It all started out by getting some CELs for the AIR system, and EGR. Codes 327, 328, 332, and I lost the other codes, but I think they were close to 311, or 312.
I began by checking for vacuum at the source (intake vacuum tree). There was good vacuum at the tree, where the main emissions vacuum line connected to the tree, OK, now to the Vacuum reservoir, very low vacuum reading on the output of the vacuum reservoir, and went down fast after engine stopped. So, I took the vacuum reservoir off, and it simply would not hold a vacuum, I believe the seal where the plastic connector fits into the soup-can was not sealing. A new reservoir soup-can was not readily available, so I made one out of 3 inch Schedule 40 PVC pipe, probably not the right solution for everyone, but it is working for me. https://www.ford-trucks.com/g/picture/8930076
Now I had vacuum at my Vacuum Reservoir. So I went to the Vacuum Solenoid location, https://www.ford-trucks.com/g/picture/8930083 rear of rocker cover, driver side. The Vacuum at the supply line there was steady but very low, and would bleed off after the engine was stopped.
So, there was a leak in the main line between the Reservoir and the Solenoids, hidden under the intake plenum, in impossible places to access. I decided to just remove and replace all the old Emissions vacuum lines. I removed the "vacuum harness" from under the intake plenum (what a terrible place to put it, so hot and hidden). I just cut it and removed it. Upon removal of the vacuum harness, I found that the corrugated tubing and main plastic vacuum line had been burnt and melted by the EGR pipe, https://www.ford-trucks.com/g/picture/8922922
So there was my main line leak, and the pink vacuum line from the Solenoids to the AIR Diverter valve was just broken and brittle. https://www.ford-trucks.com/g/picture/8922924
I decided I was not going to "hide" my new vacuum lines on the hot side of the engine, and going around the top end of the head like the old lines did.
I ran a line directly from the vacuum tree to the reservoir, then ran the main line from the reservoir right over the top of the intake plenum to the solenoid area, other vacuum line cross there, so why not?
I had to modify the vacuum tubing at the solenoids a little to accommodate the new routing of the main line, since the new source was coming over the top. be careful not to reverse the function of the little blue check valve. https://www.ford-trucks.com/g/picture/8930083
Then I ran new lines from the TA B and TA D solenoids to the AIR diverter valve in the front of the engine, https://www.ford-trucks.com/g/picture/8930079
Also routed around the tappet cover https://www.ford-trucks.com/g/picture/893
The EGR plastic line was retained because I like the way it looks, and It had no leaks at this time. With this emissions vacuum system restored, the CELs went away for the AIR, and EGR.

Some More Miscellanious Pictures:
Vacuum Tree about Normal >> https://www.ford-trucks.com/g/picture/8930085
Similar, but zoomed out >> https://www.ford-trucks.com/g/picture/8930084
Ford Vacuum Line Diagram >> https://www.ford-trucks.com/g/picture/8930082
Vacuum Canister Cnnections >> https://www.ford-trucks.com/g/picture/8930077
New Vacuum Line Over Plenum >> https://www.ford-trucks.com/g/picture/8930078

 

At the general age of the trucks in this sub-forum, they probably all have some broken plastic vacuum lines. Wouldn't hurt to re-plumb the plastics, that's for sure. I need to do this to mine, once I find a source for the plastic/nylon/??? tubing used in our trucks. That rubber stuff from Auto Zoo tends to split at the ends.

And, what is it with the pink vacuum tubing? Every time I see some of this stuff in the JY, it's all crumbly and turns to dust in your hand.

 

Hey MPZ , liking your topic here. Going to have to redo my entire vacuum system on a 1988 so thanks for documenting your work.
Do you know what line size most of the hose is?
Like your solution to the leaky soup can too.

 

Hi Ray: Yes, the lighter tubing is terrible, the white to my climate control valve just vaporized... I think the black pigment in the plastic/nylon is much better, except where it burns on the EGR tube.
I have not had much trouble with the rubber, but I will keep an eye on this new stuff, good comment to keep in mind. Thank you!

Yellercat: I used two sizes, although probably not perfect, but in a small town, you take what you can get. I used 5/32" to go from the solenoids to the AIR diverter valves in the front of the engine, and to the EGR, (My Green EGR nylon broke since I did the write up) And I used 7/32" for the main line from the manifold tree to the reservoir, and from the reservoir over to the solenoids. There are definitely two sizes in these locations, those worked for me.
Thank you for the comment on the reservoir, it may not be for everyone, but I like it too.

 

MPZ, I've been searching high and low for a detailed post illustrating the vacuum lines on my 88' 4.9. I can now replace damaged and missing vacuum lines. I have already made a trip to my local JY and found a plastic vacuum canister to replace that crappy original can. Thanks so much!

 

thank you for the detailed write up

 

What is the purpose of the soup can (vacuum reservoir)? When I rerouted/relined my vacuum plumbing, I removed this from my system as the previous owner had ripped out most of my secondary air system. Also my 92 5.8 did not appear to have a check valve on the oem harness between the egr solenoid and the vacuum inputs to my solenoids, I will try to double check my spare oem harness I have laying around to confirm it. Again, what is its purpose?