Hi all wondering if you can help. I've just rescued a 1999 300tdi auto from the scrap man been sitting in a field for 2 years. Done all the work to her but it's got a starting fault and it's driving me crazy. it started that I thought battery was duff so I bought a brand new yuasa one and it started. Great. Now I came back to it the next day and it started although sluggishly, left it run for 30s and knocked it off happy that it started. Went to start it again then two mins later and it was like the battery was dead flat, turning over really slowly and pulling all the interior lights down etc. took ages then with jump leads off my tractor to get it to finally burst into life. I left it that night then with the battery disconnected and it started fine next day so I thought something must be on. I had a friend test my theory with a multimeter and it was only drawing 0.02amps so nothing is left on! I've stripped the negative terminal off the car (body and chassis) and wire brushed them spotless and refitted with a blob of grease. I've tested the alternator in that it reads 14.1v when charging and the car will continue to run if the battery is disconnected, I've taken the starter and had it all tested at an autoelectrical centre and by a mate and it was perfect, I've run a separate earth from neg terminal to engine but all to no avail! When I left it yesterday it had 13v in the battery, when I went back this afternoon it only had 11.1v but it still started and I started it about 20 times in a row and it started every time! What else can I do? Where else are the earths apart from the one from the neg to the body to the chassis, and the starter one?
I'm clutching at straws now why is it still draining
Cheers!

Could be an intermittent dead short? It is possible that there are bared wired on a perm live cicuit that touch but burn over and stop contact.

I replaced a starter on a V8 earlier this summer that had simmilar symptoms but kept eating alternators, it turned out to be a badly corroded "EYE" on the starter cable that was restricting current flow in the circuit, once discovered I swapped it out with my winch power cable to get them back to the UK and it never missed a beat and didn't eat anymore alternators either. Could it be a bad contact either + or -?

I am not 100% on the earthing but the battery goes to the chassis leg the chassis has a strap that goes to the gearbox and should go everywhere on the engine from there.

It is a common mod to fit a new earth direct from the battery - to the engine using the outer most timing cover bolts or the unused aircon bracket mounting lugs.

First advice is to fit an isolator between battery and earth to conserve the battery, then follow the cables on both sides to see whats what, clean any and all contacts and ensure they are tight when re-fitted and cover them in vaseline to prevent further corrossion.

My Disco is over 23yrs old and uses all original earthing points with all new straps and meticulously cleaned earth contacts that have been protected from corossion.

Never thought of that thanks will trace the positive tomorrow and have a look I'm very new to electrics lol only learnt how to use a multimeter since I've had this car haha. I've followed every inch of the earth it runs from the battery to a p clip onto the inner wing then carries on down to ty chassis leg which I've taken all off and cleaned and put back on with a blob of grease, will try the same then with the positive tomorrow.
Would it do any harm to just find some odd cable and run it one from battery to body, one from battery to engine etc as extra earths?

Immobilizers have been known to drain batteries.

I've considered that myself or the alarm but how would I test that? Need to disconnect it and the alarm really but can't imagine that to be easy as if it was that easy it would be easy to steal lol

Disconnecting the battery with the engine running can destroy an alternator and if the car has ECU's it can damage them too, alternators are also a common cause of battery drain.

jimbo-td5 said:

Never thought of that thanks will trace the positive tomorrow and have a look I'm very new to electrics lol only learnt how to use a multimeter since I've had this car haha. I've followed every inch of the earth it runs from the battery to a p clip onto the inner wing then carries on down to ty chassis leg which I've taken all off and cleaned and put back on with a blob of grease, will try the same then with the positive tomorrow.
Would it do any harm to just find some odd cable and run it one from battery to body, one from battery to engine etc as extra earths?

Click to expand...

Extra earths are fine, you can use jump leads as temporary extra earths or positives but bad earths will not be the cause of battery drain only possibly the cause of poor charging.
Grease on connector surfaces is not a good idea as it's not a good conductor, on bolt threads is OK though.

I think I may have found it, while playing last night with all the electrics testing ready for MOT when I flicked the lights on and off the radio burst into life! It's never worked since I had it, so I tried again and every time I turned the car on the radio didn't work until I cycled the light switch, so this may have been coming on or trying to turn on the whole time, I pulled it out and fitted the CD player I already had to it and it seems to have been fine ever since, I'll soon find out tho the next time it doesn't start lol