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Help with rail pressure pre-start-up.

vwengineer

Ready to race!
Location
Switzerland
Yes, I saw a video where they diagnose it on an MK6. In the video they use an inline gauge probably because of this but you can also probably pull the fuse with ignition ON and VCDS running as you suggested.

In the video the pressure would drop quickly once ignition is switched off and replacing it fixed the long cranking issues.
 

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
Thank you for that...I just edited it to 40mA. I was just told this some hours ago....so they were off a bit.
I shouldn't have an issue with the battery...I believe it is less than a year old. But driving it two days ago, I expect it to be over 12v. It was probably 45° in the garage overnight and cold will lower voltage, yes?
 

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
Looks to be just 1/5 of a volt based on its SoC(state of charge)....and much less based on temps.
Cool, thanks again. I have about another hour before I check the parasitic drain. It was 1730mA (1.73A)...we'll see.

That was a waste of time...after 2.25 hours it still reads 1.73A. I just learned I need to latch the hood latch so it thinks it is closed. Going to try again tomorrow.
 
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ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
Yes the temp of the battery electrolyte will change the batteries State of charge(Soc), but that change is minimal. Take a look at this chart

http://wiki.orbswarm.com/images/e/e4/Pb_battery_state_of_charge.png

As you can see in the AGM/ Gel cell at 120°F Soc 12.813 & at 0°F Soc 12.666
OK...I've just gone out and opened the hood but set the hood latch back to its closed position. I checked the MFD to see if it registers as closed and it does. Then I see it stated elsewhere that you must establish a shunt in that you connect the meter leads to the battery cable and post while the cable is connected. Then you must disconnect the cable while keeping the leads attached to both the cable and post. That seems near impossible. I believe I am going to give up on this. It seems best to just skip a draw test at the battery and do as the Humble Mechanic does, going straight to checking each fuse with the battery connected and the door latches in their closed positions...after a go-to-sleep time.
 
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vwengineer

Ready to race!
Location
Switzerland
Then I see it stated elsewhere that you must establish a shunt in that you connect the meter leads to the battery cable and post while the cable is connected. Then you must disconnect the cable while keeping the leads attached to both the cable and post. That seems near impossible. I believe I am going to give up on this.
It's not necessary, just disconnect the battery and connect the multimeter in-between. Yes it will reset the car computers but it doesn't matter, the drain will settle fast to "sleep mode" once the car is locked with hood closed (did that already). Another way to do that is to connect and spare battery in the cigarette lighter while you do the connection, then remove the 2nd battery, then nothing is reset but you have to be very careful not to touch any ground with the positive lead.

If you want some measurements I did:

- Car locked after a few minutes, almost 0A
- Doors open with roof lights OFF but foot lights on, a bit more than 1A
- Ignition ON, engine OFF around 7A continuously
 

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
Everything I tried showed 1.73A. I kept finding more and more said to do in order to get an accurate reading. The last time I tried was; open the hood and reset the latch and make sure the MFD showed the hood shut, run the engine to make sure battery was not weak, shut it off, close the door and lock it. Then I waited over two hours. Did all of this twice plus...once not disconnecting the battery until I did the test and once disconnecting the battery at the start of the two hours and then testing it. Everything I did resulted in 1.73A...which is the same I see if I do nothing else except for disconnecting the battery and immediately check the draw. This is why I feel the only thing I can do now is just leave it all hooked up except reset the door latches. Wait for the time again and then check all of the fuses.

Just going to do this:
 

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI

GTI's

Drag Race Newbie
Location
MD
OK...I've just gone out and opened the hood but set the hood latch back to its closed position. I checked the MFD to see if it registers as closed and it does. Then I see it stated elsewhere that you must establish a shunt in that you connect the meter leads to the battery cable and post while the cable is connected. Then you must disconnect the cable while keeping the leads attached to both the cable and post. That seems near impossible. I believe I am going to give up on this. It seems best to just skip a draw test at the battery and do as the Humble Mechanic does, going straight to checking each fuse with the battery connected and the door latches in their closed positions...after a go-to-sleep time.
Take a couple of jumper wires that are of proper size with clamps and disconnect the negative cable, connect one end of the clamps to the end of the negative battery cable and the others to the negative battery post. Now wait till car goes to sleep then you can connect the meter leads to the end of the negative cable and post and remove the jumper clamps from the post and cable. Now you can read the meter. Want to give it more time and check it later reconnect the clamps to the post and cable then remove meter and repeat when you want to test again.
 
Last edited:

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
Thank you for the great idea. I will try this...I'm beginning to question my inexpensive meter now. But we'll see next time.

I just checked all of the fuses and saw nothing, but I couldn't test the smaller fuses in the upper two rows (rows 1 & 3...there are none in row two) as they do not have external access I've circled;
fuss.png
 

GTI's

Drag Race Newbie
Location
MD
Thank you for the great idea. I will try this...I'm beginning to question my inexpensive meter now. But we'll see next time.

I just checked all of the fuses and saw nothing, but I couldn't test the smaller fuses in the upper two rows (rows 1 & 3...there are none in row two) as they do not have external access I've circled;

If you can not find ones with access to replace yours people have taken a small drill bit and created access holes.
 
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