Need help on testing the various vacuum componets on a '91 2.5. I know there must be a good link for doing so but I can't locate it. It needs to be
"vacuum testing for dummies". Know the first thing I need to do is purchase
a mitty vac. Thanks

What exactly in the vacum system are you having problems with? Yes, the Mity Vac is a must, I have one it is perfect for testing system. Are you having problems with the locking system, climate control, etc? How are your brakes? Do you have to apply more pressure to the pedal to get the car to stop, or does it get harder and harder to push pedal as you "pump" the brakes?

Get a mity vac and start testing,

http://www.peachparts.com/shopforum/showthread.php?t=105297

__________________
1984 300SD Turbo Diesel 150,000 miles

OBK member #23

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Thanks Compress Ignite, are these for the 124 body? Dieselnutnj I want to make sure the vacuum pump is putting out what it should. Also turbo is not providing boost it should. Have the link for testing the vacuum transducers. Also transmission does not shift like it should...believe this is due in part to the turbo problem. Vacuum module for it may be suspect. All help is appreciated!

When I disconnect the line to the vacuum modulator on the transmission there is no change. What's up?

Is, You describe the automobiles problems,symptoms,aliments,Etc.
[And we try and guess (Sometimes based on the Moon Phases) how you can fix it.]

If you disconnected the vacuum to the Modulator on the left hand side of the Transmission
and there was no change in the Transmission's performance...
Yes you have a vacuum problem...
Are there any other vacuum dependent devices "Not Feeling Their Oats"?

Let me back up...The EVIL EDS (ELECTRONIC DIESEL SYSTEM) computer
[lives behind the Battery,behind a removable plastic "Wall"] will deny you
BOOST based on almost any of about 15 different scenarios.A lot of the
foolishness can be eliminated with GSXR's Pressure Operated Wastegate
Actuator swap.[AND blocking off the EGR "for Testing" with BC's "Kit".]

It's early enough in the Morning for me to go out on a limb and suggest
that your lack of Boost may be related to a Vacuum issue.

Or the little pressure line that allows the ALDA to enrich the fuel flow along
with Boost may be clogged .(in which case you may have Boost ,BUT not
the added Fuel to go along with it.)

Lots of Fun Ahead...Step by Step...And breaks when it stops making sense.

__________________
'84 300SD sold
124.128

All the vacuum info received, thank you, seems to be for the 123 & 126, does anyone have the vacuum system diagrams for the 124? What should the vacuum pressure be to the tranny modulator? If pressure is OK, is the next logical step to replace the modulator?

Everything to the ALDA is clean and clear. Codes have not been checked on the ECU. That's another step for this process. Thanks

Modulator vacum varies with throttle setting and load. There is no one specific set level of vacum. If you ever looked under the hood of a 123 or 126 Turbo Diesel, you'll find a "black box" on the valve cover. In it is a miriad of vacum switches, designed to change the vacum at the modulator to simulate a gas engines vacum system.

With no vacum at modulator, try moving the throttle as you check it. Maybe at idle which is where I think your checking there wont be, although I think there should be.


Negative wind.. I like that!!!!!

Nope, the black box is ONLY for the EGR. The vacuum valve on the top rear of the injection pump is actually what changes the vacuum.