You can't, There is no adjustment. You either have a bad clutch slave cylinder, are worn out clutch parts.
check clutch slave cylinder
The slave cylinder I think you are talking about is the clutch slave. The slave is mounted under the truck. It will be near the bell housing where it can push the clutch fork. Locate your clutch master cylinder and follow the line down to the slave.
YOU CAN'T. The clutch is either worn out are the clutch slave cylinder is bad.
Check your clutch master cylinder and slave cylinder for leaks,if no leaks,then you need a new clutch kit.
check for leaks
The slave cylinder is not on the firewall, it is at the transmission. The master cylinder is on the firewall.
look under your truck at your transmission,its bolted on with 2 bolts atthe rubbercover,check for leaks,if it is about 20 bucks.
Where is the clutch fluid on 1993 nissan pickup truck.
You have to remove the transmission to get to the clutch slave cylinder on that truck. You can pull the engine if you want and get to it. YOUR CHOICE.
It is made on to the clutch slave cylinder that mounts on the side of the transmission.
first take off slave cylinder, it should be mounted on your frame, then take off hoses, connect hoses to new slave cylinder. mount slave cylinder back to frame and bleed ur clutch for f*****g hours.