what are the vac. switches to electrical connections on firewall?

[Swims350]

Willl it even work with that unhooked? seems like I had it unhooked onm the 86 we had and it wouldn't even start, or try to crank over. not sure though.

[VileZambonie]

That is the procedure to set the timing on your truck.

[Swims350]

duh lol my bad I remember reading that in the hayes manual.



Still though guys if I do as they mentioned in that right up does that black plugin get plugged in or do I leave it hanging or cut it off?

[Jim_Hensley]

I know this is old, but I found that 2 wire round plug on my transmission on a 86 van i have and started looking into it and found this thread, but yea , my van with EST says on the emission sticker to just unplug the Vac advance line, st the timing and then plug the line back on the advance, now my advance line has Vac full time as did the line that was supposed to go to the Vac advance on my 84 gmc when i made sure all the vac lines were hooked up according the the Rad support sticker and it also had vall vac at idle, is this normal for it to pull vac at idle?  I know the tip in switch is the one next to the A/C and the lock up is the drivers side firewall one