my car wont shut off - PeachParts Mercedes-Benz Forum

300duser · #1 09-01-2003, 09:54 AM

1984 300d wont shut off with key, I have to use the manual shut off under the hood, the key will turn off the power but not engine????

300duser · #2 09-01-2003, 10:19 AM

any vucume lines to check?

stevebfl · #3 09-01-2003, 10:29 AM

Has to be volumes on this subject in the archives. Look under vacuum leaks and diesel shut-off.

Basically you have a vacuum leak! Either in the shut off system or such a big leak in one of the other systems drops the source vacuum so low the shut-off can't work.

Simple diagnostics start at the source. The source is the large black line carrying vacuum to the brake booster. There are two small tees coming off. One divides and dives again. That is the one to go for. There will be yellow vacuum lines, green ones and brown ones. Get some golf tees and start pulling lines and plugging them with the golf tees.

The yellow lines go to the door locks which are a likely source of the problem. There will be a "Y" and then a check valve with two yellow lines coming out. Pull the check valve from the side with one line (the source) and plug the vacuum source side with the tee. If the thing still doesn't shut off try the green lines. They go to the A/C door controls. If when all you have left is a brown line hooked to vacuum and going into the dash and still can't shut off, then you need to test the diaphram in the shut-off element. This is at the end of the brown line that goes to the inj pump.

Also one should check the brakes to verify the source vacuum. If the power brakes don't work either then the pump isn't working.

300duser · #4 09-01-2003, 02:35 PM

I did all your tests and no shut off, brakes are ok, but the in line tee that goes to the brake booster looks like it has been cracked and siliconed over I can hear a small hiss when I turn the ignition off, could that do it?

Judge · #5 11-12-2003, 04:29 PM

My car would not shut off either today. Another symptom, just our blocks before I got home and tried to stop the car, the brake pedel got hard, and the brakes worked badly. I suppose some type of vacume problem.

I'm reading the threads now, but in the meant time, where is the manual shut off valve. The car is parked in a two hour zone.

Since I didn't know about the shut off valve, I disconnected the fuel line by the clear filter, and waited until the engine rain out of fuel.

haasman · #6 11-12-2003, 04:43 PM

Judge

Under the hood, on the left-side of the engine, on top if you look closely is a red marking on the linkage. Push and hold until it dies.

Or as someone described finding it "Open hood, stand with toes against driver's side front tire, and look down at the top of the engine. You should clearly see a red lever marked STOP about midway back atop the engine. Push the lever and the engine will stop."

You have a major vacuum problem. Sometimes its from the source, the vacuum pump, and/or bad lines.

CAUTION: Driving a car with disk brakes and no vacuum assist can be VERY scary not to mention danagerous. It requires unusual pedal pressure.

300duser

The hissing is telltale. Often it is simply easier to replace the bad line and/or fitting than trying to fix it. Obviously someone has already tried it and it has failed.

Here is one of many, many posts on the topic: Won't stop

Judge · #7 11-12-2003, 05:05 PM

Thanks haasman,

I feel like duhh. There was only a red sign saying stop. I should have figured this out. Tried it out, works like a charm.

I'm not going to drive the car as is without power assisted brakes, but I'd like to fix it as soon as possible because the parking situation is tight.

haasman · #8 11-12-2003, 05:10 PM

You are welcome.

I didn't see what model you have. Never-the-less it is important to understand why you don't have vacuum. Sometimes it is a line, or a fitting on the line or even the vacuum pump.

If you are having it repaired, be sure and have the service center show you the problem.

Good driving,

Haasman