Real time help

[Ruadhrigh]

Sounds like a connector or wiring in the harness has a short or bad connection. Maybe when you did the head gasket you pulled on some not so good of shape connectors or wires?

I guess this is possible. Everything above the intake was disconnected. And I was sure to listen for the snap of the connectors when mating them. But still worth the investigation.




the update:

No new discoveries with truck, but it is finally home.

 

[TrickyT]

I looked over the 1997 EWD FSM and many if not all of the symptoms described by beno (post #34) and others can be explained due to a intermittent connection between the two white wires running to terminal "B" on the alternator. Look at page 52 - Power Source - in the EWD manual. +12v runs from the main fusible link on the battery through a couple of splice junctions to the alternator, then from the alternator through another connector to several fuses on the fuse block in the passenger compartment. If there was a bad connection between the two wires at the lug on the alternator, power might not be reliably reaching the fuse block. This would affect the ECU, headlights (because there's no power to the headlight auto off "retainer" circuit), shift lock (because there's no power to the stop light switch), and dash illumination (because there's no power to the tail light relay). This theory is easy to test. Next time the headlights (and, by association, engine) fail, move the headlight switch to the "flash" position (pull the lever towards you). This bypasses the headlight retainer relay. If the headlights light up, then power is reaching the headlight relay but not the rest of the circuits "downstream" of that, which includes that part of the fuse block powered by the "main" fusible link. If this is the case, then there has to be a break between splice E7 in the engine compartment and the fuse block, and the most likely candidate is the inherent splice on the terminal lug at the alternator.

 

[IdahoDoug]

If I shut off my engine with the headlamps on, my engine stops but the headlights stay on until I open the driver's door. True on both 93 and 97.

DougM

So, any thoughts about using starter fluid to see if it will still run?

 

[Beowulf]

This theory is easy to test. Next time the headlights (and, by association, engine) fail, move the headlight switch to the "flash" position (pull the lever toward you). This bypasses the headlight retainer relay. If the headlights light up, then power is reaching the headlight relay but not the rest of the circuits "downstream" of that, which includes that part of the fuse block powered by the "main" fusible link. If this is the case, then there has to be a break between splice E7 in the engine compartment and the fuse block, and the most likely candidate is the inherent splice on the terminal lug at the alternator.

Tom,
That terminal lug "B" at the alternator is the one that was corroded. We thought we had that covered with the jumper we put back to the battery. It is HIGHLY possible we missed something in that area.

" ... then from the alternator through another connector to several fuses on the fuse block in the passenger compartment. "

We did not check that wire. In fact, I'm not sure anyone saw that connection but there were several wires in that area and we could have missed that one.

Rory,
Run out and try the high-beam "flash" test if the truck is back at your house. I'm dyin' to find out if the lights come on.

-B-

 

[turbocruiser]

Rory,
Run out and try the high-beam "flash" test if the truck is back at your house. I'm dyin' to find out if the lights come on.

-B-

Yea Rory, the suspense is simply too much here, we gotta get an answer and I think that TT might really be on to something pretty specific. Sorry to pester but that's the way we are I suppose!?!

 

[EricG]

I looked over the 1997 EWD FSM and many if not all of the symptoms described by beno (post #34) and others can be explained due to a intermittent connection between the two white wires running to terminal "B" on the alternator. Look at page 52 - Power Source - in the EWD manual. +12v runs from the main fusible link on the battery through a couple of splice junctions to the alternator, then from the alternator through another connector to several fuses on the fuse block in the passenger compartment. If there was a bad connection between the two wires at the lug on the alternator, power might not be reliably reaching the fuse block. This would affect the ECU, headlights (because there's no power to the headlight auto off "retainer" circuit), shift lock (because there's no power to the stop light switch), and dash illumination (because there's no power to the tail light relay). This theory is easy to test. Next time the headlights (and, by association, engine) fail, move the headlight switch to the "flash" position (pull the lever towards you). This bypasses the headlight retainer relay. If the headlights light up, then power is reaching the headlight relay but not the rest of the circuits "downstream" of that, which includes that part of the fuse block powered by the "main" fusible link. If this is the case, then there has to be a break between splice E7 in the engine compartment and the fuse block, and the most likely candidate is the inherent splice on the terminal lug at the alternator.

Interesting ... what makes it work for 30 seconds and then cut out ... and then start again a few minutes later?

Only thing I can figure is that it's corroded - gets hot when the current hits it and somehow expands or increases resistance until it breaks the circuit. As soon as it cools - which is pretty quickly, being just a small wire connection, you're back where you started.

It's a theory

 

[dfmorse]

This is a helpful fuse chart:

http://homepage.mac.com/dfmorse/FuseChart3.5.1/

I just love this troubleshooting s*** on email - blah. Many great people are going to help to figure this out.

