this makes no sense. I had some shutdown problems with the 300sd a month or so ago, vacuum output was marginal, so I installed a new vac pump. This appeared to solve the shutdown problem; until now. Problem cropped up again the other day - turn the key off and the engine keeps running.

Got out the trusty mity-vac this afternoon and things got interesting. I disconnected the vac line at the shutoff valve. When the mity-vac is connected directly to the shutoff valve the engine shuts down at about 12 in.Hg; this tells me that the shutoff valve is ok. Next I connected to the vac line - turn off the key and the gauge jumps to 23 in.Hg; this indicates what should be more than adequate vacuum to operate the valve. Installed a new connector, line to valve, started the beast, turned the key off and the bloody thing didn't shut down.

I repeated the test procedure three more times with the same results - any ideas would be most appreciated.

Thanks, Jim

__________________
2005 C240 4matic wagon (daily driver)
87 190D - 225K (on loan)
85 190D - 312K (on loan)
2011 Subaru Legacy AWD (Wife's)

Oil in the shutoff valve perhaps...

very interesting problem.

in the vacuum line. When mity is connected directly to valve, two quick pumps, abt 12 in.Hg, shuts 'er right down.

__________________
2005 C240 4matic wagon (daily driver)
87 190D - 225K (on loan)
85 190D - 312K (on loan)
2011 Subaru Legacy AWD (Wife's)

Hm well that rules out the shutoff valve...does it hold vac pretty decently?

Are there any changes going on as far as different pushbuttons pressed at the climate control during the various tests?

__________________
Jim

No changes while testing the shutoff valve. Is there a possibility that the climate control setting might affect the shutoff valve?

Thanks for the response,
Jim

__________________
2005 C240 4matic wagon (daily driver)
87 190D - 225K (on loan)
85 190D - 312K (on loan)
2011 Subaru Legacy AWD (Wife's)

That is possible.
You might start checking the system for vac leaks (ie the line entering the cabin off of the main vac line going to the brake booster).

See if the system will hold decent vac with different climate control settings.

Those vac pods like to go bad

Yes. Since the ventilation system is vacuum operated, a vacuum leak could reduce the vacuum level to the point that it was inadequate to operate the shut off actuator. But if that were the case, you would not likely be seeing 23 in Hg at the shut off vacuum line.

As I indicated above, I didn't change the climate control settings while testing. I did pull a vacuum on the main cabin line and it held with no loss for 2-3 minutes. Perhaps the first thing to try tomorrow would be to change the climate control settings and see if that makes any difference.

What has me puzzled is that the valve appears to work with minimal vacuum, as does the switch (supplying plenty of vacuum to the valve) but, couple the two and nada.

Thanks for the imput.....Jim

__________________
2005 C240 4matic wagon (daily driver)
87 190D - 225K (on loan)
85 190D - 312K (on loan)
2011 Subaru Legacy AWD (Wife's)

Have you tried blocking off all the other vacuum line branch conections except the line to the ignition switch (and the brake booster)? If it works like that, you can add the branches back onto the system until you find the one causing the problem.

I didn't get into general vacuum troubleshooting since the vacuum at the valve was more than adequate (and wifely pursuits dictated that I quit for the day). I will attack the problem again in the morning, perhaps tomorrow will be more productive.

Thanks,
Jim

__________________
2005 C240 4matic wagon (daily driver)
87 190D - 225K (on loan)
85 190D - 312K (on loan)
2011 Subaru Legacy AWD (Wife's)

Regarding the gauge jumping to 23Hg when you turn the key off and are conencted to the line...you might try "t-ing" into the line so that the shutoff valve is connected as well.

Perhaps there isn't enough volume getting pulled to shut the valve off. The volume of the mityvac is very small and vac can be indicated high whereas when you are pulling air from a larger area (the shutoff valve) the high reading would be lower.

Just a thought...

How long will the line to the shut-off valve hold that 23 inHg? It might rear 23 inHg long enough to register then bleed before the shut-off valve can take effect.

Sixto
95 S420
87 300SDL

Yeah thats like similar to what I was thinking.

T-ing into the line would probably be best...you could see exactly what is happening..

I think Craig is leading you down the correct trouble shooting path. I just went through this issue this weekend and finally fixed my problem.
As Craig said, I separated the various systems, even though they sometimes held vacuum. I connect the brown shutoff line only to the main vac line and the car shut right off. I then connected door lock system (yellow and yellow/gray lines). Still shutoff. I then connected the green AC line into the system with the others, and NO SHUTOFF. Now the AC line sometimes held a vac with my Mityvac, and sometimes didn't. My symptoms were almost exactly like yours. Turned out the rubber bladders were split to my main vent pod, and the pod that opens/closes door over blower fan, whatever that is called.
Mityvacs are the BEST! Good luck, keep us posted!

__________________
Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John