Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSGMC1984SUBURBAN C2500, 6.2 J, 400/M40REPAIR AND DIAGNOSIS (SINGLE PAGE)TRANSMISSIONAUTOMATIC TRANSSERVICING - A/TADJUSTMENTSVACUUM REGULATOR VALVEDIAGNOSIS & TESTING
1984 GMC Suburban C2500, 6.2 J, 400/M40
Diagnosis & Testing
1984 GMC Suburban C2500, 6.2 J, 400/M40SECTION Diagnosis & Testing
- Loosely assemble throttle position switch to fuel injection pump with throttle lever in closed position. Attach a continuity meter across terminals (light duty vehicles IGN Pink and EGR Yellow).
- Insert proper "switch-closed" gauge block between gauge boss on injection pump and wide open stop screw on throttle shaft. Rotate and hold throttle lever against gauge block.
- Rotate throttle switch clockwise (facing throttle switch) until continuity pivot occurs (high meter reading) across terminals. Hold switch body at this position and tighten mounting bolts to 4-5 ft. lbs. (5-7 N.m.).NOTE: Switch point must be set only while rotating switch body in clockwise direction.
- Release throttle lever and allow it to return to idle position. Remove "switch-closed" gauge block and insert "switch-open"gauge block. There should be no continuity across terminals.
- In no continuity exists, switch is set properly. However, if there is continuity, then switch mist be reset by returning to step 1) and repeating entire procedure.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.