On my '87 auto, if I try and pull a vacuum on the lines going to the rear fuel damper, regulator, flappy valve and gearbox by connecting the vacuum pump to the outlet on the splitter where the vacuum line that come from underneath the intake manifold connect

The vacuum splitter - vacuum pump connected to the line by the MAF
- should I get a vacuum?
I tried, and didn't.

 

You're going to have to pump for a long time to get vacuum at that junction because of all of the components attached to it. Especially the transmission lines.

I would test them one by one individually to find any faults as testing them all at once means your either going to detect a leak or not on all of the components and it wont narrow down the issues.

 

^^ Thanks Blake - Make perfect sense. I may have spent to much time under the bonnet when I did this.^^

 

Your flappy vacuum should not be taken from that connector-it should be derived from the passive vacuum reservoir system. I suspect you have the end users confused but...?

The connector at the rear of the manifold supplies dynamic vacuum to the fuel regulator/dampers, the gearbox shift damper and the tank vent device. To test for holding vacuum you must undo the connection from under the inlet manifold and use that to connect the Mityvac to then t should pull a vacuum easily. If you use a spare connector on the multi way thingy you will never pull a vacuum without killing everything on earth!

 

Thanks Fred - You are correct, I confused the feed for the front regulator as going to the flappy.
Unfortunately I found a leak in the gearbox line - so another happy Sunday under the 928

 

Thanks Fred - You are correct, I confused the feed for the front regulator as going to the flappy.

 

Unfortunately I found a leak in the gearbox line -
Really this is fortunate^^^ as now your vacuum system is one leak closer to not leaking,
and restoring the performance that it had from when it was new.

 

That is progress! Now you need to determine whether it is the line that is shot or the diaphragm in the actuator of the shift modulator.