Starter solenoid noise, VW Golf Mk.6

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Starter solenoid noise, VW Golf Mk.6

Postby Valhalla » Wed Mar 04, 2015 11:04 pm

I am investigating an occasional non-start issue on a VW Golf Mk.6, the engine code is CGGA which is the gasoline 1.4 petrol, no turbo, with 59kW nominal rating. The battery is coming in for some suspicion, but this diagnostic has been a difficult one to call, as the engine turns over fine, and (for me, at least) it has never failed to start.

Before I try a new, bigger, battery on this car (I'm concerned about the voltage pull-down at the battery terminals themselves), I am trying to eliminate one feature of the starter-motor current/voltage traces that bothers me;

As shown on the attached trace, which has starter current draw measured on a clamp at the starter battery +ve feed wire near the solenoid, not only does the voltage at the motor fluctuate at soloenoid pre-engagement (or thereabouts), but I see a corresponding pull-up of the engine earth (the light-brown trace) and the battery terminals as well. All of the voltage traces are referenced back to battery -ve, and to be sure I have all the cable black plugs secured together at the battery -ve post. I can only find one other waveform on iATN that resembles this bahaviour, and that was a Honda of late-2000's model. Otherwise, I have no idea whether this "buzzing" of the solenoid current draw is normal for a VW of this type of platform, and whether I should be looking more closely at the starter relay and associated circuits. I have already dealt with the main power distributions on this car, and it is running an extra battery -ve lead directly to the starter motor ground cable post on the body (to bypass the VW design with all the starter current drawing through the inner wheelarch).

Has anyone seen this before, and is it worth worrying about? Many thanks for any help any of yourselves can give.


ADMIN: File removed see post below
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Re: Starter solenoid noise, VW Golf Mk.6

Postby Robski » Thu Mar 05, 2015 9:08 am

started looking at the capture.............. Pico crashed ( waste of time saying anything as being on WIN XP,on this PC, it will no doubt be my PC as always...) .......got bored of Pico software..............never bothered opening again.......... BUT....

from what I saw, nearly 600A cranking on a petrol(can't see rest of cranking current as your capture is too short, so have to go on what can be seen)......really ?.... & you wonder why you have such VD on the ground ?

Whats the engine like to turn by hand cold ?

Treat the starter & solenoid as one, what now ?

With the starter out of the equation & simulated load across the battery at 1/2 CCA what's the result ?
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Re: Starter solenoid noise, VW Golf Mk.6

Postby Martyn » Thu Mar 05, 2015 1:01 pm

We have looked at the data file, it is corrupt, and as such will not load successfully in to PicoScope so we have removed it to prevent any issues.

Can you re post the file, but without any zoom.

Thank you
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Re: Starter solenoid noise, VW Golf Mk.6

Postby Valhalla » Fri Mar 06, 2015 12:03 am


Sorry about the problem with the original posted file. Strange thing is, until I updated Pico Automotive s/w to latest version, I had no issues inthis respect, but have found now that anything that has a zoomed component (and the options set to "Save just zoomed ....") is also corrupt when I try to open it off my storage device, so that's a bit of nuisance....

I have reattached the unzoomed file here, and hope it doesn't chew too much bandwidth. That's why I just posted zoomed!

Robski, thanks for the feedback, I'll try to respond as best I can below, and come back tomorrow with the rest;
1) No it's not your computer, the s/w is up the spout again. As it happens, the Pico Diagnostic s/w neatly lost me my first test the previous day (exactly same hook-up, rubbish results), hence I've gone back to a manual analysis, so we are all having s/w issues.....
2) Yes, I'm a bit concerned about the 580A current once the motor is turning.
3) The VD at the ground is poor around this "strange" spiking area (which is the reason I zoomed into it), but you should now be able to see that the VD's around the starter ground and battery +ve cable to the solenoid are not too bad under normal cranking conditions. I could get them better (indeed, they are better than they were, after the work I did on the power distr around the battery and fusebox)
4) What also stands out is that the battery droops to 12.1v or thereabouts under pre-crank ignition loads. That is from a stable (removed surface charge) condition of 12.74v - not good. The car puts its lights into "daylight running" as soon as the key goes to pos_2, but I'm hoping to get a good current clamp reading on that and everything else from the starter itself, to see whether the battery is actually U/S. Hopefully this will give me a clue as to a "simulated load" re-measure on the battery.
5) I'm sourcing a new starter solenoid feed relay as I write this. I want to substitute this bit of the starter circuit and re-measure the "spiking" before the cranking occurs. After that, I think that the motor assembly is going to have to come off the car for a bench-test and re-scope away from the car, to get a better picture. The main concern I have is that I don't want to spend someone's money on a new battery if it isn't going to fix their problem. I have the original motor assembly from this car - swapped out last year for a suspected solenoid sticking problem - which I can rebuild onto the car for another measure. Given that I'm seeing a load of spiking on starter engagement, I need to eliminate that from the original diagnosis on the original motor last Spring.
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Re: Starter solenoid noise, VW Golf Mk.6

