another ECU in the car. I have fuel and the fuel pump is operational when I turn the key on. I don't have a scan tool I can use on the car to check for any error codes etc. it runs perfect when it is running. Doesn't cough or splutter when it dies just a solid cut off.

If the symptoms don't narrow down the issue somewhat I'll book it in and have someone look at it. I don't really have the time to keep going with it, I work long hours. I was just hoping to save myself some money.

- B

 

[jonheld]

What do you suggest as a relevant diagnostic step?

Follow the circuit in the FSM with a meter.
Battery/fusible link/connector EA2 or EA3 depending on the year/ignition switch
If +12 is making it to the ignition switch, then test if it is making it out.
If +12 is not making it to the ignition switch then the problem exists upstream.

 

[80Series93]

Seeing as I have no power to distributor, coil or ignition is it safe to say that the issue could be with the AM1 link? Even though I replaced the link itself I didn't replace the fuse looking part in the fuse box under the bonnet...

 

[80Series93]

I also have power at the ignition switch and leaving the ignition switch. I have power at the fuse panel under bonnet. Everything else works, lights, radio, etc. and I obviously have power to the starter because it will crank. But no power at coil, no spark. No power to the 7.5A ignition fuse. I do have power to the IG-ECU fuse.

 

[jonheld]

There are 3 fusible links and each one feeds a different sub-system within the vehicle. This should be easy to trace with a meter. The suspect is AM2 or the connection from AM2 to the ignition switch or the ignition switch or the connection from the ignition switch to the rest of the system.

 

[jonheld]

There is also a splice point I6 from the ignition switch to the rest of the system. Hard to say where the exact location is according to the FSM, but it looks like it lives in the main harness that runs on top of the dash. Follow the ignition switch harness.
I would start by checking continuity from the ignition switch harness to the IGN fuse.
You obviously have a bad connection somewhere in the system and there's just not that many places it can be.
You're not blowing fuses, so we're not looking for a short, we're looking for an open.

 

[bloc]

What year is the above diagram for? black/red on injector circuit in US is OBDII per my diagrams.

systematic troubleshooting approach:

check for + at downstream side (chassis, not battery side) of fusible link
If good, pull AM2 fuse and check for + on one of those terminals
If good, check for + on White/red at EA2 connector pin 3 under fuse block
If good, move to ignition switch and check for + at white/red wire pin 3
If good, turn ignition on and check for + on black/green at ignition switch pin 4 (this changed to black/red on later trucks)
Finding I6 isn't worth it (yet).. it'll be coated in rubber and sealed in tape. Only bother with this if you find a problem with one leg of it. That said, the correct EWD will tell you exactly where it is located. In US trucks it is buried in the 2"-thick dash harness well behind the instrument cluster.
Move to IH1 behind ECU/glove box, check for + at pin 14 black/green. Then the black/green on each injector plug.
Move to interior fuse block. Check for + at one side of the "IGN" fuse when pulled.
Move to engine bay. Check for + at pin 7 black/green of EA2 (NOT pin 8, which is also black/green on the chassis side). If good check for + on black/green of ignition coil
Check for + on black/green pin 3 of ignitor.

Where you stop getting + in this system if you go from one end to the other following the circuit path will tell you exactly where the problem is.


All of that said, an Australian rig might have different wiring colors or connector names and locations, but the process is the same. Toyota's electrical wiring diagrams are fantastic.. in the section that has the engine control picture above, there is an index that says exactly what connectors get used, what page to find their location, all splices, descriptions of how systems should act, an index of what voltage should come across what wires under specific conditions..

 

[80Series93]

Thank you gents. I will have another look and do some more testing tomorrow. And thank you twice Jonheld, that first diagram is exactly what I've been looking for.

I can at this stage positively say I have no power to green/black at ignition fuse, no power to green/black at the coil. I will check igniter tomorrow and have another look at the ignition switch. I don't recall seeing a green and black wire at the ignition switch but I didn't take a great deal of notice. On the ignition switch today I had power at the red and and white wire and also a blue wire.

I appreciate your patience with me and all your info. I am a lot further now than I was a week ago.

As a side note - any idea where to find a new ignition switch? I'm having trouble. Even online. From what I have found they are not all that expensive and mine looks as if it's been tampered with at some stage so I wouldn't mind replacing it anyway.

- B

 

[80Series93]

So when the truck cuts out I have no power to the ignition switch from the red/white wire. I have power to the link in the fuse box in the engine bay so I'm guessing this tells us the issue is between that link and the ignition switch. I'm a little confused about this EA2 connector. Any chance you could elaborate or maybe give me a better indication of where I can find it? I've looked around the battery and the fuse box but can't see any red/white wires there.

Thanks

- B

 

[jonheld]

Ignition switch power wire from the fusible link is white with a red stripe.
The connector between the fusible link and ignition switch is either EA2 or EA3, but it remains a white wire with a red stripe from end to end.
You are going to have to trace this out. Unfortunately I don't have the EWD/FSM for a 1993 in front of me, but both the 1991 and 1997 specify that EA2 and EA3 live on the left fender and both are called "cowl wire and engine room main wire". It just can't be that different on a 93.

 

[80Series93]

So what exactly am I looking for...? is this in the engine bay I'm looking? Am I just looking for this red/white wire?

- B

 

[80Series93]

Today the truck did something new. When it went to cut out and die like it has been, all the warning lights flashed up on the dash and it kept running. It sort of stumbled for a minute and went to turn off but picked itself back up. I turned it off and went to start it again though and I had nothing. Don't know if that helps any or has any relevance.

- B

 

[bloc]

Yes engine bay. On a US truck EA1, EA2, and EA3 are all under the engine-bay fuse block.

As mentioned, find an electrical wiring diagram. In it is a page that shows what each connector looks like from the end so there so there is no confusion.

 

[alia176]

the attached PDF file is for my '96 but it may help the OP!