Real time help

[SteveLCetc]

If it was a fuel system thing why would the headlights cut out?

 

[pappy]

If it was a fuel system thing why would the headlights cut out?

What ever circuit is killing the lights is also killing the pump?

 

[TrickyT]

More info: The engine will run for 10 to 40 seconds before it dies (random). When it's running the alternator is putting out almost 14 volts. When it dies the headlights go out at the moment the RPM's start to drop (not after the engine has quit turning over).

If the headlights don't work it won't run, correct? Headlight circuit problem?

It's hard to believe that a problem in the headlight circuit would kill the engine. Instead, I suspect that the headlights are just being affected by the same root problem that's also affecting the engine. So you need to find out what electrical component is in common with the two.

If the headlights go off completely (not just get dim), then they are losing their +12v supply for some reason. And it sounds like when you lose +12v power to the headlights, you're also losing +12v either to the fuel pump or to the ignition or ECU. You should confirm the voltage loss to the headlights with a meter. If true, then measure other key points (like the +12v side of various fuses in the fuse block and the fuel pump relay) and figure out what all circuits are losing power. There's got to be some circuit in common with the headlights and the fuel pump/ignition/ECU. Once you know what all circuits are affected, looking at the EWD should point to the common component and you can then focus your troubleshooting on that.

Also, keep in mind that the various electrical circuits need both a +12v supply and a ground return. The problem may be on the grounding side.

 

[scottm]

Alternator alone seems unlikely, unless there's a dead short in it somehow. There would be a gradual loss of headlights, and a sputtering failure of the engine rather than sudden stop.

I vote connection on the starter or alternator. Is there currently power to the starter, but not the lights?

 

[Ruadhrigh]

Thank you all for the troubleshooting.


The fuel pump sounds reasonable, but my question is how does that relate to the low voltage? Either way I will remove the fuel pump and check its condition.

I am still waiting on the tow truck, but when the vehicle is retrieved I plan to install Onur's 6 mo. old alternator. It is a part that is fairly easy to access and will quell some of the charging questions. I do plan to take the old alternator to NAPA and get a quick bench test to see how it is fairing.

From there I will get to know Onur's FSM very well and hopefully I can find something in there.

for now I'll try to answer some of the questions...

 

[Ruadhrigh]

I would be looking for a grounding problem on the body side with all the above info.
You have 2 sources producing 12V on the postive side

during tear down and rebuild we were very careful to note all ground wires and the correct place for them, I am confident that grounds were replaced correctly. It could be possible that one has broken free, so I will be sure to investigate that.

Dan,
that sounds a lot like Doug's situation at DV. It was the actual fuel pump, removed thru the 2nd row seat port. The wire was frayed and shorted. Possible?

I plan to take the pump out. I am sure the FSM has a bench test to checks its operations. Since I have Onur's truck at my house I plan to scavenge some parts from it and this will be one of them...

for testing purposes

Just a shot in the dark, but could the fault be in the ignition switch/column wiring?

I will see what the FSM tells me about this system and test it out

Dan, just for the process of elimination, can you swap in another MAF and see if it helps? If it is not that I'd look almost exclusively at the fuel pump (pump, signal or wiring itself). Again, just for process of elimination it would take like two minutes to verify or deny that one possibility.

Though it seems unrelated, inspecting the MAF won't hurt or take much time.

I'll say one thing that I know is "right" with this problem is the group of fine folks you have with you to help here.

That is very true. I am lucky to have made friends with these guys. They were very helpful with the on-sight troubleshooting and very patient bringing her down the mountain.

That's the important thing, getting the truck and driver off the mountain. That's the nice thing about wheeling in the Toyota clubs. Other clubs may have left it and taken the driver home leaving it for him to get it down the mountain later.

Unfortunately the 80 spent the night alone in the woods. Very fortunately I didn't have to. But the club definitely would not have let me retrieve the truck on my own.

