Check Ignition System For:

Proper output signal.
Worn distributor shaft.
Bare and/or shorted wires.
Pick-up coil resistance and connections.
Loose ignition coil ground.
Moisture in distributor cap (where applicable).
Remove spark plugs. Check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Repair or replace as necessary.
If engine starts but then immediately stalls, open distributor by-pass line. If engine then starts and runs, replace distributor pick-up coil.
If hard start occurs with engine at normal operating temperature, see CRANK SIGNAL DIAGNOSIS chart in the TBI TESTS W/ CODES article in this section.
Check fuel pump cycle system on 8500-10,000 GVW vehicles with 5.7L and 7.4L engines.
Check EST circuit No. 423 for short to ground.