Need more help tracking down electrical issue.....

[Higgin]

Need more help tracking down electrical issue. UPDATE: PROBLEM FOUND....WITH PICS

Ok, so I think I am making some progress here on finding my elec. gremlin causing a crank/no-start issue. I have no CEL with key to "ON", no fuel, no spark. See post https://forum.ih8mud.com/80-series-...ks-but-wont-start-after-drivng-few-hours.html for the basics on what exactly happened.

If someone has some input on this, please open up you FSM to pg EG-235 and walk through it with me......

Ok, so, the ECM is not powering up since there is no CEL. The first thing I did was to jump over to the Toyota dealer and order up a set of fusible links. The old tested out fine, but looked very beat up, so thought I 'd try that first. So put them on, and nothing changed. Checked the EFI relay and fuses, they all checked out OK by my OHM/volt meter according to the FSM. I even picked up a spare EFI relay at the junkyard to double check that too.

So today I decided to start diving deeper. I started on page EG-235 of the FSM and started doing the voltage tests on the ECU itself to help isolate where the problem is. Well, first step is check BATT-E1 connection. It is supposed to be 9-14 volts with the key ON or OFF either way. I'm getting a reading of 5.3V KEY OFF and only 1.56 KEY ON. It is waaaay off. So this is probaby where the problem lies. But i went ahead andran the next few tests any way......IG SW-E1 was ok @12.16V, MREL-E1 was ok @10.7V. 4th test of +B-E1 also failed and came up the same 1.56V with the KEY ON.

Now, correct me if I'm wrong......So, I am assuming that since the 2nd and 3rd tests came out ok, and all 4 of these tests per the FSM use the ECM ground (E1), the ECM ground is ok. And, since tests 1 and 4 both failed, but had equal Voltage at the ECM, that should rule out the EFI Main relay as the culprit since test #1 goes directly to the ECM and #4 goes through the EFI relay.

So, if I am reading this right, according to the diagram in the FSM on pg EG-235, my problem must lie between the Main Fusible Link (which is brand new) and where the line splits to go to the EFI Main Relay. That has the 15A EFI fuse inbetween. I checked that fuse with an OHM meter weeks ago, but I'm going to throw in a new one tommorow just to be double sure.

So, what should my next step be? My guess is that I need to start testing voltage Staring at the fusible link and work my way back to the EFI fuse, and then from there to the EFI Main relay since they should be right there next to each other. Does anyone know exactly where the line comming from the EFI fuse splits off (with one going to the ECM, one to the EFI Relay)? I assume somewhere below the main fuse box. Can it be removed to check the lines under it?

So any ideas? Does this sound like maybe the EFI fuse really is bad? Dosen't make sense to me as a little voltage is getting through. Or do you think it is maybe just a bad connection or a chaffed wire somewhere? Just seems very odd that it is getting just a little voltage (1.56 volts) and not just nothing...... Or am I just toally off on my thinking and it could be something else entirely????

Sorry for the super long post, but I feel I'm getting close to solving this mystery and I pretty much suck at electrical stuff. I feel very good getting this far and I am learning tons! Thanks in advance for any help or pointers!

 

[96r50]

Sounds similar to the headache I had tracking down my intermittent no start. I learned a ton about 12v electrics from that experience.

In my problem I also experienced a voltage drop over the course of a circuit. I metered the circuit out piece by piece to find the source of the drop. It turned out to be corroded wire splices in an OEM connector, so don't rule those out. It sounds like you have the right idea of breaking it down into small pieces and checking them out one by one. Eventually you should find the point where the voltage drops off.

Do you have the EWD for your truck? It makes identifying wires and tracing circuits 1000 times easier.

Good luck!

 

[Higgin]

Yes, I have the EWD. But it is very very confusing for me. I hardly know peep about tracking down electrical problems. I even had to ask how to properly use the Volt/ohm meter, lol. But I am gaining knowledge, thats for sure!

 

[greentruck]

Hang in there. It's like algebra, makes my head hurt, but I'll do it if I have to.

I agree you're on the right course. Think of the EWD as an indicator of possible trouble points. It tends to be descriptive of what connectors do what, vs the diagrams and decision trees which show how things interact electrically.

It's like the difference between your PC or Mac and the Internet. Or the one is Expedia while the other is your GPS.

