I recently renewed the certificate of entitlement on my car. It has been reliable except that lately, the cranking during start-up is very slow. I replaced the battery, which was about a year old. Despite that, the cranking improved only a little initially. What could be the problem?
Slow cranking is usually attributable to a worn starter motor. If this has never been replaced, you might want to consider doing so, as it could eventually fail and not crank at all.
There are, however, wiring issues that could also cause slow cranking. Old wiring in some cars has a tendency to drop in current-carrying capacity. The reason is that the multiple copper strands in the insulated wires can break with age.
Unfortunately, there is no easy way of determining which wire is affected. So the best solution is to replace the complete set, including the earth-link between battery and engine.
Bear in mind that prolonged use of such weakened wires can cause heat build-up in the wiring loom that can lead to breakage in the insulation.