Possible bad negative battery lead

[DeepBlue]

I strongly suspect that my negative battery lead needs changing. Reason I say that is due to the fact that I found a ton of acid and corrosion on the connector last year which i cleaned up, it feels rather hard, and car has had trouble with cold starts for ages in one form or another.

Is there a definitive DYI test one can run without specialized tools? I did some searching around and there is all sorts of crap out there which may or may not help diagnose anything.

Assuming that it is bad, is the swap process any more complicated than it looks?

It seems that I just need to buy this and https://www.ecstuning.com/b-genuine-volkswagen-audi-parts/battery-cable-negative/5n0971235a/ and remove one screw.

 

[GTI's]

How about a voltage drop test on Neg cable.

 

[eurocars]

x2 on voltage drop test. Set your multimeter to volts, one lead goes at the negative terminal on the battery, the other lead goes to the other end of where the cable connects at the body. Spec is usually less than 0.5v drop.

 

[DeepBlue]

Thanks guys. Seems pretty straight forward even for a relatively mechanically unsophisticated person such as myself. I have a multimeter on the way. Will try it out shortly.

How about the swap procedure? Anything to it? It seems like there is nothing to it.

 

[DeepBlue]

No drop in voltage it seems. Reading 12.4v on bat and leads overnight. Reading 14.3v when running.

This is a problem... as this issue has returned and I am REALLY tired of it at this point.

 

[GTI's]

So when you did the voltage drop test what was the result?

By the way how old is you battery, its at 75% overnight and the charging system seems ok.

 

[DeepBlue]

Battery is less than 2 years old. Just ran the test again...

This is what it looks like.

There seems to be quite a bit of a drop on some parts of the exposed negative lead connecting to the frame but not others. Bit odd, no?

 

[eurocars]

Looks like you're touching the lead to painted/dirty areas causing the lower reading. What did you get when you measured from the negative terminal of the battery to body ground

 

[GTI's]

Voltage drop test on negative battery cable, in this case 0 voltage drop

 

[DeepBlue]

Thanks guys.

Took off negative connector and cleaned both ends up with a wire brush. Voltage drop is now showing as 00.00 everywhere.

Hoping this will have a positive impact.

 

[DeepBlue]

No impact on the hard start issue... Dammit.

 

[Fred930]

I watched your video, where car cranked longer that expected on the first starting attempt. What makes you think there is anything wrong with your negative battery lead? The car seemed to crank just fine in all 3 cases. Suspect you have some other issue (perhaps low fuel pressure on initial start up?). The fuel rail should be pre-pressurized when you open the driver's door. Can you hear the fuel pump operate when door is first opened? You don't have a check engine light, but still would be a good idea to have the car scanned to look for stored errors.

But to your original point - assuming you have a set of jumper cables, simply run one of them from the battery negative terminal to a good metal ground on the car (in other words, use that jumper to parallel your normal battery negative lead). If the car continues to hard start on the first attempt, you will have ruled out the battery lead wire. But again, your car cranks fine, so I'm guessing the battery and starter wiring are OK.

 

[DeepBlue]

I watched your video, where car cranked longer that expected on the first starting attempt. What makes you think there is anything wrong with your negative battery lead? The car seemed to crank just fine in all 3 cases. Suspect you have some other issue (perhaps low fuel pressure on initial start up?). The fuel rail should be pre-pressurized when you open the driver's door. Can you hear the fuel pump operate when door is first opened? You don't have a check engine light, but still would be a good idea to have the car scanned to look for stored errors.

But to your original point - assuming you have a set of jumper cables, simply run one of them from the battery negative terminal to a good metal ground on the car (in other words, use that jumper to parallel your normal battery negative lead). If the car continues to hard start on the first attempt, you will have ruled out the battery lead wire. But again, your car cranks fine, so I'm guessing the battery and starter wiring are OK.

My concern regarding negative lead originated from finding it covered in lots of acid and corrosion. That, plus my sense that it felt a bit hard and inflexible when I was cleaning it. At this point, I pretty much ruled it.

My issue remains though. To answer your question, there are no codes whatsoever. I do not hear the fuel pump start up when I open driver's door, but I'm not sure if I ever did. This issue has been with me for possibly as long as several years. Lots of stuff done since but here are some highlights :

• Low pressure fuel pump
• Fuel filter
• Coil packs and plugs
• Alternator
• Timing belt
• Cam follower - barely worn
• Air filter
• MAF cleaning
• Carbon cleaning

I've been to a number of reputable shops in the area and they all seem to be at a loss. Which doesn't seem to prevent them from charging me diagnostic fees while they look for something big and expensive to stick in my @$$.

Just about gave up on finding someone who is actually able to diagnose this sort of stuff in total absence of any codes. I suppose I should search for a DIY way to check rail pressure.

This is for a mk4 but it seems like a good start - http://forums.vwvortex.com/showthread.php?5427024-Testing-Fuel-Pump-Problems-amp-Solutions-thread