oh boy. so some background. I was trying to do a long distance drive a few weeks ago when I stopped to fuel up.When I put the key back in the ignition the starter tried to crank before I even got the key to position two.I took it out and tried it again and small puffs of smoke came out of the keyhole.

On my second attempt to turn it over the starter engaged at terminal speeds, incredibly high pitched screaming.Key was out of the ignition but it wouldn't stop wouldn't stop until I yanked a battery terminal loose.


Replaced the ignition switch that had shorted all, Replace the starter and it's very melted solenoid. But there's a new problem

When I go to start the car the ignition behaves normally, the starter cranks and the engine turns over, and then it immediately cuts out. I've tried giving it a little tap on the accelerator, I checked out the STOP lever and its not stuck or anything unusual. Checked the fuel lines after trying to start and diesel is getting to the injectors.

I'm not good with electrical, at all, assuming thats what this is. Does anyone have any suggestions? I've never had an issue like this with my 4+ 300s.

Thanks very much,

LBJ

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1985 300D Surfblau "Blueberry" 250K R.I.P
1984 300CD Manila Beige "The Banana" 238K R.I.P
1984 300TD Cypress Green "Olive" 390K (M.I.A.)
1982 300D Orient Red "Steak" 195K
1985 Euro 300TD Lapis Blue “Pancake” 200k KM
1982 300D Light Ivory “Butter” 183k
1984 300TD Black “Pepper” 55k

The vacuum shutoff switch on the ignition switch may have the connections reversed.
This would account for your symptoms.
BTDT.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

Agreed, the vacuum connections on the ignition switch are probably reversed.

Ignition switch vacuum hoses mixed up are most likely, considering you were just in that spot, replacing parts. I've also seen a bad lift pump display these symptoms.

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Milan Brown 1979 240D, rebuilt OM617.952 turbo diesel, rebuilt 722.315 transmission (my only daily driver)

Instagram: @maximed93

ok so, its not the vacuum lines. just tried that.


fuel is getting to the injectors just fine, so im guessing not the lift pump?


this car sat for years before i bought it, its been a nightmare.

thanks for the suggestions- any other thoughts?

__________________
1985 300D Surfblau "Blueberry" 250K R.I.P
1984 300CD Manila Beige "The Banana" 238K R.I.P
1984 300TD Cypress Green "Olive" 390K (M.I.A.)
1982 300D Orient Red "Steak" 195K
1985 Euro 300TD Lapis Blue “Pancake” 200k KM
1982 300D Light Ivory “Butter” 183k
1984 300TD Black “Pepper” 55k

The engine stop is entirely mechanical/vacuum operated, there's no electricity involved. Disconnect the vacuum connection at the injection pump and see if you still have the insta-stop behavior.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

ok so i got to messing with the vacuum.

what the hell is going on here:

heres a video of what its doing and what happens when we disconnect the vac

https://photos.app.goo.gl/oXVH1EuowpA926US8

__________________
1985 300D Surfblau "Blueberry" 250K R.I.P
1984 300CD Manila Beige "The Banana" 238K R.I.P
1984 300TD Cypress Green "Olive" 390K (M.I.A.)
1982 300D Orient Red "Steak" 195K
1985 Euro 300TD Lapis Blue “Pancake” 200k KM
1982 300D Light Ivory “Butter” 183k
1984 300TD Black “Pepper” 55k

just posted this vid while you were responding!

__________________
1985 300D Surfblau "Blueberry" 250K R.I.P
1984 300CD Manila Beige "The Banana" 238K R.I.P
1984 300TD Cypress Green "Olive" 390K (M.I.A.)
1982 300D Orient Red "Steak" 195K
1985 Euro 300TD Lapis Blue “Pancake” 200k KM
1982 300D Light Ivory “Butter” 183k
1984 300TD Black “Pepper” 55k

Not sure from the post that the car have been fired up and driven before the failure. It could also be engine hydro lock and stop the engine. If enough coolant leaks into cylinder then the engine will stop.

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

I've been driving it almost year, with several 500+ mile trips, but in general its been a constant nightmare.

its turning over if the vacuum is disconnected.

__________________
1985 300D Surfblau "Blueberry" 250K R.I.P
1984 300CD Manila Beige "The Banana" 238K R.I.P
1984 300TD Cypress Green "Olive" 390K (M.I.A.)
1982 300D Orient Red "Steak" 195K
1985 Euro 300TD Lapis Blue “Pancake” 200k KM
1982 300D Light Ivory “Butter” 183k
1984 300TD Black “Pepper” 55k

Pull off correct vac line from shut off,further down and on back of injection
pump,and on top rear of shut off vac. pot.
If runs,vac. connections not correct or vac leak through on key vacuum switch.

You have two issues. The car starts and then quits before you've had time to move key to RUN from start position (grinding starter noise is the giveaway).

Soon as you break the vacuum circuit the cars starts and continues to run. Reversed vacuum lines going to shut off solenoid on back of injection pump.

The second issue is likely a worn vacuum pump diaphragm, not allowing a quick draw down of the vacuum circuit. Apparent when you hook the vacuum line back up and then try to stop the engine with the key.

A good test of the vacuum system is to get a vacuum tester in line with the vacuum pump. Use the pump to apply vacuum to the line and see what it will draw down too.

The second test is to follow the vacuum lines from the key switch. One will go to the fuel shutoff on the back side of the injection pump. Get the car started like in the video, and using the hand held vacuum pump connected to the line going to the shutoff solenoid. Pump the unit and the car should shut off. If it does not, double check the vacuum line for correct routing and leaks. If you are sure you have the correct line and you can create a vacuum with the pump and the car does not shut down. It is the solenoid. If the handheld unit makes the car shut off the vacuum pump needs a rebuild.

report back findings

dodgeit- Thank you for your comprehensive reponse. I messed around a bit before I saw your message, so I'm going to post my findings of what I did and then take it from there
-------
Disconnected vac at the injection pump, starts no problem, plug it back in, car shuts off.

Disconnected brown ignition line that goes through the firewall at the Y connector, plugged off the y, starts right up, plug line BACK in, continues running but key will not shut it off.

disconnect both vacuum lines at the ignition, starts up, runs, drives, if i press them together to close the vacuum (please see lovely illustration), car shuts off. (well, it was, but after driving for an hour and a half and car got hot it didnt shut it off, but engine slowed, had to use cut off switch under hood)



so, the starter switch was replaced, not the whole assembly. I'm thinking that whatever part is in there that separates the vacuum in and vacuum out got blown up with the original incident happened ( smoke coming out of the ignition)

This seems reasonable yes? but why wouldn't the two vacuum lines pressed together fail to shut the car off when hot?

Attached Thumbnails

 

__________________
1985 300D Surfblau "Blueberry" 250K R.I.P
1984 300CD Manila Beige "The Banana" 238K R.I.P
1984 300TD Cypress Green "Olive" 390K (M.I.A.)
1982 300D Orient Red "Steak" 195K
1985 Euro 300TD Lapis Blue “Pancake” 200k KM
1982 300D Light Ivory “Butter” 183k
1984 300TD Black “Pepper” 55k