Symptoms
- Stalling or hard restarting after driving in very hot weather
- Happens more after a short stop with the engine still hot
- Engine cranks but doesn't catch, or catches roughly
- Symptoms often go away once the engine and fuel lines cool down
Likely causes
- CommonFuel vaporizing in the lines from engine heatIn very hot conditions, especially with fuel lines routed near the engine, fuel can boil before reaching the injectors or carburetor.
- PossibleFuel lines routed too close to heat sourcesAftermarket work or aging insulation can worsen heat exposure to fuel lines.
- PossibleWeak fuel pump unable to maintain pressure when hotA marginal pump is more likely to allow vapor lock under stress.
- Less commonOlder carbureted fuel systemVapor lock is more common on older carbureted vehicles than modern fuel-injected ones.
What to do
- If it stalls in hot weather and won't restart, let it sit for 10–20 minutes to let the fuel lines cool and the vapor condense back to liquid.
- Try to park in shade rather than direct sun while waiting, if possible.
- Once it restarts, avoid immediately stopping and restarting in extreme heat if you can help it.
- If this happens repeatedly, have a shop inspect fuel line routing and insulation.
- Have the fuel pump tested, since a healthy pump resists vapor lock better than a weak one.
- Consider a fuel line heat shield if this is a recurring, known issue on your specific vehicle.
Tools and parts
Fuel line heat shield/insulationSearch: “fuel line heat shield”
When to call a pro
If this happens more than once, have a shop check fuel line routing and pump condition rather than just waiting it out each time.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.