Postby AWright » Fri Mar 06, 2015 9:53 am

As shown on the attached trace, which has starter current draw measured on a clamp at the starter battery +ve feed wire near the solenoid, not only


Hi Vahalla, how close do you have the current clamp to the starter motor, is it possible the high current loads/magnetic fields are interfering with the clamps circuitry somewhat ?

Can you scope voltage of switched side of solenoid ? It may provide some clues to its condition
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Re: Starter solenoid noise, VW Golf Mk.6

Postby sigoaprendiendo » Fri Mar 06, 2015 11:39 pm

Here you are an analog very interesting case of study

https://www.picoauto.com/tutorials/ferrari360-diagnostics.html
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Re: Starter solenoid noise, VW Golf Mk.6

Postby Valhalla » Sat Mar 07, 2015 12:15 am

AWright wrote:
As shown on the attached trace, which has starter current draw measured on a clamp at the starter battery +ve feed wire near the solenoid, not only


Hi Vahalla, how close do you have the current clamp to the starter motor, is it possible the high current loads/magnetic fields are interfering with the clamps circuitry somewhat ?

Can you scope voltage of switched side of solenoid ? It may provide some clues to its condition


Thanks for the suggestions. I have a new relay on order as well, so I hope to do a "before" and "after" on the switched side. I was having the very same thought last night that the switched-side might reveal what is going on!

As for the 600A clamp, yes, it's right up against the back of the starter, within 10cm of the starter solenoid +ve stud. I did move it away slightly between tests across two days, and it didn't make much difference. What made me think that induced signals were not being recorded straight off the starter windings or solenoid windings, was that the voltages 0.5m away at the battery were sympathetic to the current clamp. Unless there is a chance that the measurement leads are somehow dragging the battery -ve reference to make me think that the deltas are there at higher current readings.

Anyway, it's a good suggestion to try the current clamp much further away from the motor, then see what is revealed.
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Re: Starter solenoid noise, VW Golf Mk.6

Postby Valhalla » Sat Mar 07, 2015 12:25 am

sigoaprendiendo wrote:Here you are an analog very interesting case of study

https://www.picoauto.com/tutorials/ferrari360-diagnostics.html


Many thanks for this. I believe that this is the direction I am going in, so a useful case study like this one is great. In particular, I suspect starter solenoid "chatter" to have been responsible previously for a "grating" noise on crank, previously reported by the customer last year. This was addressed at the time by fitting a new starter motor assembly, but that may have just hidden the symptoms of the problem - possibly in the solenoid supply circuits.
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Re: Starter solenoid noise, VW Golf Mk.6

Postby Valhalla » Sat Mar 07, 2015 12:29 am

[quote="Robski"

Whats the engine like to turn by hand cold ?

[/quote]

It appears that the engine is not unusually stiff to turn from the auxilairy drive end of the engine. So where the 580A is coming from is a mystery - looks like a very inefficient starter motor. I'm going to see if I can set the tripod up for the next indoor test on this car. I hope to get a temperature measure off the casing before and after cranking, just to see if the battery energy is disappearing as heating. I have a rough mass of the motor from the shipping weight on this unit when it was supplied last year.
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Re: Starter solenoid noise, VW Golf Mk.6

Postby Valhalla » Wed Mar 11, 2015 11:11 pm

A slight update on the tests (the car has been left with me for a longer-term trial, so I'm fitting it inbetween other work);

I re-measured the starter current with the clamp on the same cable, but at the battery end i.e. away from the starter. Exactly the same electrical disturbance as the solenoid is operated.

The same test as above also substituted the engine ground measure for a voltage trace on the solenoid actuator. A similar disturbance in the voltage level as the main battery voltage, and the starter lead voltage, could be seen at the solenoid actuation, but stranger still is that it doesn't quite follow the pattern, and following starter motor switch-off there is a decaying voltage for approximately 1second before complete shut-off to 0v. So I'm definitely going to try the new starter relay, plus measures around this, before condemning anything else. If this "decaying voltage" pattern is typical of VW's, then it might explain why so many of their products have post-start starter motor hang-up whining problems.
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