All:

Think of this as an educational thread that will benefit people who have little knowledge and no one to ask for help (like me).

Last night I was looking at the sensors near my MAP sensor and wondering what exactly they do and what might happen if they crap out. (I have no life). Are these wires or vacuum lines or a mix of both? How hard is it to un-clip those sensors?
If one wire or line goes bad is it as simple as unplugging the clip and swapping out the line/wire/vacuum line? Do you ever "clean" the connectors on occasion with that electrical connector spray cleaner - or is it "if it aint broke, don't fix it"?

Even though this engine is simple as compared to today's engines - I still am trying to get a big picture of what some of these parts are, what they do and how they play together. I am eager to learn everything about the truck, the engine, etc, and this is the place to come.

Thanks and have a great weekend everyone.


Who left rainbow spaghetti in my truck?

 

I don't see any vacuum lines in your pic (except for the large ones with a zip tie fastened around them), only wires. The red and black receptacles are the EEC IV ports. I'm not sure what the other wires are, but it wouldn't hurt to spray them with electronic cleaner and use a toothbrush to clean them up a bit. I would be hesitant to remove the terminals though. They might get damaged in the process.

 

The vacuum lines are there, they are on the bottom and go into that large split loom. All these gizmos are vacuum valves. They are shown on the diagram on the radiator support, positionally correct and labeled in the diagram.

Usually at least two are for smog pump control. Usually two are for EGR valve control. The computer sends signals to the wires on top, and that activates the valves and lets them block or pass vacuum through the colored vacuum lines.

Depending on engine conditions, the computer will direct the air pump air to the cat converter, the cylinder heads, or exhaust to the atmosphere.

Depending on engine conditions, the computer will open or close the EGR valve. One of them sends vacuum to the valve to open it, the other valve is a exhaust valve to vent the vacuum out and close the valve.

 

#1 – Air Bypass Solenoid (TAB)(W/R wire)
#2 – Air Diverter Solenoid (TAD)(W/B wire)
#3 – EGR Control Solenoid (Y wire)
#4 – EGR Vent Solenoid (DG wire)
You can compare your wiring colors on page 60, with the link Chris provided .
Electronic Engine Control - Gary's Garagemahal (the Bullnose bible)

If you start digging around in there, be careful, the vacuum connections to the solenoid valves are very fragile.

Here are photos someone posted previously that shows the vacuum lines buried underneath the wires leading to the connectors.
You can see the 2 mounting studs on the bottom, these are accessible from the under fender skirt above the tire.

In the second photo you can see where the solenoid valves are attached to the fender bracket.
You would want to remove the white vacuum manifold from all three Valves before you attempt to remove a valve assembly from the fender bracket or you may damage the vacuum manifold (3rd photo attached).

The solenoid valves themselves have plastic ports (photo #4), these are very fragile as well, so spraying some penetrate on all this mess might be in order before attempting disassembly.
I guess you get where I say all this old plastic breaks easily.

The last photo is the Vacuum Routing diagram that Dave F was referring to if your truck no longer has its.

 

VJsimone,

Thanks for your reply. These photos really help someone like me to learns best by seeing and doing rather than reading a manual. This is very informative. I will print this out and keep this thread in my notebooks.

Thanks again!