Citroën C4 Grand Picasso 1.6 HDi (2008) – starter struggles

[MOL]

Hi everyone,
I’m hoping to get some advice from people with PSA experience, as I’m stuck with an intermittent starting issue that hasn’t been solved despite multiple parts being replaced.

Car details:
Citroën C4 Grand Picasso
2008, 1.6 HDi diesel, Manual gearbox
Approx. mileage: 274000
Problem description: The starter does not crank reliably. Sometimes it starts normally, other times the starter turns very slowly (“tired cranking”) or fails to crank properly.

Important context:
The day before the problem appeared, I drove about 200 km in cold weather without any issues.
The next day, the car suddenly would not start at all (no clicking or anything).

Work already done:
Battery tested and confirmed OK (new)
Starter motor replaced
Starter relay / starter control box replaced (the old one had melted / overheated)
Wiring has been “checked/measured” by the workshop
Despite this, their is still problems: The starter sometimes cranks well, sometimes very slowly, as if it is overloaded or losing voltage.

Observations / concerns:
A melted starter relay suggests high current draw or excessive resistance somewhere
I’m concerned the root cause has not been found, only symptoms treated
It feels like either:

excessive current draw from the starter
voltage drop under load (ground or main positive cable)
heat-related or intermittent fault after longer drives

Questions:
Are there known weak points on the 1.6 HDi (2007–2009) regarding:
engine/gearbox ground straps
main positive cable to starter
BSM (engine fuse box) issues
What is the correct way to diagnose this properly?

Voltage drop test under cranking?
Measuring starter current draw (amps)?
Is it common to see new or remanufactured starters that are faulty or draw too much current on these engines?
Could heat from the long drive (200 km) have triggered an underlying electrical weakness?

Any guidance, known fixes, or specific measurements/values to look for would be hugely appreciated.
I’m especially interested in voltage drop values during cranking and normal starter current draw figures for the 1.6 HDi.
Thanks in advance!

[PaulC5]

You could check the engine/gear box earth strap is in good condition and clean up the bare metal (strap and body/casing) at each end where it bolts on. After starting, turn it off and then check if the starter motor main cable is hot suggesting a bit of a break in the wiring.

Before the first start of each day for a few days measure the battery voltage and then see how well it turns over. This might give you an indication if it is a low battery voltage or elsewhere causing the slow turnover.

Was the new starter motor a new one or reconditioned and a good make ?