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.

rshafferdc · #7 12-31-2005, 05:26 PM

I had a similar problem recently......but, I am mostly likely dealing with much warmer temps......just under 40 degrees. I ended up having 2 problems.

My glow plug relay was bad, even though the glow plug light did come on at the dash. It came on, but for much shorter time period than it should have. The relay looked fine on inspection and it's fuse was fine. When I took it out it to put a "junk yard car's" on, I realized it had oil dripping out of it (just got the car over the summer). Once I had that fixed......immediately I had the dash warning lights stop working, but the dash glow plug light worked fine. Then I replaced the voltage regulator and everything worked the way it should. I too was having the "cranking" issue and my battery didn't seem to stay charged, but the "battery" dash warning light was lighting up so dimmly I couldn't notice it unless it was dark outside.

Just an idea...thought I'd share my experience.

adiaw83 · #8 01-02-2006, 07:34 PM

My autozone didn't have any 0w-40 ro 5w-40. Would 5w-30 be alright or should I find something else. I just got a brand new battery from them at no cost too so I'm pretty excited about that. My voltage regulator should be here by tommorow so I'm gonna hook everything up then and be back on the road. Someone please let me know about the 5w-30 oil though. thanks

whunter · #9 01-02-2006, 08:44 PM

Quote:

Originally Posted by adiaw83

My autozone didn't have any 0w-40 or 5w-40. Would 5w-30 be alright or should I find something else. I just got a brand new battery from them at no cost too so I'm pretty excited about that. My voltage regulator should be here by tomorrow so I'm gonna hook everything up then and be back on the road. Someone please let me know about the 5w-30 oil though. thanks

No, too thin..
You need 0w-40 or 5w-40 synthetic.
The phone book is your friend, any major auto supply, truck stop or oil supply company can get it.
Try Wal-Mart also...

Brian Carlton · #10 01-03-2006, 01:02 AM

For the climate in Washington, DC, you probably can get away with 10W-40. It's much easier to find than the grades Roy listed. Make sure it is a diesel rated oil. It will have a "CH" or a "CI" designation on the container.

adiaw83 · #11 01-03-2006, 11:42 AM

Thanks Brian. So I just put the new battery in my car. I went inside to turn it on and put the key in the glow plug position and nothing happened. The light dimmed so much that it was almost off and the dash lights didnt really come one. I tested the battery and it read 10.6 volts. Don't really know how that happened but I will be going back there tonight

adiaw83 · #12 01-05-2006, 10:53 AM

The car started up very strong this morning after taking all of your advice. It took about a week for me to find and do everything but it is welll worth the effort. I ended up getting a brand new battery, tighterning one of the bolts on the #5 glow plug, putting in a new voltage regulator and changing the oil to mobil one 0w-40. thanks a lot for all of the help and it feels good to be back on the road again.

Brian Carlton · #13 01-05-2006, 04:33 PM

Quote:

Originally Posted by adiaw83

The car started up very strong this morning after taking all of your advice. It took about a week for me to find and do everything but it is welll worth the effort. I ended up getting a brand new battery, tighterning one of the bolts on the #5 glow plug, putting in a new voltage regulator and changing the oil to mobil one 0w-40. thanks a lot for all of the help and it feels good to be back on the road again.

Excellent news.

Help is what we do here.

whunter · #14 01-05-2006, 05:53 PM

Quote:

Originally Posted by adiaw83

The car started up very strong this morning after taking all of your advice. It took about a week for me to find and do everything but it is welll worth the effort. I ended up getting a brand new battery, tighterning one of the bolts on the #5 glow plug, putting in a new voltage regulator and changing the oil to mobil one 0w-40. thanks a lot for all of the help and it feels good to be back on the road again.

That is great news.