300D won't start.....Issues with Starter/Solenoid/Wiring/Battery

[stellwagen]

I've got an issue I'm trying to figure out on my '79 300D.

Yesterday, she was driving totally normal. Drove through some rain, puddles; parked on a slight downhill (mentioning these in case they matter).

This morning, went to start and the engine hardly turned over. Turning the ignition, I can keep the engine turning but at a very slow rpm (like when battery is low).

Thinking the battery might be the issue, I tried to jump it but that didn't make a difference. Battery sits at ~12.25v - low but not terrible (jump it was at about 12.7). Cleaned battery connects and the ground next to the battery. Also whacked the starter with a hammer a bit. Cables from battery to solenoid seem to test well (voltage drops ~.1v)

The one thing I've found, is that when cranking, the battery reads ~3-4v which seems really low. I watched one video where the guy said it shouldn't fall below 10v. Does this conclude wiring? Or could it be battery?

Any tests I can run? It was hard to see in there real well. Is there a trigger wire in there I can test? This is odd because this issue came with no warning.

[cooljjay]

How old is the battery? Does your battery light on the instrument panel, light when the car is started? You can take the battery in to any autozoo and have it checked/tested for free...

Jumping these cars, require thick cables at least 2 gauge...

[uberwasser]

First suspect is the battery being bad. Is there any way you can remove it and take it to an auto parts store for a test?

If the battery tests good and was simply drained, next suspect may be the voltage regulator. I've personally experienced a case recently where one failed suddenly and without warning.

I'd say it's far less common for a starter or a wiring issue to crop up so suddenly.

[stellwagen]

Originally Posted by cooljjay

How old is the battery? Does your battery light on the instrument panel, light when the car is started? You can take the battery in to any autozoo and have it checked/tested for free...

Jumping these cars, require thick cables at least 2 gauge...

Unsure of the age of the battery. Car is ~4 months old to me. Duralast.

I brought it to the auto store and the guy said it was good, but charged at 52% and I should replace an alternator. I think he's jumping to conclusions. Though, it is possible. The alt belt has been squeaking lately, perhaps it wasn't charging enough and the recent rain storm made is slip too much?

I tried jumping with my brothers' Volvo 240 to no avail. Can these 300D's be jumped by cars with smaller batteries using standard 10 gauge jumper cables?

[stellwagen]

Originally Posted by uberwasser

First suspect is the battery being bad. Is there any way you can remove it and take it to an auto parts store for a test?

If the battery tests good and was simply drained, next suspect may be the voltage regulator. I've personally experienced a case recently where one failed suddenly and without warning.

I'd say it's far less common for a starter or a wiring issue to crop up so suddenly.

Battery tests 'good' but low charge at the auto store, though who knows.

Do you just mean the regulator on the back of the alternator?

[cooljjay]

10 gauge jumper cables won't do anything, you need the thick guys....I have jumped smaller car batteries with my car but never the other way around so can't say that...

Well if he says its good, look on the battery for a month/year sticker....

If the belt was slipping, that would be the issue. First you need to make sure that battery is full and it should start...

Another thing, I would check out. Is your chassis to engine ground cable, it is on the drivers side right under the car, running the the bell housing...its possible something happened to it..

The battery cables on these cars, are very thin and are known to corroded under the sheathing. I would take a really good look at them and then add to your list to get 2 gauge cables in the future.

[barry12345]

All that is wrong is you have a loose or bad alternator belt. Anytime you hear the belt scream at you. Call it squeeling if you want there is a problem.

Usually this will occur just after you start the car and pull away. The alternator is demanding high output to restore the lost current from starting. So the belt slips seriously causing the noise. That belt will continue slipping but there will be no noise as the load lessens.

Twelve point two five volts is for all practical purposes a pretty discharged battery. Typical of an alternator belt with low traction. Rubbing the vee portion of the belt with common household bar soap will give or restore the belt traction for a day usually. Good to know on a long road trip if you have the problem. Usually will not interupt the trip then.

[Diesel911]

There is a Chassis to Bell Housing Ground strap under the car about where your Feet are.

I got up one morning started the Volvo Diesel. When somewhere. Care started normally when I left there.
I made a stop to get something to Eat. Got in the Car and turned the Key and nothing at all happened and this is on a Manual Transmission so no Neutral Safety Switch.

I had a Voltmeter and I had 12.5 Volts.
I got a piece of Wire to try to jump the Starter Solenoid and I found out the Spark was tiny. The showed that I had Voltage verified by the Meter and lack of amperage verified by the weak spark.
I walked a cross the street and bought a new Battery and installed it and was on My way.

My Battery evidently damaged inside.

[barry12345]

I too have experienced this as well. Battery seems fine and perhaps later it the day was totally dead. Was internal battery problems.

Attempting to recharge those batteries did nothing. You have to do this just to make sure some short did not erupt in the car and discharged the battery.

[jay_bob]

Automobile batteries are composed of six two volt cells in series inside the case. If one of the cells fails, its internal resistance goes up. In this condition, low current devices, like instrument lamps, your radio, etc. will work normally. But when you hit the starter, the resistance of the bad cell prevents a large current from flowing.

Kind of like when you have a minor accident or lane closure on the highway. At night or time of low traffic everyone gets by. But at rush hour everyone gets held up.

I would have the battery load tested at the parts store.

[Silber Adler]

When I see a sudden loss of battery power. I think of a bad battery cable or ground first. Give your battery a full charge before testing it. If 52% is right then it may be a dud.

The voltage 'while running' was only 12v on my 85 300d. If left for a few days it wouldn't start. The regulator on the alternator is at the bottom of the engine compartment. I got a new regulator at peach parts for less than $20 and changed it from under the car. Now am getting 14 volts while running. Battery stays charged. It only took a small wrench or nut driver to change.

[cfh]

I recommend disconnecting the battery cables when charging - I recently ruined my alternator charging the battery (blew a diode or diodes so battery light stays on even when car is off; alternator drains the battery when the car is off and does not seem to charge the car when it's running). Just got a new (used) high amp alternator and swapping that in is my chore for this morning. Would have been much less hassle to just disconnect the cables before charging.

[barry12345]

Originally Posted by cfh

I recommend disconnecting the battery cables when charging - I recently ruined my alternator charging the battery (blew a diode or diodes so battery light stays on even when car is off; alternator drains the battery when the car is off and does not seem to charge the car when it's running). Just got a new (used) high amp alternator and swapping that in is my chore for this morning. Would have been much less hassle to just disconnect the cables before charging.

If you feel that way disconnection of one battery cable should be the same as removal of both cables electrically. The car is isolated from the charger to the battery either way then.