Symptoms
- Engine turns over noticeably slower than normal
- May eventually catch after a long crank, or not at all
- Worse in cold weather
- Dashboard lights may dim heavily during the attempt
Likely causes
- CommonWeak or aging 12V batteryA battery losing capacity often shows up first as slow cranking.
- CommonCorroded or loose battery terminals/cablesResistance in the connection reduces the current reaching the starter.
- PossibleFailing starter motorWorn internal brushes or windings can cause weak, slow cranking.
- PossibleWrong-weight or very cold engine oil increasing resistanceThick oil makes the engine itself harder to turn over.
- PossibleBad engine-to-body ground strapA poor ground can starve the starter of current even with a good battery.
What to do
- Turn on the headlights and note if they're noticeably dim before you even try to start.
- Check both battery terminals for corrosion or looseness and clean/tighten as needed.
- Try jump-starting the car; if cranking speed improves a lot, the battery is the likely culprit.
- Have the battery and starter draw tested at an auto parts store or shop.
- Check that the engine oil is the correct viscosity for the season, especially in cold weather.
- Inspect the ground strap between the engine and the chassis for corrosion or looseness.
- If the battery tests fine but cranking is still slow, have the starter motor tested or replaced.
- Avoid repeated long cranking attempts, which can further drain a weak battery and heat up the starter.
Tools and parts
- Jumper cables or jump box
- Wire brush
- Multimeter (optional)
Group-size car batterySearch: “car battery group size for [year make model]”
Starter motorSearch: “starter motor for [year make model]”
When to call a pro
If cleaning terminals and a jump don't restore normal cranking speed, have a shop test the starter and battery together to identify which is failing.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.