Symptom
Engine turns over slowly
The starter drags the engine round more slowly than usual — a laboured whirring rather than a brisk spin — and the engine may or may not eventually fire. Nearly always a supply problem rather than a starter one, and the two cheap checks come first: battery terminals that look fine can still be poor, because corrosion forms under the clamp where nobody sees it, and the earth strap between engine and body carries the whole starting current back. Note whether it is worse cold, which points at the battery, or worse hot, which points at the starter itself.
Also described as: slow cranking, engine cranks slowly, turns over slowly, sluggish starter, labouring when starting, struggles to turn over, استارت کند میزند, موتور کند میچرخد, استارت سنگین است, arranca muy lento, motor gira despacio, da vueltas lentas, motor de arranque flojo, المارش يلف ببطء, تدور بتقل, الدوران ضعيف وبطيء
What this usually means
A slow crank is a supply problem far more often than a starter problem, and the two cheap checks come before any part is considered. Corrosion forms under the battery clamp, where it cannot be seen, so a terminal that looks perfect can still be a poor joint. And the earth strap between engine and body carries the whole starting current back to the battery — several hundred amps through a braid whose body end sits where road salt collects.
Measure the drop rather than inspecting the joint, because a resting continuity check passes a joint that fails under load: a meter's own test current is milliamps, and the fault only appears at cranking current. German workshop references put the threshold at more than about 0.5 V along the starter cable as evidence of corrosion or a bad connection, taken during the attempt, and the earth path deserves the same test as the positive one.
Whether it is worse cold or worse hot separates the two remaining causes. Cold is the battery: capacity falls sharply with temperature while the oil thickens and the engine gets harder to turn, so a battery that is merely tired copes all summer and fails in the first frost. Hot is the starter: windings and a heat-soaked motor draw more current for less torque, which is why a car parked after a long run cranks worse than the same car in the morning.
The last population is genuine mechanical drag — oil far too thick for the temperature, a seizing ancillary loading the belt, or an engine with a real internal problem. That is rare compared with the first three, and it should be the conclusion after they are excluded rather than the first suspicion.
Working through it
| What you find | Likely cause | How to confirm it | What fixes it |
|---|---|---|---|
| Voltage at the battery posts collapses well below about 9.6 V while cranking | The battery cannot deliver cranking current — capacity or health has gone | Charge fully first, rest, then load or conductance test against the rating on the label. A battery that reads 12.6 V at rest can still fail this. | Renew to the correct type and capacity, and register it where the car has energy management. |
| Battery holds up well but the starter still drags | A high-resistance connection between battery and starter, or a corroded earth strap | Measure voltage drop end to end during cranking, positive side and earth side separately. Above roughly 0.5 V on either is the fault, and it will not show at rest. | Clean and remake the joints, or renew the cable or strap. Re-measure to prove the drop has gone rather than assuming. |
| Worse in cold weather, fine once warm | Battery capacity falling with temperature while thick oil makes the engine harder to turn — a tired battery exposed rather than a new fault | Conductance test cold, and check the oil grade against the handbook for the climate. Compare cranking speed cold and warm on the same day. | Renew the battery, and correct the oil grade if it is heavier than specified. |
| Worse when hot, brisk from cold | Heat soak in the starter — more current drawn for less torque, typically on a starter sited near the exhaust | Measure cranking current and voltage drop with the engine at temperature. A cold measurement proves nothing about this fault. | Renew or overhaul the starter, and refit any missing heat shield — its absence is often why the fault appeared. |
| Cranking current far above the manufacturer's figure with a good battery | Mechanical drag — oil too thick, a seizing ancillary on the belt, or an internal engine problem | Remove the auxiliary belt and re-test: a crank that becomes normal names the ancillary. If it does not, the drag is inside the engine. | Renew the seizing ancillary, or correct the oil. Internal drag needs its own diagnosis and is the least likely of the five. |
| Slow cranking that appeared after a battery or starter was fitted | A joint not properly remade, or a battery of lower specification than the car needs | Compare the fitted battery's capacity and cold-cranking rating against the handbook, and re-torque every connection that was disturbed. | Remake the joints; fit a battery of the specified rating. An undersized battery cranks slowly from the day it goes in. |
-
Voltage at the battery posts collapses well below about 9.6 V while cranking
- Likely cause
- The battery cannot deliver cranking current — capacity or health has gone
- How to confirm it
- Charge fully first, rest, then load or conductance test against the rating on the label. A battery that reads 12.6 V at rest can still fail this.
- What fixes it
- Renew to the correct type and capacity, and register it where the car has energy management.
-
Battery holds up well but the starter still drags
- Likely cause
- A high-resistance connection between battery and starter, or a corroded earth strap
- How to confirm it
- Measure voltage drop end to end during cranking, positive side and earth side separately. Above roughly 0.5 V on either is the fault, and it will not show at rest.
- What fixes it
- Clean and remake the joints, or renew the cable or strap. Re-measure to prove the drop has gone rather than assuming.
-
Worse in cold weather, fine once warm
- Likely cause
- Battery capacity falling with temperature while thick oil makes the engine harder to turn — a tired battery exposed rather than a new fault
- How to confirm it
- Conductance test cold, and check the oil grade against the handbook for the climate. Compare cranking speed cold and warm on the same day.
- What fixes it
- Renew the battery, and correct the oil grade if it is heavier than specified.
-
Worse when hot, brisk from cold
- Likely cause
- Heat soak in the starter — more current drawn for less torque, typically on a starter sited near the exhaust
- How to confirm it
- Measure cranking current and voltage drop with the engine at temperature. A cold measurement proves nothing about this fault.
- What fixes it
- Renew or overhaul the starter, and refit any missing heat shield — its absence is often why the fault appeared.
-
Cranking current far above the manufacturer's figure with a good battery
- Likely cause
- Mechanical drag — oil too thick, a seizing ancillary on the belt, or an internal engine problem
- How to confirm it
- Remove the auxiliary belt and re-test: a crank that becomes normal names the ancillary. If it does not, the drag is inside the engine.
- What fixes it
- Renew the seizing ancillary, or correct the oil. Internal drag needs its own diagnosis and is the least likely of the five.
-
Slow cranking that appeared after a battery or starter was fitted
- Likely cause
- A joint not properly remade, or a battery of lower specification than the car needs
- How to confirm it
- Compare the fitted battery's capacity and cold-cranking rating against the handbook, and re-torque every connection that was disturbed.
- What fixes it
- Remake the joints; fit a battery of the specified rating. An undersized battery cranks slowly from the day it goes in.
Codes that produce this symptom (4)
Listed with the codes that most typically present this way first — the likeliest place to start.
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
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