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Sometimes slow starter, bad connections?

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Its a 91 GT, it had a brand new Bosch silver battery at the beginning of summer, the little box of electricals was replaced in the alternator in the winter (the alternator was new in 2002) , and the current starter was fitted last week, this is an original one stripped by myself and rebuilt with the correct lubrication.

Basically sometimes the starter can be slow to turn the engine over, like the battery was low, yesterday away from home this happened to the point it wasn't turning over fast enough to fire, the engine was hot at this stage (been sat in traffic) I left it 30 mins to cool, it then turned slightly faster and started immediately. After running for a couple of mins when switched off and started again the starter was fast firing it instantly.

The reason the battery was replaced was because i thought this was the cause, then i refurbed a spare starter because the other wouldn't always turn over, but now i'm wondering if its something else? The leads from the battery to starter to alternator all look fine. I did check with the 12v test light when it wouldn;t start and the battery lit it up nice and bright, checking the earth of the engine that lit it up bright too.

The battery terminals look clean but are not coated with anything to stop corrosion, could this cause this problem? All connections are tight. The alternator light goes out immediately when started, this problem is only intermittent. Any ideas?I'm going to test battery condition and charge rate later but i don't think its that.


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  • VolksKid83


  • john.p.clegg


  • chrisjb330


  • caretakerplus



Intermittent faults are always a swine to locate.

Just to eliminate the possibility, it would pay to make sure that the engine itself is 'free' to turn over when the fault occurs.

Coating the battery terminals with petroleum jelly etc is always a good idea, as you say, it prevents corrosion, but it wont make the slightest difference to the batteries performance if the terminals are clean and tight.

Fully charge the battery.

You then really need a voltmeter connected first of all between the battery positive (+ve) POST (not the clamp) and the starter main TERMINAL (not the cable lug)

Get an assistant to operate the starter - the meter should NOT read more than 0.5 volts, if it does, there is a poor connection.

Repeat the above between the starter case/engine and the battery negative (-ve) POST - again, no more than 0.5 volts should register on the voltmeter.

You can also check the solenoid contacts by connecting the voltmeter between the two main solenoid terminals (again, 0.5 v max)

Did you clean the commutator/brushes when you stripped the starter? If you fitted new brushes, did you bed them into the commutator?

(Fine glass paper wrapped around the commutator and rubbing against the brushes whilst you rotate/partially rotate either the armature or the end plate, is the way to do that)


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Excellent, thorough as always caretaker!

I did clean the commutator whilst it was in pieces, the brushes were nice and long so i left those alone, the starter worked perfectly on the previous car so i didn't mess with that too much. The original starter to this would sometimes not do anything (a dull thud could be heard from it if you were near), tapping it with a hammer would solve it. This is the reason i changed the starter but now i'm thinking it could be something else.

I will do that test, will be fun holding the meter to the starter terminal! I went to check battery connections today but ended lifting out the battery, long story short theres an arm sized hole in the battery tray now that i'm sorting! :angry:

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  • 2 months later...

So this isn't solved yet, I have been over the engine with a multimeter, the battery registers about 12.62v when cold, and about 14.5v when idling. I can get exactly the same voltages moving the negative probe to different points on the engine with the positive probe on the battery terminals.

And i just did the same test with the engine hot and got the same results, however i could not start it to test when idling.

I have had suggestions of similar problems on long block engines where its turned out to be the bush the starter motor armature slots into in the gearbox. Such as:


Obviously that will be fun to change given where it is on a short block lump. My first job is to remove the starter, clean that bush with methylated spirit and reassemble when i go home for christmas (i don't have sufficient tools here). But i just wondered if anyone else had suggestions? This problem is really annoying!

Also, when cold its getting close to not starting, it resets the digital clock every time. I'm going to get this brand new battery tested when i'm home since it has a three year guarantee.

Edited by VolksKid83
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one thing I've always done with old vw's is make up new heavy duty cables for the battery ...seems to help alot

what you could do if you want to be sure , use some jump leads to run batt to a good earth and another to the starter + (might be tricky)

if its better with either of those then make or buy some thick cables ..wont cost alot if you diy

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What I did once,and it helped ,was to make a jacket out of thin insulation for the battery,sides bottom and top,it certainly helps the battery on cold winter mornings...

John :wink:

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Would be worth changing the starter cables. My original one broke before i bought it and a smaller one was put in place, that one eventually broke and took me 10 min to figure out why it wasnt starting, basically it was starting with 1 core contact to the starter for a while.

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