my new 77 240D won't go :(
 

Hi,
just picked up a '77 240D that the PO wanted off his driveway quick! so.. i got what seems to be a pretty good condition car for $500! (PO had service records for the last 3 years putting over 4K of work into the car, nothing major, just lots of little maintenance thingies)...
he said the car wouldnt start, but would with a jump.. he thought it was a battery or wiring problem,,, so i went over there with my van, and after charging it awhile with jumper cables, it started to crank. after a bit more charging, it turned over and we drove it home. while driving, the car had no electrical- no lights, blinkers, radio, etc.
got home, parked in driveway and turned it off.. i had the battery tested and charged, tested good.
tried to start,- the car has electrical, lights, blinkers, clock ticks, etc at key pos II.. but when turning the key all the way, no cranking, nothing.
tried a brand new battery fro-m my other 240D, same thing.
hooked it up to my van with jumpers, same deal, accessories work, but no cranking...
i checked fuses all are good.
any ideas what might be happening? why it started the first time with a jump but had no accessories, now i have them, but no cranking..!!

Check for loose grounds or wiring of any kind in the start/charge system, and put a real stern, scrupulous look on that alternator.

also have a real good look at your fuses, Take each and everyone out (make sure you mark them if there's no fuse guide) and Clean them. just because they are there dosnt mean they are good, or not filthy and they are not making a good contact

Answer
 

Two issues are common:

* A bad ground on the cable from your passenger bell housing to the body.

* A bad/broken Neutral Safety Switch http://www.peachparts.com/shopforum/showthread.php?p=646647





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I'm going to hypothesize that because of the accessory on/off oddity that the problem is in the ignition switch. Try jumping terminals 1 and 3 in the junction box on top of the inner fender in front of the battery. If the starter works when you do that, the problem isn't the ground and is most likely in the ignition switch, although I can't rule out some funky alternator problem somehow.

By the way, no 240d is ever going to get out of anyone's driveway 'quick'.;)

Like others stated, make sure all your body grounds are good, there is one on the battery and from the trans bell housing to the chassis. And that the hot wire connections are tight. I had some odd issues once and it turned out to the a loose cable on the starter. Also make sure the car is in park or neutral when you start. These cars have a neutral safety switch that prevents the car from starting unless the car is in park or neutral.

thanks guys!
so here's what i found... possibly a neutral safety switch... or something thereabouts- i pushed the car forward in neutral and then put it back in park- and it cranked! so it must have thought it wasnt in park before. not sure if i really needed to roll the car or if just moving the shifter back n forth a couple times would've done the trick. i'll wait and see in the future if i run into this again, to know if i need to investigate further....

the car started up since i had a recharged battery in there- but when running, I tested voltage at the battery terminals and i'm getting only 11.49V - drove it around the block a few times.. then parked over night. this morning i tested the battery when not running and got 11.95V.
does this sound like a bad alternator? where its not charging (enough) to keep a full charge when running? could it be anything else- are there any other things i should test before pulling out the alternator?

The battery could be draining...Charge it back up, hook it up to the car and let it sit overnight. Check the voltage. Or...
Cranking the engine used up that much juice and the alternator is not charging it. You should have 14+ volts when the engine is running.

Also remember that the engine does not need the battery to run...only to start and run lights, etc.

Definitely a problem with the alternator or the wiring to the alternator. Could be an easy fix with the voltage regulator. Here's a link to it

http://dieselgiant.com/mercedesvoltageregulatorinstall.htm

I did leave the battery hooked up for a few days without starting the car after it was charged and it tested over 12 volts each morning, so I don't think the battery is draining or being drained.
I followed the dieselgiant tutorial on checking the voltage regulator - and looks like mine is toast! In the tutorial his has 2 long carbon shafts, one of mine is only half as long as the other, so I think pretty worn down. Hopefully that's all it is!! I'm gonna swap in the regulator from my 81 240 when my GF gets home from work (it looks like they use the same regulator...) and see what sorts of voltage I get when it's running.
I'll post results later tonite.
See attached photo for the worn regulator!

upon further investigation of the removed voltage regulator-- i noticed that the 3 little wires that should be soldered to the metal fins, weren't even connected anymore!! "now there's your problem" ;)
i'm no master mechanic, but seems they probably should be..... i could prob solder them back, but the carbon posts seems so worn, that i might as well replace it just to be sure. I swapped one from my 81 240D and i was getting 12.95 V at the battery when running rather than the 11.4 i was with the bad regulator.
i am suspicious of the battery not being up to par, it was totally dead when i got the car, and looks pretty old..>! i didnt let the car run for that long, but maybe the faulty battery it why i am only getting 12.9 V rather than 13+ ? i'm gonna swap batteries with my 81 and see if with the 'good' battery and regulator I get proper charging voltage.. which should be 13+ right?

13.5 - 14.5 is acceptable.





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