Pure guess; does it have an alarm system (ie: shutting things down)? That wouldn't explain losing the lights though; a head scratcher; why a complete intermittant power loss? Can you disconnect the MAF and see if it stays running (default limp home mode)??

The truck does have the factory alarm system.

Did you disconnect the harness from the glove box end? Maybe one of the connecters is damaged /not plugged in all the way?

Harness was never disconnected. But during head gasket troubleshooting I did ensure that the connectors were secure.

The three or four pin connector on the alternator has been known to cause some very strange problems, if memory serves.

If the connector is dirty, corroded, etc., it can cause ignition failure. Based on symptoms , this connector (with engine not-running) is in a correct connection position. As soon as the engine starts the vibration moves the connector/wires and poof goes the ignition, shutting down the engine.

...

I will check this before swapping alternators.

It's hard to believe that a problem in the headlight circuit would kill the engine. Instead, I suspect that the headlights are just being affected by the same root problem that's also affecting the engine. So you need to find out what electrical component is in common with the two.

If the headlights go off completely (not just get dim), then they are losing their +12v supply for some reason. And it sounds like when you lose +12v power to the headlights, you're also losing +12v either to the fuel power or to the ignition or ECU. You should confirm the voltage loss to the headlights with a meter. If true, then measure other key points (like the +12v side of various fuses in the fuse block and the fuel pump relay) and figure out what all circuits are losing power. There's got to be some circuit in common with the headlights and the fuel pump/ignition/ECU. Once you know what all circuits are affected, looking at the EWD should point to the common component and you can then focus your troubleshooting on that.

Also, keep in mind that the various electrical circuits need both a +12v supply and a ground return. The problem may be on the grounding side.

Very good advice. I will apply this when I have the truck.

 

[Ruadhrigh]

Do you have an OB reader/scanner with you?

I had the scan-gauge plugged in but there was not enough power for it to run.

 

[Ruadhrigh]

One issue not mentioned in Onur's summary is Rory was reporting low voltage at the dash gauge for a time prior to the truck cutting out.

The truck was running fine. I was jamming out to the radio, the heater was keeping my feet warm, CB was working fine, and the scangauge was helping me monitor temperatures.

I noticed a couple of times that the battery low indicator was coming on. I switched the scangauge to monitor voltage. It was a little above 11. I shifted into 2nd and then L to try and bring my RPMs up. The RPMs did not effect the voltage. The problem seemed to correct itself as the scangauge read 11.6 and the light was no longer on.

A while later I was behind Dan on a nice slick slope. I was idling while he attacked the slippery ascent. Then I noticed that the light was back and the CB had turned itself off. Voltage was 10.9. Since RPMs didn't help me the last time, I started turning things off the Radio, Heater, Wipers, and Headlights. All gave me a slight bump in voltage. When it was my turn to attack the slope I was gunning it and the truck stalled out. I immediately restarted it and climbed up to meet the rest of the group. I got out of the truck to help with a recovery of two sunken Cruisers, but left it running.

When I returned the truck was not running and would not start. We hooked up the battery to a 40 and tried jump starting it. No go. So we swapped batteries. The truck started up and I excitedly punched it forward. The truck died shortly after maybe 10 feet. We tried again with another battery and had the same results. After some unsuccessful trail-side diagnostics the snow had piled up, we were all cold and exhausted from the long day. So we decided to leave it for the night and attempt recovery with the daylight.

 

[Beowulf]

All the suggestions above are great and Rory has addressed all of the questions.

The following post in particular is right on target...

It's hard to believe that a problem in the headlight circuit would kill the engine. Instead, I suspect that the headlights are just being affected by the same root problem that's also affecting the engine. So you need to find out what electrical component is in common with the two.

