How to Fix a Car That Jumped Time (Signs, Damage, Repair)

A car that has “jumped time” has a timing belt that slipped on its toothed pulley or a chain that stretched, so the camshaft no longer turns in step with the crankshaft. Per GMB, a belt can snap or stretch enough to slip, and a slipped belt throws the timing off. This guide covers the signs, the interference-engine damage risk, what a shop does, and how a compression test fits in.

What Does It Mean for a Car to “Jump Time”?

GMB explains that the timing belt keeps the crankshaft and camshaft in sync: the crankshaft is turned by the pistons, and the camshaft opens and closes the valves. When the two stay in step, the valves open and close in sequence and the engine produces power as it should. “Jumping time” is the everyday phrase for that step being lost. GMB describes two ways an old belt can fail: it can snap, or it can stretch enough to slip on a toothed pulley. If it snaps, the engine will not run and there may be severe damage. If it slips, the timing is thrown off.

Chain engines can lose their timing too. GM’s service bulletin 12-06-01-009F (March 2015) deals with stretched timing chains on its 3.6L High Feature V6, where a stretched chain sets cam and crank timing trouble codes.

Why Does a Car Jump Time? Common Causes

The makers’ pages point to the parts around the belt as often as the belt itself. Dayco’s timing component guide says one of the most common causes of timing belt failure is worn tensioner or idler pulleys, and GMB’s diagnosis page warns that if a failed component is not found, the next belt will fail too. The causes named in those two sources are:

• Worn tensioner or idler pulleys. Dayco lists these as one of the most common causes of belt failure. It also says loss of belt tension may lead to major engine damage.
• Loose or low belt tension. Dayco’s wear chart ties loose teeth to low working tension, loss of tension in the belt, and foreign material in the drive.
• Leaking seals or a leaking water pump. Dayco says leaking or worn cam and crank seals contaminate the belt and cause premature failure, and that coolant from a worn leaking water pump can contaminate and destroy a new belt. GMB lists the cam seals and crank seals among the parts to check.
• Improper installation. Dayco’s wear chart lists improper installation among causes of belt wear and noise.
• Missed replacement interval. Dayco says manufacturers publish OE replacement intervals and that they are in the owner’s manual. It adds that these intervals vary widely by make and model.
• A stretched chain (GM 3.6L V6). GM’s bulletin covers a stretched chain that sets codes P0008, P0009, P0016, P0017, P0018 or P0019.

Dayco also says timing belts break most often at engine startup and shutdown, when the maximum amount of tension is placed on the belt. For the service interval on one popular model, see our guide to the Honda CR-V timing belt or chain, and for which cars use a belt at all, see do all cars have timing belts.

Symptoms of a Car That Jumped Time

The table lists what the makers’ pages name, with the source beside each line. No page ranks these by how often they occur, and GMB notes that most often a belt gives no symptoms and simply breaks one day.

Symptom	What the source says	Source
Sluggish or no acceleration	Listed as a symptom of a slipped belt	GMB diagnosis page
Hard starting, sometimes after stopping the car	Listed as a symptom of a slipped belt	GMB diagnosis page
Stalling or a shaking engine	Listed as symptoms of a slipped belt	GMB diagnosis page
Squeaking, rough idle or misfire, power loss	Listed as signs a belt is going bad	GMB, “what if the timing belt breaks”
Engine stops and will not restart	What happens when the belt snaps; a new belt (and damage repair) is needed first	GMB, “what if the timing belt breaks”
Trouble codes P0008, P0009, P0016 to P0019	Set by a stretched timing chain on the 3.6L High Feature V6 (2007-2012 models in the bulletin)	GM bulletin 12-06-01-009F

Jumped Time or a Starter Problem?

The maker pages do not give a test that separates the two. What Innova does give is a starting condition for a meaningful compression check: Innova’s tester manual says the battery must be fully charged and the starter system in good condition before testing. A car whose symptoms match the slipped-belt list above needs a shop to look at the timing drive.

