Sluggish/no start diagnosis

[eddiec]

Hi there,

Wondering if the wise-ones on the forum could help me with a little problem related to the start-up electrics on my 300tdi....

It's been a long saga, but first to clarify that it's a fairly new battery, and I have a traxide unit running an additional two batteries (one extra under the seat, one in the cargo area).

For a while I've been noticing that if I left it for a week and tried to start up it would struggle, so I assumed it was some drain on the battery, and just kept it on the charger instead. However more recently I've noticed that the battery doesn't seem to be discharging that much (noticeable both by checking the voltage and the fact that the blinky light on the traxide was still solid) but would still have problems starting if left for more than a day.

Once I'd started it once for the day and let it run for a bit it seemed fine starting subsequent times - for that day at least. So for the last few months I've just charged it the night before I knew I'd need it and generally it was ok. I noticed it seemed to get a bit harder to start after its last service when the timing belt was changed - Not sure if that's a coincidence.

This morning I had it on the charger from the night before, went out to start and it just wouldn't go. Starter would turn it over slowly a couple of times, but not enough to get it going....

Any ideas? I know electrical gremlins are often impossible to diagnose from vague descriptions, but is there anything simple I should be checking before I take it to the shop? Could it be a problem with the connection/earth to the starter motor? That's the only thing I can think of currently. The earth from the battery/chassis seems fine and I recently refreshed....

Thanks muchly....

[rangieman]

Have you had your battery load tested also what is the cold cranking amps CCA of your battery , I recently changed to a yellow top 780 CCA battery and it works great for me , I did have a 650 CCA battery which struggled on cold mornings or when left for a period would stuggle:cool:

[steveG]

I'd start by checking the battery voltage before you go to start it.
If its under 12v then its probably too low for a good start. Either it isn't charging up properly and/or something is draining it (or simply self discharging).

Steve

[drivesafe]

Hi eddiec and do you disconnect the other batteries or just let them all charger together ( recommended ) ?

Either way, if you had the battery(s) on charge all night, then there is a serious drain/fault somewhere.

Also, have you checked all your cable connections, particularly the negative/earth connections?

[Blknight.aus]

Also, have you checked all your cable connections, particularly the negative/earth connections?

thats where Id start

[eddiec]

Thanks for the feedback...

Yes, I've checked the voltage. Doesn't seem to be dropping that rapidly and I'm starting to think that's not the problem. After all, it had been on charge all night last night, the Traxide blinky light was solid, and it still didn't start. I've checked it in the past and even after a few days it was well above 12v, but I know from experience it would struggle to start. But I'll double check, thanks.

I'll start with the earths, definitely. Given I haven't touched the starter motor in a few years, nor has anyone else, it's quite possibly in poor shape.

And yes drivesafe, I do leave all the batteries connected whilst charging. Second battery is permanently connected and the third only comes out while camping, otherwise they all remain in and connected.

Thanks again.

[camel_landy]

Unless it has been modified, the earth for your starter comes from the earth strap connected to the transfer case.

This is usually fine, straight out of the factory but once the units have been split for a clutch change, etc... Grime gets on the surfaces and you eventually loose the electrical continuity.

I had similar issues on mine, so I ran a lead from the -ve, straight to one of the starter fixing bolts which cured it... and the 'over heating' problem I had!!

M

[eddiec]

Unless it has been modified, the earth for your starter comes from the earth strap connected to the transfer case.

This is usually fine, straight out of the factory but once the units have been split for a clutch change, etc... Grime gets on the surfaces and you eventually loose the electrical continuity.

I had similar issues on mine, so I ran a lead from the -ve, straight to one of the starter fixing bolts which cured it... and the 'over heating' problem I had!!

M

Thanks - that's exactly what I'm going to try... Tried to get in there on the weekend to clean the earth on the starter but of course you can't reach it without removing, and the bolts are way too tight for me to budge. So I'll try that fix!

[camel_landy]

As a temporary 'Let us see if that would fix it' kinda thing, try just using a long jump lead from the -ve on the battery to the engine. That way, you'll be able to see if improving the earth connection will solve your problem...

...and therefore make it worth the 'spanner rash'. :D

M

[eddiec]

The plot thickens....

After having it on charge for a few days I popped out tonight. Battery was up at 12.7 volts or so... Poked around the engine bay and measured voltage between positive terminal of battery and bolt on starter motor. Much the same...

Turned the key and it fired up no problem...

Decided to check the voltage across the battery now to see how the alternator was and, at idle, the voltage was now LOWER than it had been. 12.4, no more. Turned the engine off after a while and the voltage across the battery went back up to about 12.5 or 12.6..

Is this the sign of a bad alternator? Or is there possibly something else at play here? Or am I just not understanding auto electrics particularly well?

[justinc]

Alternator should see at least 13.6V and up to 14.4V at idle with a Tdi. What happens when you hold the revs at say 2000rpm?

JC

[eddiec]

Alternator should see at least 13.6V and up to 14.4V at idle with a Tdi. What happens when you hold the revs at say 2000rpm?

JC

With a bit of throttle it was reading up to 14V (no tacho so I can't be precise)

[roverrescue]

My guess,
One of your other two "secondary" batts has a dropped cell or other issue.
Once engine starts it pretty quickly gets up to the switch over voltage of the traxide.
Current will then flow from good batt to dying/dead battery and evaporate as heat.
Slowly pulling the "good" starter down each start/stop cycle.

Just for giggles disconnect the two secondary batts for a week or so and run with a single good starter and see what happens.

S

[eddiec]

Thanks - that's another worth exploring. Although I'll be ****ed if that's the problem, as the secondary/tertiary batteries were expensive AGMs and are only 4-5 years old...

[roverrescue]

My guess stands even stronger then ;)

S

[camel_landy]

Yeah, I'm with 'roverrescue' on this.

FWIW - I don't bother with 'fancy' batteries any more. I've tried Optima & Oddessey and found them to be :angrylock:.

I've gone back to lead-acid these days.

M

[roverrescue]

Agreed with camel...
and with regards to "fancy dual battery systems"

0 B&S between the positives and a use a voltmeter

When the voltage gets low do something
Better for winching and as long as you use your brain less hassles.

If per se your problem is a dropped cell in one of the secondary batteries... had you just a linked system you would have noticed a slight decline in overall system voltage performance as the dropped cell has a consistent effect on all three batteries at all times... I can almost guarantee it wouldn't leave you with a 'no starty' unless you allowed it.

S