Below is a detailed point of view of my brain at this time period. 10Dec2007...

Based on the work all have done in the past threads; the conclusion is u have a very flakey alternator.

Let me explain said alternator;
assume diode packs are ok:

Alternator voltage rises to 16.768 volt as engine RPM goes over 1200rpm. Regulator shuts this voltage down to 14.78 volts (slowly) [I watch this daily on my system]
http://homepage.mac.com/dfmorse/RigProj/page1.html]

However- the workings of the alternator are a mystery..
Watch this; if the voltage out put of the alternator drops (internal problems-shorts-etc) , the total out put voltage across the buss (i.e. battery) will drop.
This could be alternator winding/stator failure. This could be in just a few seconds as the alternator heats up.


But;
Rectifier failure :
( This could be diode bank failure shorting on one or more Phases). This could (is) happening before any fuse system could react. This is internal to the alternator/regulator. There are no fuses inside the alternator that I know of. If the diode pack (or one of the diodes ) is in a fail mode, it could suck the alternator AC voltage down to below 8.13 volts. Below 10.15 volts, all most all relays in the FZJ80 series drop out (de-energize). Below 9.5 volts peak, the Major ECU says fxxx it, and drops the fuel ejection pump system (this is in the FSM). This is really hard to track. I suspect a diode pact fail symptom!!



I"ve been thinking too much. let us see if this helps the thread..

...

 

[OGBeno]

I looked over the 1997 EWD FSM and many if not all of the symptoms described by beno (post #34) and others can be explained due to a intermittent connection between the two white wires running to terminal "B" on the alternator. Look at page 52 - Power Source - in the EWD manual. +12v runs from the main fusible link on the battery through a couple of splice junctions to the alternator, then from the alternator through another connector to several fuses on the fuse block in the passenger compartment. If there was a bad connection between the two wires at the lug on the alternator, power might not be reliably reaching the fuse block. This would affect the ECU, headlights (because there's no power to the headlight auto off "retainer" circuit), shift lock (because there's no power to the stop light switch), and dash illumination (because there's no power to the tail light relay). This theory is easy to test. Next time the headlights (and, by association, engine) fail, move the headlight switch to the "flash" position (pull the lever towards you). This bypasses the headlight retainer relay. If the headlights light up, then power is reaching the headlight relay but not the rest of the circuits "downstream" of that, which includes that part of the fuse block powered by the "main" fusible link. If this is the case, then there has to be a break between splice E7 in the engine compartment and the fuse block, and the most likely candidate is the inherent splice on the terminal lug at the alternator.

THAT's IT Tricky T!

I know this is the reason for a couple of reasons....

When I snapped off the 10mm bolt at the alt., and we bypassed the wires that connected to the 10mm bolt, we only put one from the alt to the + side of the battery.

Looking closely at that wire that we bypassed, it is in fact two wires bundled together under there. I know this because I taped up that end that we bypassed because we didn't want it hitting the alt body and shorting the system out. Now I remember!

Rory--it's not the alternator. It's those wires going to the alt that are put on the bolt. Recommendation: cut back the taping, etc. on those wires, splice in two wires and reconnect to the 10mm/12mm nut/stud combo on alt and it should work. For now.

Order those wires from Dan tomorrow--it'll take a couple of days for those to come in and then we can put the new ones in ASAP.

I really do think this is the answer to the mystery.

-o-

 

[scottm]

That's got to be it! I don't see anything else that can carry that kind of current or that central to the power supply that could do this.

Doug, I've run an engine on starter fluid with no spark or fuel. It was maddening because I assumed I must have spark for it to run, but it was dieseling.

 

[cpg]

I guess this is possible. Everything above the intake was disconnected. And I was sure to listen for the snap of the connectors when mating them. But still worth the investigation.

No new discoveries with truck, but it is finally home.

I would worrie about the one under the intake the oone you did not unplug but moved around. I was thinking that because you found the alt connector so corroded.

 

[cruiserdan]

I looked over the 1997 EWD FSM and many if not all of the symptoms described by beno (post #34) and others can be explained due to a intermittent connection between the two white wires running to terminal "B" on the alternator. Look at page 52 - Power Source - in the EWD manual. +12v runs from the main fusible link on the battery through a couple of splice junctions to the alternator, then from the alternator through another connector to several fuses on the fuse block in the passenger compartment. If there was a bad connection between the two wires at the lug on the alternator, power might not be reliably reaching the fuse block. This would affect the ECU, headlights (because there's no power to the headlight auto off "retainer" circuit), shift lock (because there's no power to the stop light switch), and dash illumination (because there's no power to the tail light relay). This theory is easy to test. Next time the headlights (and, by association, engine) fail, move the headlight switch to the "flash" position (pull the lever towards you). This bypasses the headlight retainer relay. If the headlights light up, then power is reaching the headlight relay but not the rest of the circuits "downstream" of that, which includes that part of the fuse block powered by the "main" fusible link. If this is the case, then there has to be a break between splice E7 in the engine compartment and the fuse block, and the most likely candidate is the inherent splice on the terminal lug at the alternator.

