Conditions: Dry and temperature in the 80°s and low 90°s

Over the past 6 weeks I will go to start my 300SD and one of three things will happen:

It will start

It will slowly turn over then start or not start

It will not even turn over. In fact the battery will be completely drained.

This happens probably one out every 8-10 attempts to start it.
If it fails to turn over, I have been able to go out to it a couple of hours later and get it to slowly turn over and start.
The car has a six month old battery that has been examined and will hold a charge.
The connection to the starter motor is tight.
The alternator has been checked.
The Glow Plug Relay has been replaced (thought the power might be draining through it).

Could the starter motor be connected to this phenomenon?

Thank you for your interest and any help

__________________
Anders

1995 E300
2015 VW TDI Sportwagen 15K
1977 240D (197K)
2002 Subaru Legacy L Wagon (115k) (Wife's)
Gone but not forgotten:
2005 Buick LeSabre
1998 C230
1984 300D
1983 240D
1981 300SD
1974 240D
1974 Fiat 124 Spider
1968 Triumph TR250

andersbenz,

I would first look for a bad connection on the battery terminals or any of the connections of the high current cables between the battery and the solonoid or ground.

One easy way to do this is when it won't start, feel all the connections for a hot spot. If you find a hot spot, this is a point of high resistance and could be your problem. You could also check the terminals on the solonoid and starter the same way.

P E H

PS: Be careful you don't burn your fingers. Don't grab anything too tightly at first.

If this is true, you can't blame the starter motor, or any positive or ground connections to the starter motor.

Are you sure that the battery is "completely drained". It might be possible that the battery is fully charged and the starter is behaving intermittently.

Additionally, it might be possible that the battery is not fully charged.

If true, then the alternator is likely the culprit. I had the SD's alternator acting intermittently for a couple of months before the symptoms became brutally obvious.

If you can, when the problem surfaces, take the battery out of the vehicle and see if you can get it tested. If it is fully charged, the problem is the starter, or one of the ground connections. If it is discharged, the problem is likely to be the alternator.

Same here I had a voltage regulater that was bad adn being intermittant about once a month....always worled fien when I checked it...Until I smoked my steereo, the Tachometer and half the lights in the car 2.5 hours from home...found it putting out about 18 volts running.......battery died as a result too, it was less than a year old.

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

Thanks Brian, P.E.Haiges and BHD.

Replaced alternator with rebuilt Bosch unit. Problem reappeared. Battery pulled and check. Battery is o.k.

What else could act intermittently? Could the starter motor drain the battery?

Thanks,

__________________
Anders

1995 E300
2015 VW TDI Sportwagen 15K
1977 240D (197K)
2002 Subaru Legacy L Wagon (115k) (Wife's)
Gone but not forgotten:
2005 Buick LeSabre
1998 C230
1984 300D
1983 240D
1981 300SD
1974 240D
1974 Fiat 124 Spider
1968 Triumph TR250

When you pulled the battery, was it fully charged, or did it need to be charged?

Now, you need to be sure you have a fully charged battery.

The problem is in the starter, or the cables, if the battery is fully charged.

The problem is a voltage leak somewhere, if the battery is not fully charged.

To test for a voltage leak, shut off everything in the vehicle and close all the doors. Take the negative cable off the battery and connect an ammeter in series between the terminal post and the cable end. See what the ammeter reads. Anything above 60 mA is too much. Start pulling fuses, one at a time, until the draw drops below 60mA. The clock and the radio will draw something around 40-60 mA. You are looking for a bigger voltage leak (above 100mA).

It would be highly unlikely that the voltage leak is through the starter, but, I suppose that it is not impossible. You would need to disconnect the starter lead to confirm this, if you get a high mA reading on the aforementioned test, and none of the fuses will lower the reading.

Are your cables clean and tight? A corroded or loose ground can do strange things...Make sure you check both ends....A solenoid could in theory do that if sufficient carbon tracking has developed....but i have only seen that happen on a Harley-Davidson Prestolite Solenoid. But to avoid duplication what Brian said goes too.

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

Brian,

Just to keep the terminology correct its a current leak not a voltage leak.

P E H

Thanks PEH............always looking out for me.

Strange electrical problem solved (I think).

After two months of this problem, my independent mechanic suggested replacing the battery even though it was purchased in December. Problem solved. He thinks a couple of the cells in the battery had an intermittent short, which would drain the battery on an erratic basis.

Well it has been a week since I replaced the battery and the car has been running fine. It has been driven in stop and go traffic and as well as on the local highways with no starting problems.

What a relief.

I am enjoying driving the 300SD again.

Thanks again forum members for your input.

__________________
Anders

1995 E300
2015 VW TDI Sportwagen 15K
1977 240D (197K)
2002 Subaru Legacy L Wagon (115k) (Wife's)
Gone but not forgotten:
2005 Buick LeSabre
1998 C230
1984 300D
1983 240D
1981 300SD
1974 240D
1974 Fiat 124 Spider
1968 Triumph TR250

That's certainly a new one. This battery checked out properly on a load test?

Be very interesting if the battery can pass a load test and have an internal short. But, seems quite possible. With all of the defective merchandise today, nothing is surprising.

Glad it fixed the problem.