If the headlights go off completely (not just get dim), then they are losing their +12v supply for some reason. And it sounds like when you lose +12v power to the headlights, you're also losing +12v either to the fuel pump or to the ignition or ECU. You should confirm the voltage loss to the headlights with a meter. If true, then measure other key points (like the +12v side of various fuses in the fuse block and the fuel pump relay) and figure out what all circuits are losing power. There's got to be some circuit in common with the headlights and the fuel pump/ignition/ECU. Once you know what all circuits are affected, looking at the EWD should point to the common component and you can then focus your troubleshooting on that.

Also, keep in mind that the various electrical circuits need both a +12v supply and a ground return. The problem may be on the grounding side.

I think Tom's above analysis is correct.

A couple of other points and/or questions.
* When the truck shuts off, it is as though the ignition was turned off... It just stops dead... Well, this points to ignition switch right? Nope. The lights go off immediately (not dimming, OFF.) Try this on your truck. Turn on the lights then switch off the ignition with the door closed. Lights remain on until you open the driver's door. Therefore, I do not think it is in the ignition switch.

* When the truck shuts off and the lights turn off, the shift interlock is tripped. What causes the shift interlock to trip? Bad taillight? Bad ground? OK, but why does the truck start 2 minutes later and runs fine for ~30 seconds? A broken taillight won't "fix" itself and an intermittent ground wouldn't fail every 30 seconds.

* Regarding the headlights... It is important to remember that the 80-Series headlights always have +12v. They are switched on/off with the ground side of the circuit. Again, this points to something that would cause a relatively predictable loss of the ground circuit. (By predictable, I mean not like a ground strap that came loose... otherwise it would be completely dead and the headlights would never come on.)

* Why does the truck "heal" itself. Hell if I know, but it sure points to some type of relay that gets triggered due to something. This "self-healing" really has me puzzled. Kinda points to some timer based do-hicky or something heat related but we cannot come up with something to test. As to the "heat related", we approached a completely frozen truck (literally frozen), put the jumper cables on it, it started and ran for ~30 seconds, then stopped. Same symptoms when it was hot.

* The suggestions to look at the security system are excellent (thanks gray and Doug.) Problem is that the security system is not documented in the EWD or the FSM. I have an EWD for the RS3000 alarm but, unfortunately, it didn't make the trip up the mountain with me.

* We tested many circuits for +12v. That is fairly easy to test. Testing for loss of ground is not easy. Especially outside at 10,000' in the dark and snowing.

* The 3 clues that seem relevant to me are:
...1. the headlights and dash lights turning OFF (not dimming), simultaneously with the engine shutoff.
...2. the shift interlock. That is a major clue that we have to follow up on. AFAIK, no security system engages the shift interlock. (Yes? or No?)
...3. it "self-heals" after a short time and starts up OK.

-B-

 

[Beowulf]

Another question for the experts...

How long does the ECM wait for the "Alt Good" signal?

Where I am coming from is maybe the Alt is OK (14v at Batt) but we know there were some corrosion on the connectors and we "fixed" one of them. If the "Alt Good" signal doesn't get to the ECM then maybe the computer says... "I will wait 30 seconds and if I don't have a good alt signal then we're shutting down the ECM, the fuel system, the lights, and everything else." Plausible?

-B-

 

[medtro]

It's hard to believe that a problem in the headlight circuit would kill the engine. Instead, I suspect that the headlights are just being affected by the same root problem that's also affecting the engine. So you need to find out what electrical component is in common with the two.

If the headlights go off completely (not just get dim), then they are losing their +12v supply for some reason. And it sounds like when you lose +12v power to the headlights, you're also losing +12v either to the fuel pump or to the ignition or ECU. You should confirm the voltage loss to the headlights with a meter. If true, then measure other key points (like the +12v side of various fuses in the fuse block and the fuel pump relay) and figure out what all circuits are losing power. There's got to be some circuit in common with the headlights and the fuel pump/ignition/ECU. Once you know what all circuits are affected, looking at the EWD should point to the common component and you can then focus your troubleshooting on that.

