Car wont shut off AT ALL! - PeachParts Mercedes-Benz Forum

snookwhaler · #1 12-05-2009, 05:34 PM

Man.... Every week it is something with this car. I went to put the new (used) rear end yesterday and gave up because of the rain.

Today the wife has it out driving around shopping. She pulls into the parking lot and the car won't shut off. So, she opens the hood and hits the stop lever to shut it off. No problem, I'll deal with it later. So, then she goes to go to a different mall and no brakes. She pulls it into a parking space to shut it off and it will not shut off with the key. So, she gets out to hit the stop lever and it is difficult to shut off there too? Had to block the intake with a rag. What gives?

So, she gets home and same problem. I grab my mighty vac and check for leaks. A/C no problem, door locks good, reservoir no problems, modulator bleeds off but VERY, VERY slow, VCV no problems.

What do you guys think? A problem with the large vacuum supply line, vacuum pump, brake booster failed internally?

Mazootpusher · #2 12-05-2009, 06:01 PM

Well you know the basics I'm sure, just you are a little fed-up with this vehicle right now.
your thoughts are all over. Grab your vacuum Gauge, and start by checking the main vacuum line
to see what kind of vacuum your pulling, it could be a bad vacuum pump check valve,for a start ?

snookwhaler · #3 12-05-2009, 06:05 PM

Quote:

Originally Posted by Mazootpusher

Well you know the basics I'm sure, just you are a little fed-up with this vehicle right now.
your thoughts are all over. Grab your vacuum Gage, and start by checking the main vacuum line
to see what kind of vacuum your pulling, it could be a bad vacuum pump check valve,for a start ?

That brings up another question that I never really thought of until now. The vacuum for the transmission transducer comes right off the main line before the check valve. Everything else comes off the main line after the check valve. Is this right? It looks right by the vacuum diagram, but I have removed some things (EGR and ARV).

Also, what should vacuum be off the main line before the check valve? 20 in.HG? More or Less?

Edit: OK... I just went through the entire vacuum diagram. According to what I read, the vacuum transducer for the transmission should in fact receive vacuum after the check valve and all of the accessories should receive vacuum from the main line BEFORE the check valve. So, it is backwards. But, it has worked fine since I have owned the car. The PO replaced a lot of vacuum tubing under the hood and probably screwed it up. I should have checked it all when I removed the EGR/ARV lines. Still it worked before. So something is still wrong. I'm going to do some more troubleshooting in the AM.

81Wagon · #4 12-05-2009, 07:02 PM

The stop lever has nothing to do with the vacuum system, so if that wasn't working you've got another issue... I don't have too much experience with the fuel system so maybe someone else can chime in, but the depressing the stop lever should cut off all fuel to the IP so there's no way the car should keep running. Either your throttle linkage is out of whack, your engine is sucking in oil from somewhere, or whatever valve in the IP is supposed to be cutting off the fuel isn't doing its job.

snookwhaler · #5 12-05-2009, 07:21 PM

Quote:

Originally Posted by 81Wagon

The stop lever has nothing to do with the vacuum system, so if that wasn't working you've got another issue... I don't have too much experience with the fuel system so maybe someone else can chime in, but the depressing the stop lever should cut off all fuel to the IP so there's no way the car should keep running. Either your throttle linkage is out of whack, your engine is sucking in oil from somewhere, or whatever valve in the IP is supposed to be cutting off the fuel isn't doing its job.

That is what I thought. She could not say if she pushed the STOP lever all the way to the valve cover or not. I suspect that she only pushed it half way. I just went out and did this after my drive and it stops immediately with the lever. I forgot to post that above.

This is frustrating because now this means that it is intermittent.

81Wagon · #6 12-05-2009, 07:53 PM

When you ran the climate control unit, did you hit every single button? If there's a leak in one of the vacuum actuators (or the solenoid valve they're connected through) it might only show up on certain settings. And even then it might only happen for a few seconds (I guess the CCU will turn the solenoid back off after enough time to open or close the actuator has passed).

At least, that's how it worked for me when I was troubleshooting the shutdown problems my 300SD was having. It was quite frustrating tracking down the leaks! It turned out three of the solenoid valves behind the climate control unit were leaking like crazy. Replacing them fixed all my problems (but I never had any issues with my brakes).

79Mercy · #7 12-05-2009, 06:02 PM

Sounds to me like the vacuum pump is shot.

Remove the brake booster vacuum hose and plug all other vacuum ports and check for vacuum at the end of the main hose.

tankowner · #8 12-05-2009, 06:02 PM

Can you replicate the no shut-down in your driveway. If so you can troubleshoot the vac system from there. Could be the pump I suppose, but may just be leak somewhere else (although, it sounds like you covered some ground there). Make sure you don't have any oil in the vac lines that might be screwing with things. You might pull the instrument cluster and test the shut off valve at the ignition - but if you are having brake problems too, it probably isn't that. Hmmmm.

