1989 Gmc S15 Low Vacuum And Timing Mark?

[vikasintl]

1989 Gmc s15 pickup 2wd , odometer - 112000 4 cylinder 2.5 liter automatic

 

I checked vacuum is approx. 15 and goes little lower...

 

and when I start its high idle like 1050 rpm and than after a while it calms down

 

I tried to check timing which should 8 btdc...but I can't see timing mark

 

can you guys suggest me how can I find timing mark? I can see 12,8,4,0 marks but noting on pulley..

 

also what could be main reason for low vacuum like 15? and how to trouble shoot?

[hrspwr]

The best way is to get underneath the truck and find the timing mark on the balancer(it will be a groove in the balancer). Once you find it get a paint pen or chalk to mark it a different colour so that you can see it when you check timing. The other thing is that you have to disable the electronic advance in the distributor. There should be a wire with a single connector on it to unplug (think it is a tan wire that is normally out of the loom).