MK7 New Batteries - Wont start / turn over

[Whal]

Gidday, my 2011 Mk7 RWD transit always had a few issues starting clean. It would quite often turn over slowly or sometimes not start first try, as if low battery, but would always start after a few tries.

I have the dual battery setup and noticed that the previous owner had changed the rear starter battery, but left the original front one, which was now dead. I replaced the battery thinking the dead battery may also be dragging down the newer starting battery.

When I went to start after replacing, there is a sound as if the engine is trying to turn over, the van jolts a bit, but wont turn over, then a releasing sound when the key is turned back. Sound clip when starting below for reference. Any ideas what it would be? Starter motor packed in?

Van Start.mp3

Cheers
Whal

[tranmx2]

Sounds like the solenoid switch plates are dirty from arcing. Could be there is a resistance either supply or return. Did you check the contacts of the earth strap?

[metalworker0]

I can hear the solenoid taking the pinion gear into mesh with the flywheel ..then it seems it has not the power to start turning the flywheel .

I would start checking all the thick cables earths, positives etc ..take note there is a braided short cable on the outside of the starter between the solenoid and the starter ..that is exposed and corrodes. you need to take them off clean them , wire brush etc ..and re-install.

Also ... with ignition off, try getting a spanner on the crankshaft and turning it clockwise about 20 degrees or so, if it starts after that ..then it proves ring gear wear, you see: when an engine is turned off, it will always stop in the same place, the ring gear will always wear out in that one place. sometimes there are burrs on the ring gear that can be filed off. you are turning the flywheel to another place to prove if its that or not. you can also do this by putting into gear ..and rocking the van to another postilion .

..If no luck after that, you may need a new stater motor ..or at the least disassemble the starter motor ..clean it out and inspect the brushes . they can stick in their holders with build up dirt and carbon dust..or have worn short and need replacing.

all the best.mark