1983 300 SD Charging system problems - PeachParts Mercedes-Benz Forum

adiaw83 · #1 12-24-2005, 12:57 PM

My 1983 300sd is struggling right now. I have already changed the glow plugs this winter. The car sat for most of the month of december at my school. I tried to start it one day and the starter just clicked. This has happened before so I just did what I normally did and took the battery to autozone where they fully charged it for me. I went back to the car, hooked the battery up and jumped the car from a 300SL battery. The car started very strong on the first attempt. Hardly even cranked. I drove the car around a bit that evening. I started it up by itself about 5-7 times but this was not on a cold engine so it started up fine. I put the car in the driveway around 1am this morning and I went out to start it around 1130am and it cranked but would not start. I tried jumping it from the 300SL again and it cranked but would not turnover. I'm pretty sure theres something wrong with the alternator hopefuly just the voltage regulator. I'm going to get my hands on a voltemeter and check the voltage at the battery with the car on and off. Does anyone have any ideas on what the problem could be? thanks

Brian Carlton · #2 12-24-2005, 01:53 PM

A voltmeter would be the first line of attack.

Connect it to the battery with the engine not running. Read the voltage. If it's below 12V, get the battery charged before proceeding.

Start the engine.

Rev it to 2000 rpm and keep it there after it has warmed for two minutes.

Read the voltmeter again. If it reads less than 13.4 volts, shut off the engine and replace the regulator. Make the check again to confirm 13.4 volts or greater.

If it reads 13.4 volts, or more, then the regulator/alternator is not the problem.

Report back and we'll continue.

adiaw83 · #3 12-24-2005, 03:04 PM

thats what I figured I'll try to get to autozone today and pick up a voltmeter

Brian Carlton · #4 12-24-2005, 03:27 PM

Quote:

Originally Posted by adiaw83

thats what I figured I'll try to get to autozone today and pick up a voltmeter

Radio Shack has a tiny one, about the size of a pack of cigarettes. Has been with me for 20 years and never failed. I have a larger meter with multiple ranges for resistance for more complicated tasks. But, the small one is ideal for what you are looking to do.

The auto parts stores will have what you want, but for more money.

adiaw83 · #5 12-30-2005, 11:52 AM

I just got the car started. It took a lot more trouble than normal this time. The starter had the car basically running but it took the engine a while to turn over on its own. I tested the voltage with the car at 2000rpm and it was at around 13.7 so I guess its not the alternator. I'll test the resistance on the glow plugs to see if thats the problem however I already changed GPs 1,2 and 4 before i tested them and they didn't have any wet oil on them.

adiaw83 · #6 12-30-2005, 03:38 PM

I tested the the glow plugs and they all read .6ohm. I just changed the oil to mobil 1 15-50 so hopefully this will help with the starting. I'm not sure what else I should diagnose at this point. Any input is appreciated.

TheDon · #7 12-30-2005, 03:43 PM

have you changed the fuel filters? maybe something is clogged in that system and your not getting enough fuel to turn over

Pete Burton · #8 12-30-2005, 04:06 PM

Are you getting proper current flow to those plugs? Take the 80 Amp glowplug fuse COMPLETELY OUT and look at it carefully. I had one crack once - enough to let a little current through, but not nearly enough.

adiaw83 · #9 12-30-2005, 09:15 PM

I'll inspect the fuse more carefully. I recently placed the main and secondary fuel filters as well. There is a bit of fuel on top of the assembly for the main filter so I think i might need to tighten something.

Brian Carlton · #10 12-30-2005, 09:44 PM

Please correct me if I am mistaken:

The only time that the engine started immediately when cold was with a fully charged battery and with a jump start from another vehicle?

Every other time it was started, cold, it gave some trouble????

If this is true, then I have the following additional questions:

1) How old is the battery?

2) Has the battery been tested for CCA output?

The symptoms, if I've read them correctly, appear to be a lack of cold cranking amps. It's more difficult to start a diesel when it's cold, as you certainly know.

whunter · #11 12-30-2005, 09:58 PM

Quote:

Originally Posted by adiaw83

I tested the the glow plugs and they all read .6ohm. I just changed the oil to Mobil 1 15-50 so hopefully this will help with the starting. I'm not sure what else I should diagnose at this point. Any input is appreciated.

It should be 0W40 or 5W40 synthetic at this season in DC...

15W50 is thick as molasses.

Meta6981 · #12 12-30-2005, 11:24 PM

I had a little bit of a similar problem. Occasionally my car would do one or wur's then nothing. It was intermitent and was solved with a new battery i got at sears auto center for like 130$.

kmaysob · #13 12-31-2005, 04:45 AM

you dont have that stupid battery terminal grease on the posts do you? that can cause alot of problems. belive me i had the same problem.

adiaw83 · #14 12-31-2005, 02:38 PM

I dont have ant terminal grease on the battery. I think the battery is the culprit. This morning I tried to start the car and it turned really hard for about 4 seconds then all of a sudden started cranking really slow like the battery had a very limited charge. Thanks for that tip about the oil. I'm still on dino now but I had 15w-50 in there last winter. Guess I should understand my oil wwights better.

whunter · #15 12-31-2005, 05:06 PM

Quote:

Originally Posted by adiaw83

I dont have ant terminal grease on the battery.

ant terminal grease!!!

:CRACKING UP:

I needed a good laugh.