Brilliant!

That really makes huge sense and puts a nice bow on the whole thing.

Waiting to hear back from Rory.

 

[Beowulf]

Interesting ... what makes it work for 30 seconds and then cut out ... and then start again a few minutes later?

... and ...

Based on the work all have done in the past threads; the conclusion is u have a very flakey alternator.

We may still have an alternator problem and that is why our testing did not work. We thought we were duplicating the function of the alternator by putting cables to another truck... but the wire that Tom pointed us to is getting voltage *only* from the disabled truck's alternator.

When we would put jumper cables to the truck the voltage would rise enough to engage the starter and power up the ECM (through the corroded connection) but after a few seconds there would not be enough voltage at "B" to keep the ECM powered up.

-B-

 

[Ruadhrigh]

Update:

I followed TrickyT's advice and looked at the wires between the alternator and the fuse box. All the wires in that loom look like they had faced some extreme temperatures. Very brittle and charred. My guess is the corrosion happened after the charring. Here are the pictures:

I am going to make a trip to NAPA and see what they have for crimp eyelets, and probably Radio Shack for the wire.

 

[Romer]

Sniff sniff, I love this place. Thats great troubleshooting even if it turns out to be something else.

Can't wait to find out.

 

[Beowulf]

I followed TrickyT's advice....

Please tell me you tried his suggestion for isolating the circuit by pulling the high-beam flasher after the truck dies and the headlights go off.

-B-

 

[TrickyT]

Update:

I followed TrickyT's advice and looked at the wires between the alternator and the fuse box. All the wires in that loom look like they had faced some extreme temperatures. Very brittle and charred. My guess is the corrosion happened after the charring. Here are the pictures:

...

I am going to make a trip to NAPA and see what they have for crimp eyelets, and probably Radio Shack for the wire.

Rory, What's the history with this truck? It looks to me like this problem has been brewing for a while. The brittle insulation indicates prolonged high temperatures in the vicinity of the terminal lug, perhaps from a high resistance connection that just got hot from the normal current load the wires carry. A couple inches away from the terminal lug (where your thumb is in picture #3) the insulation looks okay, so temps were lower there. It could even have been a loose nut connecting the terminal lug to the alternator and the lug just transfered the heat to the wires and insulation. Has the alternator ever been replaced? If so, maybe that nut didn't get properly torqued.

You also need to separate and inspect the other wires in that cable bundle, as they look like they could be damaged too.

Glad you found the problem!

 

[flintknapper]

So, in fact.... we DIDN'T do what was suggested in post #4?

"Look carefully at all engine wiring harness' for burn throughs (shorts)".

 

[Ruadhrigh]

Flintknapper,

I did exactly what was suggested by you in post #4. I did not even open the hood after I got it home last night. This morning I went directly to the wires that were removed from the alternator while troubleshooting on the trail. The pictures show what I found.


Beo,

I did not test the circuit as suggested. When I saw how bad the wires were I pulled the battery and battery tray for better access to the wire loom. A friend is going to bring me some wire later today. In the meantime I will pull the battery off the trickle-charger, put it and the tray back and isolate the circuit as Tricky suggested.

 

[Ruadhrigh]

Rory, What's the history with this truck? It looks to me like this problem has been brewing for a while. The brittle insulation indicates prolonged high temperatures in the vicinity of the terminal lug, perhaps from a high resistance connection that just got hot from the normal current load the wires carry. A couple inches away from the terminal lug (where your thumb is in picture #3) the insulation looks okay, so temps were lower there. It could even have been a loose nut connecting the terminal lug to the alternator and the lug just transfered the heat to the wires and insulation. Has the alternator ever been replaced? If so, maybe that nut didn't get properly torqued.

You also need to separate and inspect the other wires in that cable bundle, as they look like they could be damaged too.

Glad you found the problem!

The truck was down for a while while the head-gasket was replaced. The alternator was removed for that process and it is possible that the lug was not secured properly afterward.
I cut back all of the harness housing and inspected the wires. Further from the lug the insulation is soft and flexible. Towards the lug the insulation is brittle and mostly cracked. I isolated the wires from each other by wrapping them with electrical tape. This is not my permanent fix, and I will be replacing them with new wire. I will either splice into the harness and solder the new wire to the old, or chase the wires to their other terminations and replace the entire wire.

 

[pappy]

Rory,

You might have Onur or Dan look at the EPC and see if that piece of harness is a subharness that they could provide. I would rather replace a subharness, than fix/solder any day.