You replaced that fraying, squealing serpentine belt expecting smooth running. But now the engine won’t turn over at all – what gives?
A no-start condition after installing a new serpentine belt is often due to simple mistakes made during the repair. With some troubleshooting, you can get the engine firing again.
This article explores the common reasons an engine fails to start after a new serpentine belt is installed. Follow along for tips on diagnosing the specific cause in your vehicle and making the appropriate repairs.
Table of Contents
- Key Reasons the Engine Won’t Start After a Belt Change
- Step-By-Step Diagnosis to Find the No-Start Cause
- Adjusting Serpentine Belt Tension for a Proper Install
- Re-Routing a Misaligned Serpentine Belt
- Replacing a Seized Pulley Bearing Causing No-Start
- Professional Assistance Diagnosing No-Start Issues
- Preventing Future No-Starts After Belt Changes
Key Reasons the Engine Won’t Start After a Belt Change
Here are the most likely causes for a continued no-start problem after changing the serpentine belt:
1. Loose Belt Tension
If the new belt is not tensioned properly per factory specs, it can slip on the pulleys and fail to spin the accessories.
2. Mis-Routed Belt
The belt must follow the correct pulley routing diagram. A reversed or twisted belt won’t drive components properly.
3. Faulty Pulley Bearings
A seized or frozen pulley bearing won’t allow accessories like the alternator to turn freely, potentially causing a no-start.
4. Damaged Sensors/Wiring
Misfiring sensors like the crankshaft position sensor due to rough handling during the job can prevent starting.
5. Low Battery Charge
An accessory drive running while disconnected may have drained the battery below the voltage needed to crank the starter.
In most cases, a basic installation or routing error is the culprit for continued starting issues after changing the serpentine belt. Let’s explore how to diagnose and fix the problem.
Step-By-Step Diagnosis to Find the No-Start Cause
To identify why your engine continues to not start after the new belt install, methodically check:
1. Inspect Belt Tension
Verify the belt deflection by pressing on the longest span while rotated. It should have just 1/2 to 3/4 inch of give when properly tensioned.
2. Confirm Proper Belt Routing
Visually follow the new belt path checking for any crossed up pulleys or backwards loops. Compare to the routing diagram in your vehicle repair manual.
3. Check Pulley Bearings
Try spinning each pulley by hand to feel for rough spots from a bad bearing. Replace any that are seized or lock up rather than turn freely.
4. Reconnect Sensors and Harnesses
Make sure all engine bay wiring connectors like crankshaft position sensors are plugged in properly after any disturbed during service.
5. Charge or Jump the Battery
Use a multimeter to check battery voltage. If low, charge it or jump start the vehicle and try starting again.
By methodically testing these areas, you can zero in on what needs correction to get your engine firing properly again.
Adjusting Serpentine Belt Tension for a Proper Install
If the new belt is loose on the pulleys due to improper tensioning:
- Loosen the tensioner pulley bolt and allow it to rotate into the proper position against the belt.
- Check the torque on the tensioner once the belt is snug according to factory specifications, usually around 30-40 ft-lbs.
- Confirm the belt has just a slight 1/2 inch give on the longest span between pulleys when pressed.
- Avoid over-tightening which strains components. But also avoid loose belts which slip and fail to turn accessories.
Getting belt tension within the right spec prevents premature failure and keeps your accessories spinning.
Re-Routing a Misaligned Serpentine Belt
If the new belt is routed incorrectly:
- Remove it and visually trace the proper belt path per the routing diagram for your specific engine.
- Note the location of idler and tensioner pulleys which commonly get reversed.
- Check that the belt does not ride on any ribbed or grooved surfaces, only smooth pulley faces.
- Set the tensioner pulley to its loosest setting until the belt is routed properly, then apply tension.
Taking time to route the serpentine belt correctly the first time prevents wasted efforts and extra belt wear from misalignment.
Replacing a Seized Pulley Bearing Causing No-Start
To resolve a seized pulley bearing:
- Locate which pulley is not spinning freely by testing each one while rotated by hand.
- Remove the accessory drive belt first to prevent damage during removal.
- Take out the faulty pulley and press out the old bearing, replacing it with a new matched bearing.
- Lubricate the new bearing at install to prevent premature seizure.
- Reinstall the pulley and route the serpentine belt correctly.
Repairing that frozen bearing removes the mechanical resistance preventing a smooth engine start.
Professional Assistance Diagnosing No-Start Issues
If you’ve made the above repairs and the engine still won’t start, have a professional technician troubleshoot further:
- They can test for underlying electrical faults like bad ignition coils or crankshaft position sensor issues.
- Dealership computer scanners can read manufacturer codes pointing to no-start causes.
- Hands-on diagnosis may reveal additional damaged belts, pulleys or accessories.
- Mechanical issues like low compression or timing chain faults are internally out of DIY reach.
Seeking professional help can determine if there is a deeper problem beyond just the serpentine belt replacement that requires repair by a certified mechanic. Don’t continue cranking endlessly on a still non-starting engine.
Preventing Future No-Starts After Belt Changes
Here are some tips to avoid a repeat no-start situation next time you change the serpentine belt:
- Follow the procedure exactly per the repair manual to assure proper routing and tension.
- Clean pulley surfaces thoroughly to prevent belt slippage on oil residue.
- Confirm the replacement belt has the matching length and profile for your accessory drive.
- Inspect pulleys and bearings at each belt change – replace any that are seized or damaged.
- Protect disconnected sensors during service and make sure all are reconnected firmly.
- Disconnect the battery before starting to avoid accessory draining when not spinning.
- Consider having a shop tackle the belt replacement if the procedure seems beyond your mechanical skills.
Staying meticulous during the entire process minimizes oversights that can lead to problems starting the engine again after a belt change.
While the serpentine belt itself rarely causes a no-start condition after replacement, installation mistakes like incorrect tensioning, routing or seized pulleys usually are the causes. Methodically troubleshooting the accessory drive components and making any necessary repairs will have your engine firing properly again. Seek professional assistance if needed to get to the bottom of ongoing starting difficulties.