Finally my day off. I checked by the neutral safety switch (nss) and noticed the shift bushing was worn off. I changed it then tried and the car started right up (ONCE). then a click a few times ,then nothing. I put a new NSS on cleaned all connections and NOTHING? my tester showed continuity on all but one wire, the 2nd from top. I then disconnected the wires from the starter and cleaned the good. NOTHING. Someone suggested the ignition switch. I have a couple of tumblers and an entire ignition assembly. which do you think could be the culprit if it could be that. Any other ideas ya'll

Try jumping the posts on the starter. If it functions, it points towards a problem elsewhere, either in the wiring or the ignition switch.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Do you mean the large wires that connect to the starter with a 17mm bolt to the small wire that connects to a small screw. While i had all wires disconnected to clean them and the + terminal wire disconnected, those 2 wires were touching each other and the + terminal moved and touched the + post on the battery. I got a clicking sound out of my glow plug relay. That wouldn't indicate a glow plug relay problem would it.

Do what Phil said in an earlier post. I have had the same problem with an 81 300d. Bad engine ground. It can also be checked using an ohm meter between the engine and battery ground. The reading should be low-several ohms. If not you have a bad ground to the block/starter.

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81 300D Turbo 190K sold
83 300sd 319K best $500 I ever spent-daily driverw/ 2 tank WVO set up

I definitely am going to try Phil's suggestion. Is the ground the small wire attached to the starter by a small screw. I'll check the ohm level also. I'm about stumpued now except for Your ,Phil's and Kerry's suggestions.

I can't recall what wires are on the starter but I typically jump the heavy battery cable to one of the smaller wires using a screwdriver.
The ground cable is not the one you describe, it's a heavy cable going from the chassis to a bolt on the bellhousing on the bottom of the engine.(I think) I can't remember Phil's suggestion but using a jumper cable from the battery negative post to the engine should resolve any grounding issues.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I tried jumping from the small wire to large bolt. It jumped without a problem.
I took my multi meter and connected it to the negative terminal and the engine . I put it on the buzz selection and it buzzed when touching the engine in a number of places.
I dont know it this could be related but the (dreaded) a/c servo on the 1980 123's Would come on when the key was turned on then stay on for a moment after turned off. I don't recall that ever happening before or could this be related. Stumped Now . Any help on tracking this down. Ignition? Glowplug relay? Any other relay or specific wires to check continuity on ?
I have to say It sparks a lot when jumping the starter!

I'll be checking back all day long to see if there are any other helpful hints THANKS

I know I'm being real technical but I'm chasing ghost I think PIC"S BELOW

I checked for continuity on the glow plug relay with mu multi meter set on buzz and got continuity on 1,2,3,4,&5 post, trying out each post with all other post. nothing buzzed on 6 or 7 with anything.

I checked 1a through 6a and got. 1) using the + on multimeter checking each post with all other post again I got continuity with + on 5a and - on both 3a & 4a.
20 using - on meter the same way I got only a buzz from 4a to 3a & 5a.
DOES anyone know if this is correct or faulty from my attempt.

In the "under dash" pic below by disconnecting the wiring socket and the steering column fastener the ignition assembly should come right out.Is that correct? Is there any particular reassembling tricks involved or will it disassemble and reassemble easily.

I have another as you can see from a pic below. I also just happen to have a complete wiring harness i removed from a parts car and did a continuity check on it from the socket to the 2 wires that connect to the starter and have results if it will help.
any advice is welcome I'm desperate and stumped with my starting dilema.
I'll be back in a little to check on advice if any.
Should I change the tumbler or ignition assembly, or neither.

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If you mean the starter functioned as designed when you jumped the wires, it means your problem is in the wiring system somewhere and not in the starter itself. I think it also means your engine ground is ok.
My money is on the ignition switch, because this is a known failure point.
The servo typically runs for a few seconds when the ignition is turned off.
I think the glow plug relay is irrelevant.

Search on 'starter hesitation' or 'ignition switch' or 'starter not working' and you should find a thread with an explanation on how to clean the contacts in the ignition switch. Or you could try replacing the electric portion of the switch. No need to mess with the tumblers.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I'll first clean the contacts then if nothing I'll try replacing the ignition assembly with the one i have thet was working when I removed it.

Well I've put a starter in,used but it's turned over a few times with it . I put a new neutral safety switch. None of the ignition switches I had matched so I got a new one and still nothing. I'm down to should I get a new starter or a glow plug box. I'm in limbo now. Help

tried this and nothing happened so i guess the grounds are ok

If the starter works every time you jump it at the posts on the solenoid, the problem is not the starter.
I don't think the glow plug system has anything to do with the starting circuit. I'd try jumping the wires at the ignition switch to see if the starter functions using those wires independent of the ignition switch.
Some people have added a solenoid to the circuit to overcome voltage reduction in the wiring. If you search on 'starter solenoid' I think you'll find a thread with a picture of the solenoid added to the left of the battery.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

glo relay should not affect the starter. have you run a redundant ground or cleaned the existing ground cable from body to engine? on my 123 it is below the drivers feet, get at it from under the car.
if that is not it, and it is in the wiring, I personally would install a push button starter switch, with new wiring.

__________________
1984 123.193 372,xxx miles, room for Seven.

1999 Dodge Durango Cummins 4BTAA 47RE 5k lb 4x4 getting 25+mpgs, room for Seven.

the easiest way to settle what it is, is take a small jumper wire and jump from the large upper bolt on the solenoid to the small screw terminal. MAKE SURE CAR IS IN NEUTRAL OR PARK FIRST AND BRAKE IS SET!!! If your starter cranks then you know your problem is elsewhere, if it does not, I would agree you have a sticky solenoid. Could be you just had two tired starters. If your fairly handy you can take solenoid apart and clean and reassemble. I would also look at brushes as well in starter motor.