Is Your Engine an “Interference” or “Non-Interference” Type?

This is the fact that decides how bad a jump can be. Dayco defines an interference engine as one where the pistons and valves share the same space in the cylinder but move at different times, so one or more valves may open into the area where the piston travels. In a non-interference engine, an open valve never enters the area the piston travels in. GMB says interference designs allow higher compression ratios, which gives more power and better fuel efficiency, and states that almost all modern engines have an interference design.

	Interference engine	Non-interference engine
Piston and valve paths	Share space; a valve may open into the piston area (Dayco)	An open valve never enters the piston area (Dayco)
If the belt breaks	Piston can contact valve; damage can be severe (Dayco)	Engine stops, no damage, but it will not run until the belt is replaced (Dayco, GMB)
Damage GMB lists	Bent or broken valves, cylinder head, camshaft, cylinder wall and piston damage	None expected
What sets the damage level	Dayco says it varies with engine speed at the time of failure	Not applicable

Neither maker lists engines by type, so the answer for your car comes from the service information for that exact engine. Dayco and GMB describe the damage in terms of a broken belt, and neither publishes a tolerance for a slip of a few teeth.

How to Fix a Car That Jumped Time

Valve timing is set with the marks and tools in the service manual for that exact engine. This page does not give a generic “line up the marks” routine, and it does not give mark positions or torque values, because they differ by engine and a wrong set can bend valves. GM’s own bulletin states that its bulletins are for professional technicians, not do-it-yourselfers.

What a shop does, per the maker’s installation tips

Dayco’s installation tips for a belt job give a sense of the work involved:

• Line up the engine timing marks at zero and mark them with paint after the timing cover is removed, including the cam and crank sprockets.
• Lock the cam sprockets in place with a tool. Dayco’s Camlock tool page says that when a belt is removed the engine can be susceptible to cam sprocket spring back, which can cause expensive valve damage when valves contact the piston.
• Follow the OE instructions for installing and setting the tensioner. Dayco says to rotate the engine 3 to 4 times afterward to recheck belt tension and timing mark alignment.
• Use a torque wrench where needed, and a crank holding tool when reinstalling the harmonic balancer.
• Replace the tensioner, idler pulleys and, where the belt drives it, the water pump. Dayco says manufacturers recommend replacing the timing components with the belt.

Hydraulic tensioners are another reason this is not a casual job. Dayco says the lock pin holds the arm in position and is removed just after installation, and that a reused hydraulic tensioner must be compressed very slowly in a bench vise and pinned before it goes on.

Chain engines: the GM 3.6L V6 example

For stretched chains on the 3.6L High Feature V6, GM’s bulletin says its service kits do not contain the idler sprockets, camshaft actuator gears, crankshaft driven gear or chain guides, because those parts should not be replaced for a stretched chain that sets the cam-crank codes. It says guides should be replaced only where the wear block surface is worn down into the base friction material. Other engines have their own procedures.

If the engine is damaged

When a belt or chain failure has let pistons and valves meet, GMB’s list of possible damage is bent or broken valves, cylinder head damage, camshaft damage, cylinder wall damage and piston damage. A shop decides after inspection whether the repair is a timing job alone or a cylinder head job. Neither GMB nor Dayco publishes a cost for either.

Compression Test and Other Checks

A compression check is the basic diagnostic described in tester makers’ manuals. Innova says it can help identify worn or damaged pistons, rings, valves and gaskets by measuring cylinder pressure at cranking speed. Neither Innova’s nor OTC’s manual mentions timing belts; the test measures cylinder pressure. The steps below are summarized from the Innova 3612/3614 manual and OTC’s 5606 label, and the engine’s own service manual comes first where it differs.

