Mike's Workshop Manuals: Service manuals for every vehicle
Home >> GMC >> 1987 >> Forward Control 7.4 W, Standard >> Repair and Diagnosis >> Transmission >> Automatic Trans >> Overhaul - THM 400 >> Testing >> Vacuum Regulator Valve (Diesel Models Only)

Vacuum Regulator Valve (Diesel Models Only)

  1. Attach vacuum regulator valve to fuel injection pump. Valve body must be securely attached but free to rotate on pump. Attach vacuum source of 9.0-10.4 psi (.6-.7 kg/cm2 ) to bottom vacuum nipple. Attach vacuum gauge to upper nipple.
  2. Insert vacuum regulator gauge bar between gauge boss on injection pump and wide open stop screw on throttle lever. Rotate throttle shaft and hold lever against gauge bar. Slowly rotate vacuum regulator valve body clockwise.
  3. Setting will only be valid if performed with clockwise rotation. When vacuum gauge reads 5.3-5.9 psi (.37-.41 kg/cm2 ), tighten valve body mounting screws. Check setting by releasing throttle lever to idle stop position.
  4. Rotate throttle shaft back until lever rests against gauge bar again. Check vacuum gauge reading and ensure it is still 5.3-5.9 psi (.37-.41 kg/cm2 ). If not to specification, reset valve and check setting again.
scientia non olet · About Mike's Workshop Manuals