Strange starting problem.

I've only seen on post regarding this issue and no real or clear answers. The car is a 2002 jetta TDI

When the temp gets below 60 degrees the car will not crank. All lights come on, the glow plugs work and the headlights go out but absolutely no crank. Above 60 degrees the car will crank and start with zero hesitation. Temp drops below 60 and no crank again.

Checked all grounds and connections to starter. No broken wires and no corrosion. Check battery terminals and no corrosion. Battery is 1 year old.

Anyone have this issue before and have a culprit?

Thanks.

I had this problem or a similar one for awhile. It would start when warm but not even crank when cold. It turnout out to be a bad battery terminal connection. You said you've already checked the terminals though, so don't know any other things to check.

Hmmm. Maybe I will give a good brushing to the terminals and grounds and maybe use a little dielectric grease and see if that helps at all.

To be more clear, when you say it doesn't crank, the engine doesn't turn over at all? Or slow turnover? If there's no engine turnover then it's most likely a bad cable to the starter causing high resistance. Make sure your grounds and hot wires are all clean.

Correct. No turnover whatsoever. Once above 60 degrees car starts fine. I'm not real smart on electrics but I'm wondering if possibly the temp is causing slight expansion enough to close the circuit. Don't know if this could actually happen? Or, perhaps warmer temps allow more current flow?

Aceshigh21 said:

Correct. No turnover whatsoever. Once above 60 degrees car starts fine. I'm not real smart on electrics but I'm wondering if possibly the temp is causing slight expansion enough to close the circuit. Don't know if this could actually happen? Or, perhaps warmer temps allow more current flow?

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Dunno about VW, but this definitely happens in some years of Mopar/Jeep vehicles - bad capacitors on the computer board.

Since the starter circuit doesn't use the ECM at all, it could be a bad start relay as well. Yours an auto or manual?

Its a manual trans.

Another piece of information. The coolant temp sensor has started to go bad. For a while it would start to indicate properly then drop to zero. Then it wouldn't work at all but car would still start. Now its back to working but not at 100 percent accuracy. Tends now to hover a tick mark away from 190 degrees. Don't know if somehow the start problem and the coolant temp sensor are interrelated somehow that I'm not aware of?

When problem occurs did you check for voltage at the starter (small wire) when you crank it?


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I have not done that yet. When it acts up again ill set the multimeter to it.

So found out what the problem was. Very thin coating of corrosion on inside of positive battery clamp. You couldn't even see the corrosion. Just enough to keep the electrical transfer to be too low. I scrapped the positive battery post and the inside of the positive battery cable clamp. Car started right up.

Glad you found the problem


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Aceshigh21 said:

So found out what the problem was. Very thin coating of corrosion on inside of positive battery clamp. You couldn't even see the corrosion. Just enough to keep the electrical transfer to be too low. I scrapped the positive battery post and the inside of the positive battery cable clamp. Car started right up.

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heh
on my old LTD I had a weak starter one day after work, hopped in, wouldn't crank. Well, got tools with me guess I'll get her done here and now.
jumped it with a set of cables at the solenoid on the fender to a separate battery, barely cranked
yanked the starter, cleaned the commutator, pole shoe contacts, and cleaned out about a pound of ground up brushes, spun strong on the bench with a portable jumper pack
get it back in the car and it barely cranks, even with those same jumper cables and battery I used before
at this point it is 10pm, 20 below and the orielleys across the street is closing so I wander over and grab a starter they got on the shelf. Toss that in there and it is weak as heck too.

Positive battery terminal was loose. Jumper cables were junk. Me being cheap as heck, I swap the old starter back in one last time and drive home at about 1am, returned the new starter the next day to get my $50 back.
7 hours at 10 to 25 below. I blame the cold for making me stupid.

Since the headlights go out, we know the starter circuit is excited. So the battery is bad, or connects are bad, sometimes the fat wire to the starter will corrode from the inside out. If that stuff all checks out, get a nice new or certified quality Bosch rebuild. You can also rebuild the starter yourself, components are out there, can be hard to find, but a starter is fairly simple.