1985 318i Died While Driving, Possible Charging Or Electrical Issue?

[BadDays]

Folks, I'm coming on here to ask if anyone else has experienced this issue before.

Recently as I was driving to get parts for my passenger door, My car lost all power and I had to pull over. After Popping the hood and checking to see what went wrong, I attempted to use this forum from previous posts to diagnose what could be causing my car to die right after it started up but as I went through previous posts and even Reddit. I have this: The car did have enough spark and fuel/air to get the engine running about 3 days ago, Though when I did put on the radio and heat together, the radio cuts out.

As of today, The car has no electrical power and the battery is only 3 months old, I attempted to jump start my car with a friend's help and it still died after one startup. However Whenever the negative terminal is connected, The Fuel Pump automatically makes a noise indicating the car has full power to all systems but there was nothing, Could it either be a charging system issue or some parasitic draw is causing the electrical system to malfunction? Any help is appreciated.

[roguetoaster]

What is the battery voltage as it sits, and when the engine is actually running? You'll need a voltmeter of most any type.

Normally, there will be some odd lights, strange engine behavior when the batt voltage drops too low when driving, then the car will cut out.

Sometimes there will be strange things when the battery voltage is too low to start the car, but not totally dead.

[BadDays]

Going to check voltage on the battery and alternator tomorrow, However it seems like every time the key is inserted and turned to the ignition, The signal to the fuel pump is less and less. Will definitely need to go through charging system and see what the hell's going on with it.

[BadDays]

Alright so after testing voltage to the battery and alternator, the alternator is charging and battery was drained because of the jump start. However as I pulled the fuel pump relay. I come to find out that this little guy is absolutely fucked no doubt

Someone in the past decided it was a good idea to open this relay and "attempt" to fix it. It's a miracle this relay lasted as long as it did.. I made sure to check the P/N and it matched with the one I bought today, should be here in a few days. Fuel pumps were replaced about 4 months ago before I got the car.

[roguetoaster]

Fine about the relay, but how could a battery get drained by a jump?

[reelizmpro]

Early 318i's have alternator bushings that can wear down causing the belt to slip so check those and the belt tension. The alternator bracket adjuster teeth are known to fail. It also has an alternator ground wire so check to make sure it's not fried, frayed or broken. Remove, inspect it and clean the mounting points. Check all the engine grounds while you're at it.

[BadDays]

Fine about the relay, but how could a battery get drained by a jump?

I assume since the car wasn't started in two days, the battery slowly drained itself, Honestly I'm still scratching my head but got it recharged, As for the alternator, I had to take it out to get it tested at a local shop, The alternator is working properly and I made sure to re tighten the belt properly after putting the alternator back in. Cleaned up the ground strap and then for shits and giggles, The D+ wire broke it's connector as I was putting it back on so I'm off to solder in a new connector tomorrow -_-
Also Jumped Pins 30 and 87 and we have voltage to be sure.

In the meantime as I wait for this relay to come, I'll continue to read my Bentley manual and troubleshoot this problem as it states there's three possibilities for why this could be happening.

[BadDays]

Came back here to update what's going on, Yesterday I made sure to retest 30 and 87 along with 15 on continuity. We have 7 volts going to 30 and 87 but shouldn't this be 12 volts? 1.4 OHMS on 15 and retested again with a drop to 1.2, I dug deeper by jumping the pins with a 14 gauge wire with two connectors so when I turned the key and tried to hear the pump, Nothing. I pulled the backseat and checked the internal fuel pump with the multimeter, The Green and Violet plug (according to my ETM on this model) has no voltage with key turned to ignition. We found the problem.

With 7 volts to the relay and no voltage to the pump, I can believe that I need to trace the wiring back to the fusebox and investigate this problem. However there is good news, I will be upgrading the fuel pump and it's wiring so that way there's only one pump and therefore if it happens again? I can immediately diagnose what can go wrong. I'd say this is concluded for now.

[packratbimmer]

Good move on upgrading to a single pump system!

[BadDays]

Thank you! Okay I'm closing this thread by concluding that the ECU was the culprit.

I had to compare my situation to a video about a honda accord doing the same shit to realize what was happening to me in the first place.

I checked the ecu and sure enough it was fried, Hopefully I can give some advice here:


Check your ECU if your car is cutting out electrically. If you notice the car stalls after starting and you ruled out all possible issues execpt for the ECU. It doesn't hurt to check it. Thanks again to everyone for the assistance!