Look over the stuff in the EWD about locating connectors and pin outs. That's where corrosion or whatever can cause problems and where you can test to follow the circuits you've identified from the FSM.

 

[informationjunky]

don't forget to check the harness near the egr pipe.

 

[Higgin]

So I got up bright and early at 5:30am this morning so I could meet my friend at 7 to start working on finding the electrical gremlin that has had my Cruiser parked for the last few weeks. He's an electrical engineer, so I had confidence we could find the problem. We dug in, following the FSM and our hunches till we got it isolated to a short somewhere between the Main Fusible Link and the 15A EFI fuse in the underhood fuse box. Took us maybe 2-2.5 hours to get to that point. Mainly what held us up was that I had wrongly assumed that the fusible link by itself was the Main Fusible Link. Wrong! Its the one with the largest gauge wire that goes into the tinybox with the other fusible link. Up till we figured that little mistake out, we couldn't make heads or tales of what was going on.

Once we realized our mistake though, things started going pretty quick. We had to figure out where the short was in that line. According to the wiring diagram, that line comes off the Fusible link and goes right to the 15A fuse. So we first pulled the fuse panel up to look at the wire connections going to the 15A fuse. That looked good. So we then assumed that the short had to be somewhere in that line. So we started pulling the coving off the wiring harness starting at the fuse box and working back and going from the fusible link and going forward. Figured we'd run into the problem in no time.

So once we started peeling all the covering off, we realized that the line comming off the main fusible link dosen't go directly over to the 15A fuse in the fuse box like the wiring diagrams make it look. Turns out it swings over to the alternator where its crimped onto a fitting with another wire thats hooked to the alternator. That other wire is the one that goes back over to the 15A fuse. Once we started getting close to the alternator, which we hadn't paid any attention to up to that point, the problem jumped out at us.....the wires where they were crimped and connected up to the alternator were absolutely fried! I barley touched them and they basically fell apart off the crimped fitting. Seeing that, I could only think.....how the F had my truck run as long as it had??? They were totally destroyed.......here they are after they just fell apart off the fitting....

Here they are with the black covering removed.....

They were absolutely corroded and fried beyond belief! So then I tried to remove the nut holding the wire connector on the alternator...I barely put any force on it what-so-ever and snap......the little stud broke off the alternator. When I took a look at it, I couldn't believe what I saw.....the two nuts and wire connector and stud had basically welded themselves all together! Look at the remains of the wires where they were crimped on......can't even tell they were ever wires. Just a mess of burnt crap.

What we came with as the cause for all this was mainly that the little rubber cover that is SUPPOSED to go over that connection at the alternator to keep out the elements and keep everthing nice and shiney and looking new was never put back on when a previous owner had the alternator replaced. This caused the exposed copper wire (and all the metal pieces) to corrode over time and eventually lead to a resistance short....(the ecu was only getting 5.6V when we started digging in). This also (hopefully) explains my very random flashing dash lights. Not so sure what caused the metal parts to all weld themselves together??? Probably because of the short, I'm sure, but maybe faulty alternator??? Or amybe one of the nuts wasn't tightened properly??? Not sure. All I know....that alternator is outta there! I'm not chancing it.

So I went to the junkyard later today and pulled a toyota alternator (Manf. date 2007...nice!) off a cash for clunkers 94 LC and also pulled off enough of the wiring harness to hopefully fix the damage. I'm debating whether to just get the rebuild kit and rebuild my jukyard alt or just to get a new Toyota alt. The one from the junk is only from 07, but it looks like the hood had been propped open for a while now and the alt got wet and started getting some corrosion on it.....a little rust on the pully and some corrosion on the body of the alt. Not sure about the internals....And I am totally afraid of ANYcorrosion now. Anybody have an opinion on what I should use? I'm really leaning towards just getting a new one so I know I won't ever have to mess with it again.

Anyway, hopefully my baby will be back on the road late in the week. And heres a lesson for others.....ALWAYS replace any little rubber wire covers! They are there for a reason!! Now its time for some tacos and a few tasty beverages

 

[Higgin]

BTW - 96r50..........you were right on the money! Corroded wires splices at an OEM connection! Was this the same place it happened to you? Its amazing the amount of knowledge rolling around this website! IH8MUD ROCKS!!!!!!

 

[7schulz]

Good work my friend, maybe one of these days both of our truck will be working and we can do some wheelin. Lift and wheels should be on in Sept.