Possible Cause And Correction
- Check for water contaminated fuel.
- Check fuel pressure, see CHART A6 - FUEL SYSTEM PRESSURE TEST chart in the TBI TESTS/CODES article in this section.
- Check TPS for sticking or binding.
- Check EGR operation. See EGR SYSTEM CHECK chart chart in the TBI TESTS/CODES article in this section.
- On Astro, Safari, and "S" Series trucks, check fuel pump relay; connect test lamp between pump test terminal and ground. Test lamp should be on for 2 seconds following ignition on. On 7.4L engines and some 5.0L engines, the fuel module circuit activates the fuel pump for 20 seconds after ignition is turned on. If circuit is not functioning, a hot, hard start condition may result.
- Check for faulty in-tank fuel pump check valve that would allow fuel to drain back into tank:
- With ignition off, disconnect fuel line at filter.
- Remove fuel tank filler cap and connect radiator test pump to line. Apply 15 psi (1.05 kg/cm2 ) pressure. If pressure holds for 60 seconds, check valve is okay.
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.
- 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/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.