Shut off issues
 

I have some issues shutting the car off. I guess it is called runaway diesel but it doesnt keeping running strong, it shutters like it wants to but doesnt stop. Sometimes it does shut off though as there isnt an issue but lately it hasnt been shutting off more and more. I thought I had a vacuum issue and I think that I addressed it down some posts. I bypassed the egr and replaced every rubber hose I could find with the rubber hose from an auto parts place. The transmission seemed to work a lot better at first but then the non shutoffs came back and it seems that the transmission is hitting hard again. So, is it the shutoff valve that needs replacing? Like I said, it shuts off sometimes, studders sometimes, and just keeps on running sometimes.

DK

PS: I have done some searching on here but havent found the same symptoms that I have. Maybe my symptoms are leading to a runaway diesel all the time?

DK, I just joined the forum and also just started having runaway problems with my 300 D (only mine doesn't shudder - it just keeps running great). I'll be interested to see what we learn.

First Doug, you do not have runaway diesel. That is when the engine is fed a fuel supply, and races at max rpm's until it basically blows itself apart. Very scary scenario......
You just have a failure to shutoff, which is unbelievable common, and just about every scenario is covered in the archives 20 times apiece.

best bet it to first look for an obvious vac line undone under hood. Seeing none, find golf tees, or similar, and remove and plug vac lines near firewall that are yellow, yellow/gray and green. Basically you just want the brown line still connected, which is shutoff. The small black vac line is a vent. Also plug vac line heading down towards tranny.
See if car shuts down then. If it does, then plug back in the lines one at a time and see when the car doesn't shutoff. Then trouble shoot that "circuit".
You will want to get a Mityvac, or some other device to measure vacuum. They're about $28 to $34 bucks for the plastic kind, which work perfectly well.
Report back. Your failure to shut off and hard shifting let us know you have a vac leak somewhere, or a failure to generate vacuum from pump, but since you didn't mention you had rock hard brakes, we'll assume that isn't the case.....

Simplest test is to hook a vacuum source (Mity Vac is a good choice) to the shut off valve while the engine is running and see if pulling a vacuum will shut the engine down. If it does, the vacuum problem is elsewhere. If it doesn't, the shut off valve is bad.

I bought a mighty vac for my other issues but after replacing all the rubber lines and the car seemed alright, I didnt end up taking it out, so I brought it back. Looks like I will be going back. AND, I do have rock-hard brakes. Especially at low rpms. Is this bad? I was getting worried about them before but they have stayed on the back burner as the brakes work okay above around 20mph.

DK

Sounds as if your brake booster is failing, drawing a lot of vacuum and depleting the system's vacuum resources. Perhaps it could be a bad vacuum pump.

Ut oh,
How do I test for a bad vacuum pump?

DK

First put the mity vac on the main vacuum line and see how much it is pulling. If low, connect the mity vac directly to the pump, bypassing the brake booster and everything else and see how much the pump is pulling with nothing attached. If it's pulling a good vacuum, suspect the brake booster.

It turned out to be a couple of vaccum leaks. Thank god!!! I tested all the hoses and parts of the car and they all worked out pretty well except for the lines that go to the ignition and the air control. The air control was the worst so I plugged the end of the line and the car shutsoff BEAUTifully. It also shifts like never before since I have owned the car. SO, does anyone know what I should do about the blower control? (Heck, I dont even know what that mess of hoses is under the middle console) I want to take car of that part first because it appears to be the main issue. Then I will try to find out what issue the ignition has.
Thanks so much, especially kerryedwards for all the help and preventing me from ripping my whole car a apart without testing it for some simple things first.

DK

First test: reattach the vacuum line to the climate control, then push the far right button, shutting off the climate control. If this solves the vacuum leak, the problem is in the pods or switchover valves in the climate control system.
It's probably one or more of the vacuum pods in the climate control system. You'll have to check them one by one. There's one for the footwell vents to the right of theaccelerator, there's one that controls the center vents, there are a couple more also.

I checked them all over and found that all the pods on the unit were fine but there is a hose that is green that goes up to a "door" in a air tube under the passenger side left foot area. I dont really want to go and mess up anything up so I just plugged the hole where that hose was suppose to be and I am leaving that disengaged until I have the time and feel comfortable working on that area of the car. The car seems to run fine.
I checked the vaccum pressure now and it rests around 7.5 to 10 at idle and then rises when I accelerate to 3500 rpms (with the vehicle in park) But hitting the break pedal really brings down the vaccum. Should it do that? Hitting it consecutively five times brings that vaccum pressure down to 1 or 2. Is this normal or is there a leak with the brake booster?

Thanks again,

DK

Vacuum should be 23 or better......
 

Your vacuum should be 23 or better with only the brake booster connected....everything else plugged.......

you either have a weak vacuum pump.....or a bad brake booster.....from what I can tell from what you have told us so far......

SB

I think you may be right. When the car is put into higher rpms the vaccum goes higher and then drops when the car is set at idle. Should I go rebuild or is it just easier to take a vaccum pump off one of two of my parts cars?

DK

You need to verify the vacuum on the main vacuum line from the pump, with nothing else connected to that line. Report back with the vacuum at idle. It must be disconnected from the brake booster when you perform this test.

The culprit can be the pump.......or the booster.......still don't know which at this point.

Okay, the results are in:
At startup at idle: 7"
A couple of minutes later: staying strong at 9"
At 1500 rpm 14.5"
At 2500 rpm 22"
At 3500 rpm 22"

I got these readings by disconneting the line going to the brake booster and clogging all the vaccum lines going to the rest of the car.

On a side note,
I also put vaccum into the brake booster line and brought the vaccum up to 15" (it took forever) and it held for about a minute. It has stayed at 15" for about 10 minutes now.

I think that it is the vaccum pump but that is why I am here. :)

DK