Also, keep in mind that the various electrical circuits need both a +12v supply and a ground return. The problem may be on the grounding side.

In fact, headlights off when engine is shut down, i.e. ignition off, is a safety feature. Now, why did the engine shut down without having to turn the ignition key off is another story.

 

[cruiserdan]

...2. the shift interlock. That is a major clue that we have to follow up on. AFAIK, no security system engages the shift interlock. (Yes? or No?)


-B-

I think that is a by-product of the power loss to the lights. If a brakelight bulb is out or if the brake light fuse is blown the interlock will not operate when the brake pedal is depressed because the interlock gets the signal from the brakelight circuit.

 

[EricG]

Another question for the experts...

How long does the ECM wait for the "Alt Good" signal?

Where I am coming from is maybe the Alt is OK (14v at Batt) but we know there were some corrosion on the connectors and we "fixed" one of them. If the "Alt Good" signal doesn't get to the ECM then maybe the computer says... "I will wait 30 seconds and if I don't have a good alt signal then we're shutting down the ECM, the fuel system, the lights, and everything else." Plausible?

-B-

Seems strange - this would mean that it would be impossible to run a truck with a bad alternator, right? As in limping a few miles on the battery. I've never done it on a cruiser - but plenty of times with my old camaro that ate crappy rebuilt alternators for breakfast.

Anyway, good luck guys. This crap can never happen in the parking lot of the grocery store next to the NAPA shop, right?

 

[sleeoffroad]

Have you guys checked the connections to the batter. We have seen that corrosion builds up between the different ring terminals and actually make the center ones loose contact. Swapping batteries might cause it to move a little and make contact. Check all the individual ring terminals on the fusable links.

The truck will run without alternator output until it is to low to run the ECU (which I believe is about 10v). At that point it will die.

 

[Beowulf]

Have you guys checked the connections to the batter. We have seen that corrosion builds up between the different ring terminals and actually make the center ones loose contact. Swapping batteries might cause it to move a little and make contact. Check all the individual ring terminals on the fusable links.

The truck will run without alternator output until it is to low to run the ECU (which I believe is about 10v). At that point it will die.

Christo,
One of the tests we ran was to put + connection from Ali's battery (engine running) to the junction point after the fusible links (with jumper cables) so Rory's truck was guaranteed to be "seeing" +14v. It ran ~30 seconds and died. We decided that eliminated the alternator, battery connections, fusible links.

Yes, we checked the battery connections. They should be checked again though. I don't remember if we checked the connection points after the fusible links.

-B-

 

[Beowulf]

In fact, headlights off when engine is shut down, i.e. ignition off, is a safety feature. Now, why did the engine shut down without having to turn the ignition key off is another story.

I believe you can test this on your truck and you will find the headlights will stay on after the ignition switch is turned off (until you open the driver's door.)

-B-

 

[medtro]

I believe you can test this on your truck and you will find the headlights will stay on after the ignition switch is turned off (until you open the driver's door.)

-B-

I did before I posted that

 

[Beowulf]

Seems strange - this would mean that it would be impossible to run a truck with a bad alternator, right? As in limping a few miles on the battery. I've never done it on a cruiser - ...

Agreed. This is another reason we didn't replace the alternator even though we had one ready to be put in (fairly big job in our conditions and with 30 minutes of daylight.) We could simulate a good alternator when we jump started because we would leave the jumper cables attached to a truck with a good alternator and it would still die. That was why I asked about the "Alt Good" signal because in this test, that signal to the ECM would be coming from the disabled truck's alternator. (I hope this paragraph makes sense.)

-B-

 

[cpg]

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?

 

[Beowulf]

I did before I posted that

Are you saying that your headlights turn off if you turn off the ignition?

I just went out and tested my '97 and it behaves as I described. Start the truck, turn on headlights, turn off ignition, headlights remain ON, open driver's door, headlights turn OFF.

Yours is different?

-B-