When a car has "jumped time," it means the synchronization between the engine's crankshaft and camshaft has been lost. The crankshaft controls the pistons moving up and down, while the camshaft controls the opening and closing of the valves. This synchronization is critical and is maintained by a timing belt or chain. If this belt slips, stretches, or breaks, or if the tensioner fails, the camshaft stops turning in sync with the crankshaft. The immediate consequence is that the engine will run very poorly—if it runs at all—and can lead to catastrophic internal damage, especially in interference engines where the pistons and valves occupy the same space and can collide.
The most common symptom is the engine cranking but refusing to start. You might also hear a clattering or knocking sound from the engine bay. If the car jumps time while driving, you'll experience a sudden loss of power and the engine will stall.
The severity of the damage depends entirely on your engine type. In a non-interference engine, the pistons and valves never occupy the same space, so jumping time might only require a new timing belt and a re-synchronization of the timing marks. However, in an interference engine, which is common in most modern vehicles for efficiency, the pistons will smash into the valves that are open at the wrong time. This bends valves, damages pistons, and can break the camshaft, leading to a repair bill that often exceeds the car's value.
| Engine Type | Probability of Severe Damage | Typical Repair Scope | Estimated Repair Cost (USD) |
|---|
| Interference Engine | Very High | Valve job, possible piston/head replacement | $2,000 - $6,000+ |
| Non-Interference Engine | Low | Timing belt/chain replacement, reset timing | $500 - $1,500 |
| Unknown (Common Scenario) | Assume High | Diagnosis, then full assessment | $300 (diag) + variable |
If you suspect your car has jumped time, do not attempt to restart the engine. The first and most important step is to have it towed to a trusted mechanic. They will perform a compression test and visual inspection to determine the extent of the damage. Prevention is key: adhere strictly to your vehicle's manufacturer-recommended timing belt replacement interval, typically between 60,000 and 100,000 miles.
