[Mexican_kidd]

alright i got a 1978 240d a few weeks ago. was running fine and all of a sudden it wont crank. i was driving it the night before and the aftermarket radio started freaking out and then shut off. later the car would not crank, had to roll start it. had the car check on an they charged the battery cranked first try after drive it back home turn it off and then later turn it back on and it wont crank its like if the batter was dead again. had to jump start it again and boom cranked but the radio was turning on and off now it wont turn on and neither the car. HELP HELP anybody know what could be wrong?

 

[techno]

My first guess would be alternator issues from what you described. The first thing I would check would be the voltage regulator on the back of the alternator. If that is in working condition you may need to get a test on you system.

How old is your battery?

 

[bricktron]

battery and alternator/VR are both suspect, check for blown fuses under the hard-to-remove fuse box cover. buena suerte, y si sigues con este carro conoceras como es que anda!

 

[uberwasser]

The battery is not getting charged by the alternator. Get it tested, next.

 

[codepony]

Ius the battery the right size? Should be a huge-ass truck battery, at least 800 CCA.

Also, yeah, alternator. You can rebuild it or replace it. Check the regulator first though, it's usually the problem and much cheaper then an alternator.

 

[300Dman]

If you continue to drive it and have not found the problem I would disconnect the Negative Battery Cable when I park it to prevent any further drain.

When you first turn on the Igniton Key all of the Warning Lignts inclusing the Charging Light shouuld light up. If the Charging Light does not light up you should check the Bulbe to see if it is burnt as you need to have the bulb in the Circuit or your Alternator will not charge correctly.

Disconnect the Electrical Connector at the Alternator and you will see it has 3 slots. The 2 large slots always have Battery Voltage.
Ths single smaller slot only had Voltage when your Turn the Key on. That is the one that goes to the Ignition Switch and the Battery Charging Light on the Instrument Cluster.

 

[Mexican_kidd]

thanks you guys! HUGE help. well since my motor is litterally covered in oil since one of my hoses was busted finally replaced it today. any problem if i degrease the motor while its on? or does it have to be off? after that i shall go get the battery test and also the alternator and go from there.

 

[uberwasser]

De-grease the motor while the alternator is attached, you mean? Not a bid deal, just don't spray the alternator when rinsing it. Consider covering it with a plastic bag to insure it doesn't have issues.

 

[Mexican_kidd]

what i mean is would i have to have the car turned on or off?

 

[uberwasser]

You want the engine to be off, and COLD, when you do the de-greasing. A hot engine can cause the de-greaser to burn or react funny, and if you rinse a hot engine with cold water you can crack hot metal parts.

 

[carnut62]

This era of diesels had a tendency to develop loose alternator belts which would cause the battery to discharge especially at night with the lights on. First thing to check is belt tightness. Try to rotate the alternator pulley by hand (ENGINE OFF!) If you can rotate it, the belt's too loose or already glazed and needs replaced. I've seen many alternator adjuster brackets damaged by inexperienced mechanics and if damaged you are unable to get a proper tension on the belt.

 

[Gregs300CD]

Just remember that in order to tighten belts, you need to:

1) Loosen the bolts securing the part
2) Turn adjusting screw to achieve proper tension
3) Tighten part bolts again

You can't just attack the adjusting screw.

 

[carnut62]

I agree!