The 1979 Chevrolet P30 is a step van with a 6.2-liter engine. The box van is designed for hauling cargo and making deliveries. It has two front seats and a sliding door in the cab for access to the cargo area. The back of the van uses a locking roll-up door for access to the cargo area. Troubleshooting the van requires basic mechanical knowledge and the ability to detect changes in performance.
Attempt to start the vehicle. If the engine does not have the power to start, attach jumper cables to the battery and to a running vehicle. Allow the battery to charge and start the vehicle. If the problem persists, check for an auxiliary battery and a battery isolator. A bad isolator will cause the starting battery to drain.2
If the van does not have an auxiliary battery and the starting battery charges, use a voltage meter to test the alternator. Replace the alternator if it does not supply electric current. The bad alternator will ruin the battery if it is not replaced.3
Attempt to start the vehicle. If the engine cranks but does not fire, replace the spark plugs. If the engine still will not start, the carburetor must be serviced. Spray the carburetor with a commercial cleaner and attempt to start. Have the carburetor fixed if the problem continues.4
Pay attention to the van's performance as you drive. If the van sputters and the engine power surges, the fuel pump may be going bad. If the van is difficult to steer and turn, the power steering pump may require replacement. If it grinds on turns, the U-joints may require replacement.5
Drive at variable speeds to test the transmission. If the van jolts or hesitates while shifting, the transmission must be serviced. The transmission is likely to develop issues over time if the van is used for heavy-duty hauling.