M42 died on the highway - Solved

[roguetoaster]

On startup at the start of the trip the cluster lights were lightly flickering, it quit doing this after 45 seconds or so. Driving down the highway car was acting normal. ABS light came on, check engine light came on 1-2 minutes later. One minute after that the car is acting like it is missing spark. Immediately after that the speedo stops registering correct speed, tach goes on/off intermittently, lights on IC flash dimly. 45 seconds or so later the engine is producing no power. I have pulled over at this point, shut car off, try to start, no crank. Stomp test 1231 DME Main Relay/Voltage issue. Lights, radio, clock all working fine. Wanted to check relays, fuses, etc, but position on shoulder prohibits this. Walked the ~1.5 miles to home.

So, DME relay failure, DME failure, fusible link or something I am overlooking? Let me know your experiences/thoughts if any.

[jntar]

Battery could have a bad cell. Alternator could have shorted out. Relay could be bad. Ect...It's in the charging system somewhere. Start with the cheap items (Take battery to autoparts to test for dead cell) then go from there.

1231 - Battery Voltage / DME Main Relay error code can mean that battery voltage is out of range (either too high or too low), or that battery was disconnected. Test charging system and /or battery to find problem cause.

[roguetoaster]

While it is possible that it is the alternator/battery that would surprise me as there isn't even the faintest hint of a crank from the starter (and it's not too old of a starter) and the other electronics work fine, lights (even high beams), etc. Other ideas?

I will start with the simple things as soon as I get it home of course. With the relay being #1 on the list.

[jntar]

While it is possible that it is the alternator/battery that would surprise me as there isn't even the faintest hint of a crank from the starter (and it's not too old of a starter) and the other electronics work fine, lights (even high beams), etc. Other ideas?

I will start with the simple things as soon as I get it home of course. With the relay being #1 on the list.

Your radio and ect can still work, but with a shorted cell in the battery when you attempt to pull amperage with starting it would fall on it's face and not do anything. Give the battery a test, it's the cheapest place to start.

[roguetoaster]

Thoughts on how this would cause the engine to shut down in such a progressive manner at highway speeds?

[Dj Buttchug]

no more spark to ignite fuel. Its in the charging system. cars do weird things when the electrical system isnt working right.

[future rs]

Thoughts on how this would cause the engine to shut down in such a progressive manner at highway speeds?

Certain components require more amperage to operate. The loss of power coupled with the alternator supplying power as well can cause a progressive power loss.

I had a cooling fan rub a hole in the corner of a battery and had a very similar experience. As the battery lost the ability to keep up the alternator was supplying enough to keep things going for a bit until it was too much draw to keep up with.

[roguetoaster]

Update

Initial thoughts were failure of alternator caused battery to discharge, thus no spark, yadda, yadda, yadda.

Changed alternator to working unit from spare car, at the same time changed alternator to engine ground strap as the old one was corroded and casing was damaged. Inspected grounds. Checked voltage on battery, 6.4v with battery ground strap unhooked, .4v with strap connected!?! Makes my more clear headed brother think there is hot ground, makes sense. Pulled all fuses and attempted to hook up a remote battery for a jump, only to be treated to a some very concerning sparks when just touching the second cable to the terminal/connector. Double, triple, and quadruple checked that the cables were not crossed or confused and that ground was solidly in place. Tried touching connections again with battery out of loop, same result. Checked for continuity between rear positive battery cable and front pole mount, all good. Going to inspect fusible link and who knows what else, but quite stumped right now.

Yes, before you ask, the jumping sequence was car positive terminal then car negative battery cable to body unhooked from battery.

[lolcantturn]

try a new dme ?

[kwill22]

I thought if the battery registered higher when disconnected and the voltage dropped dramatically like that when connected it meant the battery is bad.

[roguetoaster]

Solved

Apparently the brushes in the alternator were worn down to nothing/had a random failure, caused low output, drained battery and stopped car. Swapped in the other alternator only to experience some other sort of failure (the sparking, probably due to bad resistor or something of the sort). Took brushes out of that alternator, installed in first (one in the car when it died) alternator, jumped, all was well.

This is omitting the obvious steps of isolating what component was causing the issue, but it's solved so who really cares. A side note, for several days before the car died it felt as if it was low on power, with the alternator fixed it feels back to its peppy self.