Technical Fiat Ducato 2008 Intermittent Starter Issue

[harrybo]

Hi there,
New to the forum but have scanned a fair bit for advise on this matter as a guest. I'm having solenoid issues with my starter motor where sometimes motor spins but doesn't engage the flywheel, if i repeat if finally works after sometimes 1 or 10 tries! Í initially assumed faulty solenoid so i pulled it off gave everything a clean and still had issues.
I got lazy and bought a second hand starter motor to just swap out but this one doesn't even engage the solenoid át all. I tested both motors and solenoids with jumper cables to the battery and both actually work fine, (should of done this before buying another one..) so i assume the second one is maybe more sensitive to a low voltage trigger than the old one (it has a longer spring in the solenoid).
I grabbed a volt meter and tested the ignition wire and i get 12.4v when the cable is disconnected (grounding to starter case) however i only get around 10.5v when it is connected to the starter... I found the junction D004 and gave that a clean and also gave the earth strap contacts a clean although i'll replace the cable later this week just in case...
I also pulled the ignition switch apart and i noticed the voltage dropped to 11v on the 12v in pin (30) with ground to the bodywork when i turn the switch to ignition (not sure if that means anything..)
I also got 0.2 Ohms resistance for the ignition cable from the ignition switch to the connector for the starter which i assume is fine.
can any tell me anything else i can check?
I also gave the battery a charge overnight to ensure that wasn't an issue as the van has sat for a few weeks (issue was present before this)

worst case i was thinking maybe add another relay next to the starter that is triggered off the ignition switch wire to supply the 12v voltage from the battery connector on the solenoid to the ignition terminal on the solenoid... but would rather find the actual issue if possible.

 

[the green vanper]

also gave the earth strap contacts a clean

Hello

Which one? Battery to body, or body to engine? Or both? If not, check the other one, too.

In general, those are crap in the triplets, I'd check all of them (also the ones from body to fuse/relays boxes). There is a diagram in eLearn that shows them all.

 

[harrybo]

I

Hello

Which one? Battery to body, or body to engine? Or both? If not, check the other one, too.

In general, those are crap in the triplets, I'd check all of them (also the ones from body to fuse/relays boxes). There is a diagram in eLearn that shows them all.

Hey, thanks for the reply! I just did the body to engine initially but i went and cleaned up the body to battery this morning which sadly hasn't helped.. i'll check the other ones after work today as it takes me a while to navigate the eLearning software for electrical stuff.

 

[the green vanper]

You can have a look at it. It's an automatic translation from German, so bear that in mind. But it seems more or less precisely described

 

[Cornish Ian]

As you seem to be seeing some low voltages, the first thing I would try is a known good battery or at the very least some decent jump leads.

 

[the green vanper]

As you seem to be seeing some low voltages, the first thing I would try is a known good battery or at the very least some decent jump leads.

The OP wrote in the first post that he has charged the battery overnight, but yes, if the battery has some internal short circuit, the voltage can drop significantly under charge (even under the critical voltage level). And charging won't resolve the issue.

 

[Anthony489]

Hi harrybo

From your description it sounds as though you are getting excessive voltage drop somewhere. If the solenoid doesn't get enough voltage/current it won't have enough strength to engage the pinion. I suggest you go over the circuit that feeds the solenoid via the ignition key switch (see schematic) and check all junctions, fuse contacts etc. Even though the solenoid doesn't draw nearly as much current as the starter, it still needs a fair old bit (maybe 30 Amps) to pull in so low resistance is important. If you really do have 0.2 Ohms that's too high, it would lose 6 volts at 30 Amps.

The main gearbox to chassis strap tends to corrode internally, and cleaning the terminal faces does nothing to help this. Best to change it as a precaution.

 

[the green vanper]

The main gearbox to chassis strap tends to corrode internally

The best is to replace and add a second one. The wire should be isolated and the connections to terminals should be heat shrinked to minimise possible water ingress. I'm using a good quality, typical welding wire (=not the wire used to weld, but the wire which is used to make the lead cable) (pure copper of course) of the appropriate diameter + copper terminals. It's also good to add a little bit of non corrosive silicone or some other sealant inside the heat shrink.

 

[harrybo]

Hey thanks for all the replies, you've all been super helpful!
I won't be able to get to the shop until Friday so will replace the earth strap from the gearbox to body and let you know if that changes anything. I'll check all the other earth's and the resistance between both sides of D004 in the mean time as well. It may of just been the way I measured it was inaccurate.
Thanks again

 

[Communicator]

Hey thanks for all the replies, you've all been super helpful!
I won't be able to get to the shop until Friday so will replace the earth strap from the gearbox to body and let you know if that changes anything. I'll check all the other earth's and the resistance between both sides of D004 in the mean time as well. It may of just been the way I measured it was inaccurate.
Thanks again

To confirm a faulty gearbox earth strap, the use of a jump lead between an engine lifting lug and a clean chassis earth point, is commonly suggested.

Trying to measure resistances of less than 1 Ohm with a multimeter is stretching its capabilities. Probably better to measure voltage under load at various points, to a common reference such as battery negative terminal.