Help! 1982 300d turbo stall problem.
 

Hello! I just joined. Any kind mechanically inclined people out there willing to help a mechanical moron? Hope so. If anyone does respond, please be patient with me--I'm no mechanic.

So, my a/c blower on my '82 300d turbo quit working and I decided to replace the ignition switch along with the tumbler. I removed the instrument cluster, did the job, then put everything back like it was, paying particular attention to the vacuum lines running from the ignition assembly...and, the a/c worked!:)

But, when I started the car, it ran for about 2 seconds and shut off.:( Next, I changed both fuel filters, undid the pressure release valve on top of the main filter housing and worked the manual pump to let the air out of the lines...and the car started!:) I let it run for a while in preparation for an oil change and then shut it off for a bit. When I started the car again, the run-for-2-seconds-and-stall problem was back!:( And it stayed back.:mad:

Before I worked on the ignition, the car started up and ran just fine. So, it seems like I must have done something wrong. But I don't see how I could have caused the problem working on the ignition and instrument cluster area. Could the new ignition switch be faulty? Could I have unknowingly messed something up near the driver's-side dash that would cause this? The only really stupid thing I did was start the car up before I reinstalled the oil pressure line to the back of the instrument cluster causing a small bit of oil to shoot out onto the floor. I switched the 2 vacuum lines on the ignition assembly just to be sure I didn't mix them up--didn't help. Anyone have any ideas?

disconnect the vacuum line from the fuel cutoff on the back of the injection pump. If it still shuts off your problem is not in the ignition switch. It sounds like you have an air leak in the fuel system to me.

The shutoff is controlled by vacuum. I believe it's vacuum applied (as opposed to vacuum removed). Somehow I believe that you are applying vacuum to the shutoff with the new switch.

try this (with the hood open - to use the manual shutoff) plug bothj vac lines going to the ignition switch. Start the car. If the car continues to run use the manual switch to shut it off,,, Now hook the lines back up, does it stall again? If so,,, gotta be the ignition switch, if not you fixed it without doing anything.

now if the car stalls with the 2 vacv lines to the igntion switch plugged, I would look towards the fuel system,,, Good luck.

Marty

Thanks, guys. That gives me a place to start. I'll try your suggestions tomorrow after work and let you know what happens. By the way, the problem started before I ever did anything with the fuel filters and lines. Makes me think it must be some vacuum-related problem or the ignition switch...then again I really have no clue. Maybe I should replace all the fuel lines and tighten the injector lines? Is a bad ignition switch capable of causing the problem? Maybe I should try crimping the 7 connection points in the plug that plugs into the ignition switch to make a better connection? I'll just mess around with the things you mentioned and see what happens. Told you I was a mechanical moron:confused:.

Ok, after removing the wasp nest that appeared under my hood (a nice-looking wasp--orange with blue wings, but kinda cranky), I disconnected both vacuum lines running through the firewall from the ignition and plugged them with nails...and the car runs!:) It doesn't run when I put them back into the connection points.

So, does this mean I have a faulty ignition switch (electrical part)? I just bought the darn thing. Before I send it back, is there anything else anyone can think of that it could be?

I should mention that when I removed the original switch for replacement, I butchered the round plug (split it in two like a sandwich) that attaches to it and had to find a wiring diagram to figure out which color wire went into which plug socket. Then I snapped the plug back together. I triple-checked that the wires were as indicated on the diagram. The only thing is that there are two plain red wires that went into the two holes marked "30." It doesn't matter which red wire goes where, does it?

Thanks for your help. This forum is da bomb. Gotta run but I'll check back later on today.

Are you sure you did not reverse the vacuum connections on the ignition switch? Ignition switch on, there is supposed to be no vacuum to the shut off valve. Switch off, vacuum to the valve, engine stops.

I'll double-check the vacuum lines, but when I couldn't start the car I switched the lines--it didn't seem to make a difference.

lemur,

Here's what Id do having just done this:

1.) Test iginition shut off. With car running (disconnect your vac line to shutoff), attach mity vac directly to shutoff. Pump mity vac, car should shut off quickly. If this works, then the shut off works, on to step #2.

2.) Next you need to test the vacuum signal that is going to your shutoff valve. Connect a vac gauge (mity vac will work here too) to the vac line that would otherwise go to the shutoff valve. Turn on the car. If there is a vacuum being pulled on that line while the engine is running you have found your problem. I suspect this is the problem from your description. It sounds like the car takes a minute to charge the vac system, and as soon as it does, has enough to pull the shutoff valve shut...shutting off the car.

If you are sure you reconnected the lines correctly, you may have installed the tumbler with the ignition switch internal portion 180 degrees wrong. I did this a month ago, but I caught it on a bench test. It would give you these weirdo shutoff problems, and it feels semi normal with the key. I dont know if I could have gotten it all the way back into the car like this, but it is worth a look.

If you think this is the case, I have some pictures showing the 'right' way from my ignition switch tear down and rebuild.

dd

I'll check on that flipped tumbler possibility. I don't think I put it in upside-down, but you never know. Don't have a mity vac, but I'll look into getting one. Ok, now I really do have to go. Thanks for your help, everyone. Back later.

Did you replace the whole steering wheel lock assembly? It sounds like the valve in your ignition must have a leak. It is not an electrical issue.

Thanks, bgkast. Hmm...not an electrical issue. So I guess I should keep the electric portion of the ignition switch that I just installed?

No, I did not replace the whole lock assembly, just the electric portion of the ignition switch and the tumbler part (the tumbler was getting loose and I heard horror stories about the whole mechanism locking up if this isn't fixed quickly enough). The problem didn't exist before I did this.

How would I go about testing the ignition valve? Is this an easy fix? What exactly is the ignition valve? Is it the part of the ignition assembly with nozzles that the two vacuum lines plug into, I suppose? I'm new to this working on my car stuff, but I'm learning.:o

Oh, and thanks dieseldan44. I don't have a vacuum pump but I'll try to think of some kind of variation on the test you suggested.

lemur,

you are going to need a vacuum pump for this, and for lots of other stuff if you continue to work on the car. i use it more than any other tool except the socket wrenches.

the MityVac Silverline kit at $70 is the way to go IMO...you wont regret it.

dd

I'll start saving for the mitivac (I'm in grad school and broke). The 4000 kit looks good. Is the 4050 mityvac worth the extra cost? That one comes with more goodies and a dual meter for just a little more money.

It's good that I was able to narrow the problem down to vacuum issues. I suppose if I wanted to drive the car now I could keep the lines disconnected and plugged and use the manual shutoff--hey, maybe I could rig up a cable-and-pulley system through the firewall that would pull the shutoff without having to open the hood...ok, I'm getting stupid now...

Dude, that ain't stupid. When I was shopping for my Benz, I looked at one that had that exact setup. It's a shame the owner just didn't understand the vacuum system and gave up on fixing it correctly. Keep working on this and good luck. You'll get it going. If you have a good relationship with a local indy mechanic, maybe for the short term you could see if you could borrow a mightyvac. Long term you should own one, but if money's tight.... I borrow tools from my indy all the time.