87 300TDT No start no spin

[robertb1958]

All, I scored an 87 diesel wagon in exceptional physical condition but with a bad "14" head, then scored a donor sedan with a replacement 22 head and 100K less miles.

Been driving the wagon with the swapped in motor for a couple of weeks. After a few tweaks, it has been running great, starting at the touch of the key when warm, and with a little glow when cold, no problems whatsoever.

Then, this AM, I turned the key after giving it a good glow...

NOTHING. No sound, click, weak groan spin, nothing. Dash lights are on, all seems normal but no motor spin.

Thought, well the battery had been weak and something drained it. I did not have much time or tools, checked with my Fluke, only 11.9V from the battery. I got a Lyft ride to the office (its close) where I have other cars. Drove the W210 back home, put a charger on the W124 battery.

Later this afternoon my smart charger indicated 100%. Still nothing. Swapped batteries, and again, nothing.

I guess there is a starter solenoid somewhere, my best guess at this moment unless there is a relay somewhere that could be the culprit. Could be the key switch, also, I suppose.

Would appreciate ideas and a link to a wiring diagram for this model (1987 300TDT OM603) Thanks!

[Diseasel300]

Start with the transmission. Try starting it in Neutral. If it starts, you likely have worn (or missing) shifter bushings (the 2 under the car) or a failed/failing neutral safety switch.

[robertb1958]

Thanks, pretty sure I tried it in neutral, will try again.

[Mxfrank]

It's not too hard to pull the connector off the lock out switch and short the ignition side (the switch does double duty as the reverse light switch, so you have to short the right pins). It's mounted to the left side of the transmission.

[treetops]

Everything properly grounded?

[Junkman]

Is there a junction block on the passenger side of the engine compartment on a 123 that can be used to bypass all of the lockout switches?

Is the small wire to the solenoid getting current with the trans in park and the key to start position? That would confirm key switch and trans lockout (ie NSS) switch. Contacts in solenoid could be bad.

You can measure voltage drop at all of the various points in the starting system. ie battery post to cable terminal to connection at solenoid and comparable on the negative battery side.

[robertb1958]

Back at home, I wiggled the shift lever all around while holding the key in start position. I hit a sweet spot, she fired right up.

So, either a flakey NSS and/or shifter bushings.

Thanks for the help!

[jay_bob]

Very common problem on these cars. Search around for the tips on how to replace the bushings, they are too stiff to press in with your fingers unassisted

New bushings make a huge difference in the feel of the gear shift. If your handle flops around like a dead fish instead of snapping into position, I would try bushings first.

[tyl604]

Yes, bushings. Worked like a charm on my '81 SD. Be sure to soak them in boiling water before trying to install; helps a lot to soften them up.