Well I have spent alot of money on my Benz (1980 300CD), but I am starting to get a bit peeved and hoping someone can lead me in the right direction.

My ignition locked about 2 weeks ago... we tried everything on the thread but in the end, it had to be towed. A week later the new tumbler is installed and we have a new problem... according to my mechanic, we have lost vacuum pressure from the back of the pump. I am waiting for him to get me a list of what is not working, but does anyone know of a connection between the vacuum pump failing and the tumber/lock on the ignition being replaced... I find it almost impossible to think that my vacuum (just rebuilt about 3 months ago) is shot...

He is currently referring to a rod from the back of the pump.. .I will update as I get a parts list generated. Any thoughts would be greatly appreciated.

Thx,

Rob

If the pump really was rebuilt (properly) it shouldn't have failed in 3 months. Remember though, a 25 year old car will continue to have mechanical failures and unrelated, nearly simultaneous failures of 2 or more systems will happen.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

Hi, The vacuum system is directly conected to the ignition switch on your car. A vacuum line from the vacuum pump runs to the back of the ignition switch, then to the fuel cutoff valve on the back of the injection pump. When you turn off your ignition, the vacuum valve on the ignition switch opens. This provides vacuum to the injection pump cutoff valve which stops the fuel flow to the engine. If the vacuum lines are not correctly connected and leak tight, the engine will continue to run when the ignition switch is turned off.

It seems unlikely (but possible) that your vacuum pump failure was coincident with your ignition switch failure. I would recommend double checking all the vacuum conections, including the connections on the back of the ignition switch.

Good luck.

Well according to my mechanic a rod is through the pump and I need a new pump... I don't really know what the heck he is talking about... his shop has taken great care of me and my mercedes over the years... just looking for some idea of what happened... we all are a bit unsure.

Thx

sounds like he is unaware of the vac lines to the switch. hope he is not trying to cover up his unawareness with suggestions of unrelated work.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Was the car shutting off correctly before the problem with the ignition lock? If so, it seems like too much of a coincidence that the vacuum pump failed at the same time as the ignition. I guess anything is possible. Hopefully, the mechanic did not mess up the vacuum pump while trying to troubleshoot the ignition issue. However, if the vacuum pump has failed it will need to be repaired. I guess it comes down to how much you trust him.

you know, everything was working fine... that is why I have been so stunned about it... Does anyone have any idea how the vacuum pump could get screwed up by fixing the ignition? Could it just be unhooked?

Thanks again for all the comments.

Rob

It's quite straighforward to check a vacuum pump. Simply remove the vacuum hose to the pump and attach a vacuum gauge. If the gauge reads 20" or more, the vacuum pump is not the culprit.

How are the brakes? Without vacuum, the brake booster won't work and you will have difficulty stopping the vehicle.

I'm going along with Brian on this one. Follow his suggestions. Also you are not very clear on your explanations. You stated that your vacuum was rebuilt about 3 months ago. How do you do that?

Peter

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Auto Zentral Ltd.

It appears that this is a mechanical failure... we are getting no vac. pressure... fortunately the engine is fine and it doesn't appear to have effected anything else (I read some other threads last night and was worried)

If anyone knows where to p/u a used one cheap, or even a new one I would be interested in knowing.

THANK YOU!

Rob