I have started going through the troubleshooting guide on my 1985 300D

http://www.mbz.org/articles/trans/diesel.html

and have not met the criteria of the following items -
a) Instruction #6 in the article - I put the vacuum pump on the line going down to the green vacuum box on the side of the tranny and it does not hold the same amount of vacuum for 5 minutes. I will check the line and then replace the vacuum box as necessary. Does it sound like I need a new vacuum box since it "leaks down" (assuming the line does not have any problems)?
b) Instruction #7 in the article - I disconnected the linkage to the regulating valve at the injection pump lever (ball joint) and with the engine at idle I moved the lever on the regulating valve to full throttle position (or in that direction anyway) and the engine was no longer at idle. I must be missing something because my vacuum pressure dropped very slightly and then it went negative approximately 20" Hg. It never did go to 0 like the write up says it should. Is this write up for a non-turbo engine? What am I doing wrong? Can this cause the tranny to shift into high gear at low speed? I have already adjusted the Bowden cable per the directions.
I will proceed after these items are in correct order.

Thanks,
Jim
'85 300D
'95 E320
'97 CRV

The modulator doesn't need to hold vacuum for five minutes for the trans to shift properly. I have never heard of this criteria. I suppose that the check is valuable though as the possibility to suck trans fluid or other debris into the line (and valves and orifaces) if there is vacuum flow.

The second question is harder. I presume you are talking about the vacuum proportioning valve. I presume the instructions are to disconnect the valve from the throttle linkage so that the valve can be moved with the vacuum (engine running) without the engine reving. If the throttle moves in this condition you really haven't disconnected it ("I moved the lever on the regulating valve to full throttle position (or in that direction anyway) and the engine was no longer at idle"). The point to this is to see the range of vacuum control. With a vacuum source (engine running) the vacuum to the modulator should go from high (10in or higher) to zero as the valve is moved by hand. The valve is disconnected by either removing the plastic clip at the top or by popping off the ball socket at the bottom.

And YES if your vacuum were to increase instead of decrease with throttle your shifts would happen earlier.

I got out and messed around with it some more. I was disconnecting the wrong linkage :(

Anyway I disconnected the correct linkage and moved the vacuum proportioning valve until it was 10 mm from the stop. I could only adjust the vacuum to drop to 7.5 " Hg. During the test drive it seems that the car takes a little longer to shut off.

Is this an indication of the proportioning valve needing replacement?

thanks,
Jim
'85 300D
'95 E320
'97 CRV

If it is the vacuuming proportioning valve
 

is this the same as the injection pump vacuum valve?
thanks,
Jim
'85 300D
'95 E320
'97 CRV

On the back of the injection pump is a valve that I call the proportioning valve. It is a controlled leak, proportional to throttle movement.

Where are you taking the vacuum reading? What is it at idle? How does it change as you move the valve linkage? If verything is correct the valve should make no difference, because the throttle is at idle and the micro-swicth is not feeding the vacuum to the proportioning valve. Try moving the throttle link (do not raise engine from idle). When the micro switch engages there should be a significant drop in vacuum. If you hold the throttle in this position and move the proportioning valve linkage the value should go to zero at full throttle.

What do you have??

None of the transmission vacuum should have anything to do with how long it takes to shut off! They should be on separate vacuum circuits with the source being the only thing in common.

I am hooking the test gauge up to where I disconnected the line going to the tranny. It is the round blue thing (I think called the proportioning valve on this model) mounted on the drivers side fender. Anyway, after trying it again
I have observed the following:

a) Idle with no adj. of injection vacuum controller lever = approximately 16.5" Hg.

b) Pull the lever up on the fuel injection vacuum controller and it drops to 9" Hg - this is as low as it goes. If this is supposed to go to 0" then this could possibly be the cause of my poor shifting performance. Doesn't look like it will be much trouble to replace.

How does the round blue thing on the drivers side fender fail and what is the correct name?

Testing has ended for this weekend because I accidently broke the fitting off of the brake booster vacuum check valve - durn.

thanks
Jim
'85 300D
'95 E320
'97 CRV

Ooops! I forgot you had an 85 model.

The blue thing is a vacuum amplifier. With this device the value at full swing on the proportioning valve will not go to zero at idle. I would think it should go lower than 9in.

The difference with the amplifier is that the amplifier takes the amount of boost into the equation. If you put a long line on your gauge and watch it while someone else drives, you will see that full throttle will drop the vacuum to modulator to a value (9in in your case) and as full boost is achieved the vacuum should deminish to zero.

