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  #16  
Old 01-03-2007, 08:23 PM
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Quote:
Originally Posted by stephenson View Post
I checked all the lines, fittings, etc - found no blockages. I cleaned out the solenoid carefully. Put all together and got OK performance, but not nearly as good as when I bypass the solenoid.
Check the switchover valve for leaks?
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  #17  
Old 01-04-2007, 11:27 PM
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TF007,

Interesting question ... I can blow through one port and seal off other and get pressure, but did not pull vacuum through it to check ... I have a Mityvac ... do you know how much vacuum it should hold? Procedure?

Thanks!
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George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg
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  #18  
Old 01-04-2007, 11:56 PM
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Considering that you are seeing a marked improvement with the switchover valve bypassed, it would seem that the valve is either obstructed or leaking internally. Since you have eliminated the obstruction possibility, I wonder if the valve is not completely closed. Or leaks for some other reason, so that some of the pressure that should be transmitted to the ALDA is being partially vented. Or maybe your manifold pressure sensor switch is closed, so that the valve is being opened electrically. (That condition has been reported here in the past.)
I would just pressurize the valve to 10-12 psi and see if it holds. Or use a soapy solution to check for a leak.
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  #19  
Old 01-05-2007, 12:24 AM
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Another interesting point re the manifold pressure switch .. have never checked that. What's best way to test? Check output during normal running or remove and check through switch?

Thanks, again!
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George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg
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  #20  
Old 01-05-2007, 12:25 AM
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Stephenson, my two cents would be to go to the dealership and just buy a replacement. That was my personal choice, although I could see where someone might find that to be a hasty expenditure (it is a $50 part). Bypassing it will guarentee you the improved performance, and leaving the old part on there will likely leave you with the desired protection, but a new part gets you both and saves you a lot of effort. I do not imagine that the solenoid can really be fixed even if you find it has failed (you would have to replace it anyway). Maybe try cleaning/checking electrical contacts first. Bypassing it won't cause an immediate threat, assuming your wastegate is functioning properly. I personally like having the failsafe there. Maybe I wasted my money on new parts, but I got peace of mind and feel good about what's rigged up in there now.

That said, I still have the old solenoid to play with and learn from ...
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1987 300D, arctic white/palomino--313,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--367,500 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--110,000 miles
1995 S320, black/parchment--28,000 miles (Dad's car)
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  #21  
Old 01-05-2007, 12:49 AM
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Good points, BB1957, but will check to make sure electrical input from manifold is good prior to making the $50 leap!
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George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg
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  #22  
Old 01-05-2007, 01:03 AM
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Boost pressure Sensor (?)

Look at post 8 to see what my sensor looked on when I pulled it from the intake manifold on my 1987 300D. Look at post 5 to see what it and the overboost protection solenoid look like new.

The boost pressure sensor is what actually senses the pressure inside of the intake manifold. If it gets too high it sends a signal over to the overboost protection solenoid causing it to vent the pressure signal to the ALDA. If your sensor is junked up like mine was it will not work.

-Jim
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Last edited by Jadavis; 01-05-2007 at 01:09 AM.
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  #23  
Old 01-05-2007, 11:43 AM
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Originally Posted by stephenson View Post
Another interesting point re the manifold pressure switch .. have never checked that. What's best way to test? Check output during normal running or remove and check through switch?

Thanks, again!
The sensor switch provides a ground to the switchover valve. Normally, the switch should be open. It should close only when the intake manifold pressure exceeds the specified value. So the switch should not normally have continuity to ground. Grounding the wire to the switch (sensor) should actuate the switchover valve, so that it vents the ALDA and blocks pressure from the intake manifold. You should be able to hear the valve operate. (Ignition switch on, engine off.)

Last edited by tangofox007; 01-05-2007 at 11:55 AM.
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  #24  
Old 01-05-2007, 11:57 AM
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Quote:
Originally Posted by Jadavis View Post
Boost pressure Sensor (?)

Look at post 8 to see what my sensor looked on when I pulled it from the intake manifold on my 1987 300D. Look at post 5 to see what it and the overboost protection solenoid look like new.

The boost pressure sensor is what actually senses the pressure inside of the intake manifold. If it gets too high it sends a signal over to the overboost protection solenoid causing it to vent the pressure signal to the ALDA. If your sensor is junked up like mine was it will not work.

-Jim

Wow ... I didn't even think to pull the sensor. That's disgusting. Were you able to clean it out, or did you have to replace it with a new sensor?
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1987 300D, arctic white/palomino--313,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--367,500 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--110,000 miles
1995 S320, black/parchment--28,000 miles (Dad's car)
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  #25  
Old 01-05-2007, 01:08 PM
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Yikes - pretty gross find!

I'll check mine ... pretty simple set up, but expensive switch - maybe I'll get lucky8 and be able to salvage ops by cleaning the pressure switch!

Thanks - the pictures really do replace thousands of words!
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George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg
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