Ducato Fait Ducato 3.0 starter battery discharge in 3 days

[magicmax]

Hi to all,
I purchased a Fiat Ducato 3.0, A class Motorhome last November, quite high milage for a motorhome,
65k, had many engine problems since then, and the previous owner denide any knowlage of all the problems,
but lets give every one a chance to sort this one for me,
engine is slow to crank but fires right up if it turns fast enough, from the start it sounded a bit slow on cranking,
then one day just click click, then nothing, removed started, bench test, worked fine, cleaned and lubricated,
and refitted, still click, so tested the battery, disconnected terminals and fully charged,
then battery tester and load test, all good, give it another recharge just to top up after the load test,
all back together and slow to to crank but started right up,
so removed earth stap, s*d to find, down the back of the air filter, top of gear box to subframe mount, about 6in long
checked, cleaned and replaced, still no diffence, slow to crank, then ran a second earth strap, 200amp
cable, from one of the starter mounting bolts to the earth bolt beside the slam panel, still no difference,
replaced the earth strap from the battery clamp to the earth bolt beside the battery box,
no difference,
any ideas, any one
And now for the next problem, starter battery discharge, battery discharges down to 11v in 48hr from fully charged,
yes it has an alarm, and no it is not on for all this testing, 10ma
it does have a radio, but just a basic sigle din alpine unit drawing 4ma,
the alarm has a test led, that tests to say the canbus has switched off,
yes it has a reverse camera, wired seperatly and has no current when turned off,
Have checked all the cables on the poss battery terminal
2 heavy leads going to the fusebox under the bonet and then to starter, no current when switched off,
2 20amp cables go to the distribusion box in the motorhome, why 2 i dont know as the charge system
for the starter battery is only 6amps, i can only assume its for high amps from the alt when charging while
driving, bit OTT for that,
next are 3 more leads and the one supplying the cab, cambus, dash, etc, now that does have a 1.5amp current,
but cant figure out what could draw that current when ign not switched on,
has anyone any ideas, ????

 

[Anthony489]

Hi magicmax

If your starter and battery are in good shape, the only other thing that could slow down cranking is the total resistance of the cables (including the earth return) and their various junctions. I don't know how you tested the earth strap, but these are known to suffer from corrosion within the crimped lugs which cannot be seen by visual inspection. This increases the resistance from an ideal 1 milliohm to something higher, but still very low by normal standards. Starter current probably peaks at 1000 Amps and then drops to 600 Amps when cranking, so ultra low resistance is crucial. I suggest you replace the strap anyway, probably cheaper to get one made up than pay Fiat prices, but check first. If you prefer, you could use a test voltmeter with extended probe wires to measure the voltage drop between the engine block and the battery negative terminal whilst the engine is cranking. I'd expect to see no more than 0.5 volts. The other component worth checking is the junction A005 which incorporates the "Jump Start" point (under a plastic shroud near the under bonnet fuse box). It's possible the bolted connections have corroded.

Next to the battery is a "Maxi Fuse" fusebox, which is the first stage of fusing. There are 5 fuses as standard:

A special Cal4 Fuse for the starter motor
F70 (150 Amp) which supplies the B001 Fuse box/junction unit in the Engine Compartment
F71 (80 Amp) which supplies the main part of the B002 Fuse box/junction unit under the Dashboard
F72 (70 Amp) which supplies the secondary part of the B002 Fuse box/junction unit under the Dashboard
F73 (50 Amp) which supplies the motorhome converter's socket

Be aware that Fiat changed things over the years, and the motorhome converter may have added their own wiring/fuses. Don't worry about the paired "overkill" cables, they are presumably to carry the high charging current from alternator to leisure batteries with minimal voltage drop.
The "leakage" current of 1.5 Amps is quite high. To track down where it's going, the only thing I can suggest is to be methodical and follow a programme of removing fuses one at a time (including the ones at the next stage after the maxi fuses) unit the current ceases. I assume you have eliminated the interior light ? Faulty alternator diodes can also give this effect, but I think you have discounted that.

 

[madwrx]

i,d be interested if you get a decent answer to this ,our 3.0 litre is also slow cranking to the point that i thought the battery past it,s best ,,a brand new unit recently hardly changed it ,,it,s possible thast the 7-9 litres of oil in these engines have ,take a larger drag from the whole system to push the starter through, certainly seems a bit peppier with higher ambient temps recently,,will have a look at our engine /body earths as well to see if it makes a difference

 

[Anthony489]

Hi madwrx

The load on the starter is mostly the compression, plus some drag from the pistons/rings and the valvegear. Bearing friction won't amount to much. Warmer/thinner oil will reduce the drag a little, but the main effect will be to improve battery performance. The amount of oil won't affect any of this, the crankshaft is well above oil level so there's no drag from dipping into the oil.

If changing the battery offers no improvement that does rather point to a bad (high resistance) joint somewhere in the main starter wiring.

Let's hope the original poster reports back with an update.