• Safety first: Innova says to wear eye protection, put the transmission in park or neutral, set the parking brake, block the drive wheels and disable the ignition system so the car cannot start. It also warns that engine parts will be hot.
• Battery fully charged and engine warm, per Innova; OTC also says to run the engine to operating temperature first.
• Remove all spark plugs, hand-tighten the tester hose only, and crank at least five compression strokes (OTC adds: or until the reading stops rising), the same number for every cylinder.
• Do not use a long-reach adapter in a short-reach hole. Both makers warn it can hit the top of the piston and damage the engine.
• Return the throttle plate to its closed position before starting. Both makers warn that failing to do so can cause serious engine damage.

Reading the result: Innova calls compression normal if the lowest cylinder is at least 75% of the highest. Its own example is 140 psi highest, so the lowest allowed is 105 psi (140 x 0.75, arithmetic from Innova’s example). OTC instead says readings should be within the vehicle maker’s specification and not vary more than 10% from cylinder to cylinder, so check the service manual spec for your engine. If a cylinder is low, Innova and OTC both describe adding about a tablespoon (Innova) or a teaspoon (OTC) of oil and retesting: if readings rise, rings are indicated, and if they stay the same, valves may be the cause. Two adjacent cylinders 20 psi or more below the rest point to a head gasket problem. For tester options, see our guide to affordable engine compression testers.

Related reading: engine noises when turning on and off and what to check first on a car problem.

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Frequently Asked Questions (FAQ)

How much does it cost to fix a car that jumped time?

A jumped-time repair has no single price. GMB says timing belt failure can lead to thousands of dollars in engine repairs. The cost depends on whether valves, pistons or the cylinder head were damaged, which only an inspection shows. Ask a shop for a written estimate for your exact engine.

How long does it take to fix a car that jumped time?

There is no one time for every engine. As one documented example, GM’s bulletin 12-06-01-009F lists warranty labor times for installing a timing chain kit on its 3.6L V6 models from 5.3 hours to 9.7 hours, depending on the model and drive type. That is the kit installation only, on those engines, and it does not include repairing any valve or piston damage. Dayco adds that if a technician has to open the timing drive more than once, labor can more than double.

Will a car start if it jumped time?

It may or may not. GMB lists difficulty starting, sometimes after stopping the car, stalling and a shaking engine as symptoms of a slipped belt. For a belt that has broken, GMB says there is no way to start the engine again until a new belt is installed and any engine damage is fixed. If a car cranks but will not start, a shop has to check the timing drive.

What are the main symptoms of a jumped timing belt or chain?

For a slipped belt, GMB lists sluggish or no acceleration, difficulty starting, a stalling engine and a shaking engine. On the stretched-chain engines covered by GM bulletin 12-06-01-009F, the symptom is stored trouble codes P0008, P0009, P0016, P0017, P0018 or P0019.

Is it safe to keep driving if the timing belt or chain jumped?

No maker publishes a safe distance or a safe number of start attempts. Dayco says that when a belt breaks on an interference engine and a piston contacts a valve, the engine can be severely damaged. GMB’s advice for a belt that breaks on the road is to coast to a safe spot and call a tow truck. If you suspect jumped timing, have the car inspected before driving or cranking it again.

How can I tell if my engine is an interference or non-interference type?

Dayco and GMB describe the two designs but do not list which engines are which. Dayco defines an interference engine as one where an open valve can enter the area the piston travels in. The answer is specific to the exact engine, so check the service information for your vehicle or ask a shop that can look it up by VIN.

Sources and Scope

Facts above come from GMB North America, “Why It Is Critical To Replace Your Timing Belt Kit Before It Fails”, GMB’s “How To Diagnose Belt And Timing Component Failures” page, Dayco’s Timing Belt Components guide, Dayco’s Timing Gear Clamp page, GM service bulletin 12-06-01-009F (NHTSA copy), and the Innova 3612/3614 and OTC 5606 compression tester instructions. This guide does not cover repair prices; ask a shop for an estimate.