Hey gang, I've got a 79 300TD with a starting problem.

Here's the scenario:
- brand new MB battery
- get in the car and the dome light is on
- turn the key and get the usual dash lights for a hot sec and then gone in the blink of an eye
- no crank no nothing and then there's no power anywhere - even the dome light and the second try there are no dash lights at all
- check the battery and it's at 12.9 volts after all of this
- same effect when jumping the car

- if I charge the battery then it all starts over again with the dome light and brief dash lights

Any thoughts? Ground issue? Just need some ideas where to even begin to start troubleshooting this.

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Nice looking wagon.

You have a bad connection somewhere. I'd inspect the cables going to the battery real close.

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Jim

You have a great looking car! Along the same line as above, check the negative/ground cable and connections from the engine to the chassis. It’s on the underside of the engine.

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Marshall Welch
Seattle, WA
1982 300D-T

And X3... closely inspect both ends of both battery cables, the braided ground strap to the bell housing and the wires/plug at the back of the alternator.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

As the others said remove and clean down to the bare metal all cable contacts areas.

Remove the fuses one by one and check them and their tips and the contact inside of the fuse box. Fuses with plastic bodies can warp and cause poor contact even though the metal strip seems OK. I had a fuse that looked good till I pulled it and found the tip of it was corroded and gone.

You can hook up a remote starter switch or use a jumper wire to see if the starter will crank. When the starter is cranking it turns the glow plugs on during cranking. It can eventually start like that but that does not mean for sure you will be charging the battery while the engine is running.

However, my gut feeling is you are having an ignition switch and or steering collum lock issue and that is between the lock tumbler and the ignition switch.

I had parts inside of my steering collum lock break and there was no start. The new steering collum lock assembly came with a new initiation switch and a new vacuum switch. I don't know if they are available anymore.

When I inspected the old ignition switch, I found the contact point on one of the contact arms was burned down to the meatal of the arm itself.

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84 300D, 82 Volvo 244Gl Diesel

As the others said remove and clean down to the bare metal all cable contacts areas.

Remove the fuses one by one and check them and their tips and the contact inside of the fuse box. Fuses with plastic bodies can warp and cause poor contact even though the metal strip seems OK. I had a fuse that looked good till I pulled it and found the tip of it was corroded and gone.

You can hook up a remote starter switch or use a jumper wire to see if the starter will crank. When the starter is cranking it turns the glow plugs on during cranking. It can eventually start like that but that does not mean for sure you will be charging the battery while the engine is running.

However, my gut feeling is you are having an ignition switch and or steering collum lock issue and that is between the lock tumbler and the ignition switch.

I had parts inside of my steering collum lock break and there was no start. The new steering collum lock assembly came with a new initiation switch and a new vacuum switch. I don't know if they are available anymore.

When I inspected the old ignition switch, I found the contact point on one of the contact arms was burned down to the meatal of the arm itself.

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84 300D, 82 Volvo 244Gl Diesel

I know of no specific way to determine if it is the ignition switch itself or somehow the power going to the ignition switch is the issue. The fuse chart should say which fuse is the fuses used by the ignition.

If you remove your alternator electrical connector there is 3 slots. The 2 large slots are connected direct to the battery and have battery voltage all of the time. The smaller slot is eventually connected to the ignition switch and when the switch is off there is no batter voltage and when the ignition switch is on there is just slimly less than battery voltage.

So that is easy to access on most W123s to see if that part of the ignition switch is working. Note that when you first turn the key on you need to see a working charging light. If that bulb is burned out, you also won't get voltage to the small slot.

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84 300D, 82 Volvo 244Gl Diesel

I know of no specific way to determine if it is the ignition switch itself or somehow the power going to the ignition switch is the issue. The fuse chart should say which fuse is the fuses used by the ignition.

If you remove your alternator electrical connector there is 3 slots. The 2 large slots are connected direct to the battery and have battery voltage all of the time. The smaller slot is eventually connected to the ignition switch and when the switch is off there is no batter voltage and when the ignition switch is on there is just slimly less than battery voltage.

So that is easy to access on most W123s to see if that part of the ignition switch is working. Note that when you first turn the key on you need to see a working charging light. If that bulb is burned out, you also won't get voltage to the small slot.


See post 2 for a pic of the wire terminal black on the fender well about 8 inches from the battery. If you have that you can test for battery voltage and also use a remote starter switch or a jumper wire to crank the starter. The 2 rear wire terminals have battery voltage (like your cables those where they make contact may need to be cleaned). The front terminal has a white wire that goes to the starter solenoid and a lavender/purple wire that goes to the glow plugs relay.

So, for jumpering you just go from either of the rear terminals to the front one.

For testing put your voltmeter or test light on the front terminal and the other end to a good ground and when the ignition key is turned to cranking the starter you should get electricity there.

No voltage during that test can be the ignition switch or the neutral safety switch.

What gauge of wire to use to safely manually trigger the starter or glow plugs?

In post number 1 you see a picture of where the shaft inside that turns the ignition switch inside of my steering collum lock broke off and would not turn the ignition switch.
Steering Colum Lock (Ignition Lock Housing) causes Ignition Switch Failure

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84 300D, 82 Volvo 244Gl Diesel

Thanks guys, got her running last night. Turns out it was an intermittent connection in the positive battery cable. It was well connected to the battery but wiggling the wire caused the connection to go in and out. So, diagnosed and now to replace the cable.