And.... This port seems to supply vacuum ultimately to the air injection pump which is critical to passing smog. So, we need to figure it out. Either we need the right modulator or I need to see where else we can T in to get vacuum to that line...
I see now, in the schematic, the modulator has an extra port "S" where most only have P, Q, and R.. His only has P, Q, and R so it looks like I need to find one with a total of 5 ports.
Actually, a lot of them, like on my 60 have that larger port on the bottom of the modulator. Does that one in the picture have all 4 on the side or does it also have one on the bottom?
Very interesting indeed. I will see what I can learn. My friend had been building this truck for years and when it couldn't pass smog it sat for almost 10 years. It was garaged and is in pristine condition, but if the wrong part was swapped in it's likely that memory was lost to history...
That must be one mysterious port. Is there not someone in the mud community that can post a picture of where it goes and maybe a general picture of that side of the engine bay on a CA 2F smog legal truck?
Frank
Looking at this schematic, that port doesn't show a connection. Also interesting, the schematic doesn't show this port on the air cleaner housing that points to the driver's side above the carb. Not sure what to do with these.
I am helping a friend with his 1979 40 and I can't figure out where this capped off port goes. The diagrams sort disappear into a sea black ink. Any ideas?