Fuel System Issues (even if fuel is present):
* Fuel Pump Relay: This relay controls the fuel pump. If it's failing intermittently, the pump might cut out while driving, giving the impression of no fuel. This is a common culprit for seemingly random stalling.
* Fuel Pump: The pump itself could be failing, especially given the age of the truck. It might work intermittently under pressure, failing when the engine demands more fuel.
* Clogged Fuel Filter: While you mentioned fuel is present, a partially clogged filter can restrict flow enough to starve the engine under load (acceleration or hills).
* Fuel Pressure Regulator: This regulator maintains consistent fuel pressure. A faulty regulator could cause erratic fuel pressure, leading to stalling. This could also cause fuel to return to the tank, giving the false sense of fuel being present.
* Pick-up tube in fuel tank: The fuel pump's pick-up tube could be clogged or damaged, preventing it from getting fuel from the tank. This is more likely if the truck was low on fuel before the problem occurred.
Ignition and Electrical System Issues:
* Crankshaft Position Sensor (CKP): This sensor tells the engine's computer where the crankshaft is, allowing for proper ignition timing. A faulty CKP will cause the engine to stall.
* Cam Position Sensor (CMP): Similar to the CKP, a bad CMP sensor will disrupt ignition timing.
* Ignition Coil: A failing coil can cause misfires or complete failure of spark to one or more cylinders, leading to a stall.
* Distributor (if equipped): Older vehicles have distributors; a failing distributor cap, rotor, or points can cause intermittent misfires leading to a stall.
* Wiring Harness: Damaged or corroded wiring in the fuel system or ignition system can cause intermittent interruptions.
* Computer (PCM): While less common, the Powertrain Control Module (the truck's computer) could have a fault causing intermittent shutdowns.
Troubleshooting Steps:
1. Check the obvious: Ensure the fuel tank actually has fuel. Don't rely solely on the gauge.
2. Listen for the fuel pump: When you turn the ignition key to the "on" position (before cranking), you should hear the fuel pump prime for a few seconds. If you don't, the pump or relay might be the problem.
3. Inspect the fuel filter: Check for clogging.
4. Check fuel pressure: This requires a fuel pressure gauge and is best done by a mechanic if you're not experienced.
5. Check for error codes: A scan tool can read diagnostic trouble codes (DTCs) stored in the PCM, which can pinpoint the problem.
6. Inspect wiring: Look for damaged or corroded wiring, especially near the fuel pump, ignition components, and sensors.
Recommendation:
Given the complexity of the possible causes, taking your 1993 Silverado to a qualified mechanic is the best course of action. Attempting to diagnose this without proper tools and experience could lead to further damage or incorrect repairs. The intermittent nature of the problem makes it difficult to pinpoint without diagnostic tools.