Your line breaking might have been a blessing as the standard reason for the vacuum being too high is the supply oriface having been reamed too large. This happens because soot gets into the oriface and plugs it. Cleaning it too vigorously enlarges the hole and supplies too much vacuum.

I guess the next step is to "tee" off of the line going to the tranny and while riding in the car watch this pressure. It should go to 0" Hg as the accelerator is put to full throttle while driving down the road. If it does not does this mean the vacuum amplifier is inoperative?


thanks
Jim
'85 300D
'95 E320
'97 CRV

pressure readings are as follows
 

I "teed" into the line going from the vacuum amplifier to the tranny and took if for a test drive. Numbers are as follows:

I can touch the throttle and I see an immediate drop from around 15-16" Hg to aproximately 10. I continue to floor it and the pressure will drop down to around 6.5"Hg and this is as low as it goes. Just cruising along at around 60 mph I am showing around 16"Hg.

I jury rigged the brake booster vacuum line check valve nozzle to allow me to continue the test. I will run the test again after I replace this item. I do seem to recall maybe "cleaning" this line out early on.

I have already tested the injection pump vacuum control and posted the results here.

Based on this being the first vacuum system control I have tried to troubleshoot I suspect it is the vacuum amplifier.

thanks,
Jim
'85 300D
'95 E320
'97 CRV

I have never replaced an amplifier. I suspect that you have not reproduced the proper oriface size at the source line that broke; remember I told you not to glue it back together. The original hole is either .5 or .6mm. That is a little over 0.020in. If you make the hole bigger the metering system can't control the vacuum.

Have you measured your boost signal? If it isn't getting to the amplifier the vacuum will not be dropped as it grows. If you don't have a boost signal at the amp then you also probably don't have one to the aneroid. Check it out.

ok - road test number 48
 

"teed" into the line from the aneroid to the vacuum amplifier ran the car for a few miles and under load, seemed to level out at around 9 psi, highest I saw was 9.5 psi. Did not seem to want to go any higher - I guess this is an indication that the waste gate is opening. Looks like the boost works. Could the "vent" line that allows it to go to 0"Hg vacuum be plugged? I will test the vacuum pressure again after I have replaced the brake vacuum line check valve (with the "fixed" orifice size). I will not be surprised if that is not some of the problem because of some diyer "cleaning" the line out :)

The car ran good during the whole test.

Jim
'85 300D
'95 E320
'97 CRV

Sorry to bring this thread up again but some people might still find it very useful! like I!!!

I was so bored so I just started troubleshooting my car fixing small bits that came off and polishing things up. I then decided to look at all the vacuum lines associated with the transmission.

All good...

Looked at the bowden cable.. took it off and when popped off it was very tight as in the cable is pulled at idle...so I "loosened" it and made the cup end of the cable right on top of the ball.

Reassembled it.. (thinking it wouldn't make much a difference..) and first thing I noticed the car would start shifting earlier and smoother!!!!!!!!!!!

I couldn't believe it.. drove like a normal car hehehe.. I guess I had been driving my car with a tranny that was out of adjustment!

I then loosened it more.. i might have given it some slack so I'll take the slack off tomorrow to make it perfect...

however I couldn't believe how beautifully it drove...
what an amazing night drive it was!!

Thank thanks thanks !!!! it wouldn't be possible without this wonderful forum!

I was ready to live with it thinking that it's an old car...

I never did figure mine out
 

just bought another one (the 300TD) that shifts perfect :). I am considering connecting the vacuum gauge (on the 300TD) to the line going to the tranny on it and see what kind of numbers I get. The 300D is still in high gear by the time it gets to around 30-40 mph. I've replaced the Bowden cable, checked the vacuum modulator on the side of the tranny and replaced the round "blue" vacuum controller located on the drivers side engine compartment and it still shift early. When I get the 300TD like I want it I will get back on this. Sometimes I wonder if it is actually in the transmission itself.

I thought it should be in high gear at 30-40 mph with very light throttle?

Re: I never did figure mine out
 

[QUOTE]Originally posted by engatwork
[B]just bought another one (the 300TD) that shifts perfect :). I am considering connecting the vacuum gauge (on the 300TD) to the line going to the tranny on it and see what kind of numbers I get.

If that thing is shifting perfectly, then I wouldn't touch it!!:D :D