Hello,

I have I problem that is driving me crazy !!!!

My MK Indy has an Ecobbost 1.6 engine with Delta ECU.
I made about 7000 km and everything is fine but, once every 3-5 engine starts, the starter motor seems not able to turn the engine.
When it happens, it is possible to ear the big "clack" of the starter motor relay and the voltage goes down (MXS Strada temporarly off in the same way when the starter motor works fine).
When the problem appear, the engine does not turn at all, while when the starter works fine, it turns very well and the engine start immediately (there is no intermediate situation like, for istance, there could be with a tired battery).
The fact that the voltage goes down (so the starter is adsorbing power), made me think about a problem in the starter motor, so I replaced with a new one, but the behaviour is exactly the same.
I also tried with a different battery but the behaviour is the same.
When it happens, if I try to move a little the engine (by pushing the car and suddenly engage a gear) and then try again, very often the starter motor works

Does someone has experience or suggestion on a similar problem ?

Thank you!

Mauro

check the earthing straps to the engine / gearbox

if you have a new battery and starter, assuming the alternator is keeping the battery well charged, i would take the main battery lead conexions off and clean them up, also the earth lead.
if you get someone to hold the key over so the starter is taking current, sniff and touch battery leads to see if anything is getting warm

I have had similar problems recently, but they were caused by wear in the solenoid causing the plunger to stick before it was fully engaged - i replaced the solenoid (and also put some molybdenum disulphide grease on the plunger) - which sorted all my problems.
You've swapped the starter, so that should rule out the starter being at fault, here's a few things to consider:

Have you got an amp clamp that you could check the amperage draw when the starter is playing up? The voltage drop gives some indication of this load, but this is dependant on battery capacity as well. If your starter is 1kw, expect the inrush current to be 300-400a, and once steady cranking 150-200a.

Another thing is your wiring system, if you have a kill switch or other extra joins in the wiring system you can get a voltage drop on the connections or the actual switch, these little things can add up to a significant drop in voltage actually reaching the starter, this increases the amperage needed to spin at the same speed.

Is the clearance between the pinion and ring gear too tight? This can cause engagement issues, and can usually be fixed by moving the starter away from the ring gear with the bolts slightly loosened then retightening, half a millimeter can make all the difference. If the holes are dowelled then there is no adjustment, but this hopefully should be correct from manufacture.
This does seem to be likely with you rocking the car allowing the starter to engage properly.


Dave