Does anyone know what the vacuum should be on the 1984 TD ?
I have installed a vacuum gauge and the reading is 14 at idle.

Now when stepping on the gas pedal, the vacuum drops right away to 5 as the engine RPM increases. I would think as the RPM increases, the vacuum should go higher or at least stay the same ?

I am thinking there might be a leak in the vacuum line to the transmission modulator OR the modulator has a vacuum leak ?????
My reason for this thought, is that the vacuum drops off and stays at 5 while driving and returning to 14 when the throttle pedal is let right off ( on coast )
I am sure as the throttle is opened, the little valve on the injection pump allows vacuum to go to the modulator on the transmission. This would be the reason the vacuum rises to 14 at idle when the throttle pedal is let off on coast.

Any idea would be appreciated.
Thanks kindly.

 

It depends on where you plugged the gauge into.

After the VCV ("the little valve on the injection pump"), this is normal, it bleeds off vacuum as you increase rpm.

Utilize a different location to attach your gauge to.

Here is a link to a video of a VCV out of the car:
YouTube - MB VCV operation, part #617 070 02 46.avi

 

I relocated where I tapped the gauge in.

The vacuum goes to 19 in and does not vary with throttle. It does drop if you do repeated braking but returns to 19 after that .
I see it sometimes varies up and down every few seconds from 19 to about 14 or 15 as u drive on the flat road. Not sure of the reason for this any ideas ? High vacuum reading also seem to make for harder shifting through all gears ?

There is a brown restrictor in the vacuum line going to the VCV on the injection pump. What reason is it there ?

Thanks for the link on You Tube .

 

Yes, the transmission needs a lower vacuum, ~15, 14 is fine.

The other consumers usually get ~21-22 inHg.

 

Question regarding the operation or the VCV Valve.
With throttle at idle reading is 14 in. to transmission modulator.

Soon as you move throttle a very small amount and before engine RPM increases the vacuum drops to 5 in. and will stay at this reading unless you go wide open throttle then it drops to 0 in.

Should there not be a gradual drop in vacuum as you give it more throttle and not a quick drop to 5 in. as soon as u touch the throttle.

I am looking for a way to soften the up shifts ?
Down shifts at very smooth and you can not feel them.

Up shifts are alot softer when the engine is cold and also softer under medium or heavy throttle.

Any ideas would be appreciated.

I have two vacuum gauges connected at the moment.
One in the main line from the vacuum pump to the brake booster reading 20-21 in which I feel indicates the vacuum pump to be in good condition ?

The other tee's in at the line to the transmission modulator which reads about 14 or 15 at closed throttle dropping instantly to 5 in at the slightest touch of the throttle and dropping to 0 in at wide open throttle.

 

Can this be tried by removing the lines and blocking them off at the 3/2 valve connection rubber block on top of the valve cover ?

 

Question

In the main vacuum line from the pump to the brake booster there is a valve of some sort that the lines to various vacuum operated devices come off of. Looks kind of like a small funnel with two small vacuum hose connectors. What does this device do any idea ?