Jeremy5848 · #9 12-05-2009, 06:28 PM

At least 20" Hg and could easily be 25" Hg with a good pump and no leaks. You can also check the vacuum shutoff on the IP using a Mityvac to make sure the shutoff is working. It has a diaphragm that can leak/rupture.

snookwhaler · #10 12-05-2009, 06:53 PM

Quote:

Originally Posted by Jeremy5848

At least 20" Hg and could easily be 25" Hg with a good pump and no leaks. You can also check the vacuum shutoff on the IP using a Mityvac to make sure the shutoff is working. It has a diaphragm that can leak/rupture.

Thanks. I was not sure of those #'s. I did not check the shut off valve (duh

). I should have checked that first. I forgot in my panic.

I switched those 2 lines around on the main line and went for a drive (could not wait till morning). I ran the defrost, the heat, cycled the locks about 20 times and shut if off with the heat on and it shut right off? I did it several times and it shut right off. No problems with the brakes and no oil in the lines either?

I don't know. I'll do some closer looking in the daytime.

SD Blue · #11 12-07-2009, 01:00 AM

I believe you have the same vacuum pump as mine. Believe me, it's very simple and straight forward. The hardest part is pulling all of those small hex drive screws holding the pump on the block. (The check valve portion can be rebuilt with the pump on the engine but I removed it to inspect the major mechanicals of the pump.)

micalk · #12 12-07-2009, 07:50 AM

Bouncing guage is due to bad check valves in the pump. It should be steady once it builds pressure but the check valves are allowing vacuum to escape. As SDBlue said it can be done with pump on car, just remove the front plate (flat blade screws.) Hardest part is placing gaskets properly while pump face is vertcal.

snookwhaler · #13 12-11-2009, 06:07 PM

The car pulled this crap 2 more times today. I got the rear end fixed, so we have been driving it a lot more. I put about 200 miles on it today and it was slow to shut off 2 times out of about 20 along with weak brakes.

What is involved if I pull the pump off the block? I want to take it off and inspect the entire pump. I see that the kit does not come with that particular gasket (block to pump gasket). Should I go ahead and order that gasket separately? Or can I reuse the old one? Is there any kind of special alignment I need to do for removal and re-installation?

I went to whunters recent re-post on vacuum pumps and went through a bunch of threads. I found one that describes the procedure pretty clear on how to handle the rebuilding the pump itself. No pictures but sounds pretty easy.

micalk · #14 12-11-2009, 09:38 PM

Here's the problem with removing the entire pump. You have to push against a stiff spring in order to get the piston out. The manual calls out a special tool to mount the pump onto for this purpose. If the pump is left on the car, you can rotate the engine to do the same task. If you're bent on removing the entire pump, here's what I would do. Pull the front cover (flat head screws). Turn over the engine until the piston is just past its apex and is starting to return. Remove the nut holding it in place and then keep turning the engine so the bolt withdraws then just begins to come through the center of the piston again. Jack the piston over just a bit so the screw gently wedges in the hole and pushes the piston out of the cylinder far enough to remove it. Replace the O-ring and sleeve, wipe out the cylinder bore, lubricate it and the piston with clean oil, and return to piston to the pump and secure the nut in place. Now remove the pump and replace all the check valves and gasket and reassemble. You will need a new gasket for the pump, wouldn't rely on the old gasket - too much chance for a leak and it's cheap insurance.

I don't know how hard it is to push against the pump spring, maybe it's not that bad. If the vacuum guage is bouncing like you say, then your piston mechanism is fine - spring, piston, etc., so removing the pump from the engine will likely not reveal any surprises. It's a little tricky to replace the check valves and gasket while the pump is installed because of the vertical face, but if you put the car up on ramps the pump/engine will be tilted enough for everything to stay in place. It may save you time and money if you can do it that way.

snookwhaler · #15 12-12-2009, 08:36 AM

Quote:

Originally Posted by micalk

Here's the problem with removing the entire pump. You have to push against a stiff spring in order to get the piston out. The manual calls out a special tool to mount the pump onto for this purpose. If the pump is left on the car, you can rotate the engine to do the same task. If you're bent on removing the entire pump, here's what I would do. Pull the front cover (flat head screws). Turn over the engine until the piston is just past its apex and is starting to return. Remove the nut holding it in place and then keep turning the engine so the bolt withdraws then just begins to come through the center of the piston again. Jack the piston over just a bit so the screw gently wedges in the hole and pushes the piston out of the cylinder far enough to remove it. Replace the O-ring and sleeve, wipe out the cylinder bore, lubricate it and the piston with clean oil, and return to piston to the pump and secure the nut in place. Now remove the pump and replace all the check valves and gasket and reassemble. You will need a new gasket for the pump, wouldn't rely on the old gasket - too much chance for a leak and it's cheap insurance.

I don't know how hard it is to push against the pump spring, maybe it's not that bad. If the vacuum guage is bouncing like you say, then your piston mechanism is fine - spring, piston, etc., so removing the pump from the engine will likely not reveal any surprises. It's a little tricky to replace the check valves and gasket while the pump is installed because of the vertical face, but if you put the car up on ramps the pump/engine will be tilted enough for everything to stay in place. It may save you time and money if you can do it that way.

Ok.... Thanks for the info. I'll do it on the car if my back holds out that long.

I did not know I could replace the piston seals without removing the pump. That was my main concern. That and cleaning/lubing the bore.