* Short to ground in the wiring: This is the most probable cause. Wires can chafe against the chassis, engine block, or other metal components, especially in older vehicles. Look closely at the wiring harness running from the fuel pump to the fuse box. Pay special attention to areas where the wiring might rub against sharp edges or moving parts. Check for any signs of damage, fraying, or exposed wires. The short could also be within the connector at either end of the wiring harness.
* Faulty fuel pump: A failing fuel pump can draw excessive current, blowing the fuse. While less common than a wiring problem causing the immediate fuse blow, a failing pump often leads to overheating and eventually a short to ground. This wouldn't necessarily be *visible* damage on the pump itself, but its internal workings could be the root cause.
* Short in the fuel pump relay (if applicable): Some systems use a relay to switch the power to the fuel pump. A faulty relay could cause a short. Test the relay with a multimeter if possible. (If it doesn't click when you engage the ignition, it's likely bad. But you should check for power to it too, as it's downstream of the fuse.)
* Wiring harness connector issues: Corrosion or loose connections within the connectors at either end of the fuel pump wiring harness can create high resistance and lead to excessive current draw, blowing the fuse. Clean and inspect these connectors carefully.
* Fuel pump inertia switch (if equipped): Some vehicles have an inertia switch designed to cut power to the fuel pump in a collision. This could be tripped, falsely cutting power. Check the switch and reset it if necessary.
* Incorrect fuse: While less likely, ensure you're using the correct amperage fuse. Using a fuse with a lower amperage rating will blow more readily.
Troubleshooting steps:
1. Visual Inspection: Carefully examine the entire fuel pump wiring harness, from the fuse box to the fuel pump, looking for any signs of damage, chafing, or corrosion.
2. Connector Inspection: Carefully inspect and clean all connectors in the circuit. Use electrical contact cleaner.
3. Multimeter Test: Use a multimeter to check for shorts in the wiring harness. Disconnect the fuel pump connector at the tank, then check for continuity (resistance) to ground. You should measure infinite resistance (open circuit). If you get a low resistance reading, you've found a short to ground.
4. Relay Test (if applicable): Test the fuel pump relay as mentioned above.
5. Inertia Switch Check (if applicable): Check and reset the inertia switch if present.
6. Fuel Pump Testing: While testing the pump itself requires more advanced tools and procedures, if the above steps yield nothing and you have a spare pump, it might be prudent to install it temporarily to determine if the pump is the culprit.
If you're not comfortable working with electricity, it's best to take your S-10 to a qualified mechanic. Working with car electrical systems can be dangerous if not done correctly.
