Hard Starting (Hot Or Cold)

Check fuel for water contamination. Check fuel pressure. See FUEL SYSTEM PRESSURE TEST . Check TPS for sticking or binding. Check EGR valve operation. See appropriate EGR SYSTEM CHECK chart in GENERAL MOTORS COMPUTER COMMAND CONTROL article in COMPUTERIZED ENGINE CONTROLS section.
On Astro, Safari and "S" series trucks, check fuel pump relay by connecting test light between pump test terminal and ground. Test light should be on for 2 seconds after turning ignition on.
NOTE:
On 7.4L engine and some 5.7L engines, a fuel module circuit will activate fuel pump for 20 seconds after turning ignition
1. A hard start condition may be caused if this circuit is not functioning.
Check for faulty fuel pump check valve. To check for this condition, turn ignition off. Disconnect fuel line at fuel filter. Remove fuel tank filler cap. Connect radiator test pump to fuel line and apply 15 psi (1.1 kg/cm² ). If pressure is held for 60 seconds, check valve is okay.
Check ignition system. If engine starts but then immediately stalls, open distributor by-pass line. If engine then starts and runs okay, replace distributor pick-up coil.
If engine hard start occurs with engine at normal operating temperature, check crank signal. See CRANK SIGNAL DIAGNOSIS chart in GENERAL MOTORS COMPUTER COMMAND CONTROL article in COMPUTERIZED ENGINE CONTROLS section.
On vehicles between 8500-10,000 GVW ratings (5.7L and 7.4L engines), check fuel pump cycle system.