Technical Doblo MPV - Battery to Starter Pos cable - poor connection ??

[OldGeek]

I've had a problem with my 2008 Doblo MPV for a couple of years now, so I can relate quite few symptoms, which hopefully will help track it down.
It's a very poor cold first starter, even in the Summer. Once it's been started in the morning, it's then fine at starting for the rest of that day.
I think I can disregard most of the usual 'Winter' culprits, it has a brand new battery (the 2nd one I've tried),
I checked the heater plugs, all ok.
The Alternator charges fine - 14.2 volts.
....but here's the clincher, even though the battery is fully charged, when I attach my Lithium jump starter in parallel, she starts within a couple of seconds of the first cranking.
So it's just like there's insufficient cold cranking amps to spin it fast enough to catch.
The battery is the correct size, and is charged, so it isn't that.

So my latest theory is that the cable that runs from the battery pos directly to the Starter and Alternator may have a poor or corroded connection, restricting the amps that can get to the starter motor. So when I effectively double the maximum cranking amps with my lithium jump battery it overcomes the problem.

Easy enough to check visually I know, but a bu**er to get at with that damn under tray in the way.

 

[the green vanper]

Hello,

Check the grounding points on the body. And the ground cable which connects the engine / gearbox to the body.

The cables tend to rot inside, it's not visible, but the resistance gets very high.

 

[the green vanper]

That's the list of all earth points, but can't find a diagram which shows all of them on the van:

C001 BATTERY EARTH
C002 BATTERY EARTH ON ENGINE
C003 BATTERY EARTH ON BODYSHELL
C010 LEFT FRONT EARTH
C011 RIGHT FRONT EARTH
C012 ABS FRONT EARTH
C015 DASHBOARD EARTH, DRIVER''S SIDE
C030 LEFT REAR EARTH
C040 ENGINE EARTH
C050 AIR BAG EARTH
C053 SIDE BAG + HEAD BAG EARTH
C054 PRETENSIONER EARTH
C060 INJECTION ECU EARTH
C062 METHANE INJECTION CONTROL UNIT EARTH

 

[the green vanper]

OK, found it

and MY2005:

 

[OldGeek]

Thanks for the replies Vanper.
I'll check those as you suggest.
I now have to pray for reasonable weather ! I'll have to take the sump guard off to get at them, and I do have a pair of ramps, but it'll be out on the driveway. (brrrrr !)

 

[OldGeek]

I haven't been able to check the earth straps yet because they're mostly underneath and I'll need to remove the undertray, and it's freezing cold here at the moment.
I had a brainwave though, to be able to test whether there was poor continuity between the battery neg terminal and the engine block. I clamped a heavy duty jump lead between the battery neg and the engine block,to provide a temporary parallel path.
It made no difference to the cold cranking though, it didn't fire up after three attempts.
I then removed the jump lead, tested the battery and found it was 12.9 volts, and connected my lithium battery pack jump starter and the engine started after 1 second of cranking.
So unless my starter motor is somehow demanding a much higher cold cranking amp battery, I'm thinking it may still be the positive circuit between the battery and the starter motor. My theory is that the much higher cold cranking capacity of the good battery and the lithium jump starter in parallel is able to get through the possibly increased resistance of the maybe corroded terminal on the starter .
I believe that cable from the battery pos is also the feed to the glow plugs, so maybe that's adding to the problem in cold weather, limiting the amps they can get during the glowplug timer period.

 

[the green vanper]

I like the way you think and analyze

Coming back to the first post: you wrote you are sure the battery has the correct size and is fully charged. Are you sure it is not damaged? Usually a tester which applies a huge load to the battery terminals (I don't know the proper English name) is better than those cheap electronic ones.

The first thing to check is the battery CCA with the Doblo specification. Batteries can come in the same physical size and capacity (Ah), but have different CCA. Usually the ones with smaller CCA are for gasoline engines and cheaper, bigger CCA is ment for diesel engines and usually costs more.

Perhaps someone put a gasoline battery in a diesel vehicle?

 

[OldGeek]

I like the way you think and analyze

Coming back to the first post: you wrote you are sure the battery has the correct size and is fully charged. Are you sure it is not damaged? Usually a tester which applies a huge load to the battery terminals (I don't know the proper English name) is better than those cheap electronic ones.

The first thing to check is the battery CCA with the Doblo specification. Batteries can come in the same physical size and capacity (Ah), but have different CCA. Usually the ones with smaller CCA are for gasoline engines and cheaper, bigger CCA is ment for diesel engines and usually costs more.

Perhaps someone put a gasoline battery in a diesel vehicle?

I have to admit that all of the symptoms do point so strongly to a bad battery, it sounds so much like that. Year ago I remember a Guy in a car spares shop telling me how many customers came in at the start of Winter, buying first the magical 'battery pills', then a battery charger,and then finally biting the bullet and getting a new battery !

I can be 99.9% sure it's not that though, because I bought a brand new battery last Winter, and AGM, of the correct cranking amps, (though I would have bought an even bigger one if I had the space to fit it). The starting trouble persisted though, so this Winter I bought another, conventional wet cell battery, again of the correct cranking amps, in case the AGM was faulty.

Hence my theory that it must be the wiring, or a relay,or the starter motor itself.
Here's a link to the actual first battery that I bought, (that gave the same problems). https://www.amazon.co.uk/gp/product/B00PKLV7RY

 

[the green vanper]

I thought about the battery because you haven't mentionned it was replaced.

A bigger battery is not a good solution, unless you change the alternator, too. Unless with the smart alternators (though I don't know if a 2008 Doblo has it) it is possible to reprogram the size of the battery so that the alternator knows that is needs to charge the extra capacity.

If the battery is new it would be good to finish eliminating the wiring. I'd use a jump cable to double the battery - starter positive lead.