Mysterious Starting Problem

[Great Lakes TDI]

I have a 2015 Passat TDI SE 6MT. It has 15,000 miles and one prior owner to me.

The car is great...except for a mysterious, intermittent starting problem.

Once in awhile the car will not start and tells me to depress the clutch pedal. Obviously the clutch pedal is fully depressed when this happens. I don't get any error codes.

I either have to pump the clutch pedal repeatedly with the ignition in start or wait 15-20 minutes in order to be able to start the car.

Highly frustrating as you can imagine!

Thinking it was an issue with the clutch pedal safety sensor, I ordered
1K0 927 810 D. However, according to my research this sensor is connected to the CANBUS and there should be some kind of error message if it is not functioning correctly.

I have an appointment at the mechanic tomorrow to swap this part.

Am I on the right track, or does someone have a better idea?

 

[thundershorts]

Battery age/condition/voltage could affect it as it does everything else.

 

[JohnTso]

I agree! These cars need a fully charged battery to operate properly.

 

[Great Lakes TDI]

Replacing 1K0 927 810 D did not solve the issue.

Picked the car up today, went to the grocery store, then came back to work to wrap things up.

Tried to leave just now, and the car wouldn't start. Exact same issue.

Battery has 92% of its original charge voltage, which sounds good but I realize isn't. I suppose I'll try replacing the battery next. I need an oil change soon, plus I ordered a Frost Heater which I'd like installed.

 

[thundershorts]

VW seems to use Exide built batteries which are built close to what Varta standards were.
I'd try to avoid calcium ones such as you would find at big box retailers. It makes sense to buy the best as it will last longer and avoid a lot of problems. Actually when the dealers have a promotion going, price from dealers is very competitive.

 

[Great Lakes TDI]

I intend to get a "premium" AGM (better for cold weather) battery with the largest capacity that is compatible with the vehicle.

Even if this doesn't fix my problem (I'm skeptical) it doesn't hurt.

 

[Jetta_Pilot]

I intend to get a "premium" AGM (better for cold weather) battery with the largest capacity that is compatible with the vehicle. Even if this doesn't fix my problem (I'm skeptical) it doesn't hurt.

This is the battery I put into my 2015Passat but it took me about 3 hours to make it fit. The tray the battery sits on had to be removed and cut/sawn to make the battery fit.
The original cables still fit.



This Autozone Duralast Platinum has much more capacity than the OEM and more CCA too.

You need to set the computer with a VCDS to AGM to allow for a different charging rate for an AGM battery.

 

[Great Lakes TDI]

This is the battery I put into my 2015Passat but it took me about 3 hours to make it fit. The tray the battery sits on had to be removed and cut/sawn to make the battery fit.
The original cables still fit.



This Autozone Duralast Platinum has much more capacity than the OEM and more CCA too.

You need to set the computer with a VCDS to AGM to allow for a different charging rate for an AGM battery.

Thanks. I looked at this, but there is no Autozone where I live. The car battery industry appears to be stuck in the past with its dealer-centric distribution model.

There is an O'Reilly's which offers a comparable Group 49 AGM battery: https://www.oreillyauto.com/detail/...-group-size-49-top-post-battery/49plt/4742701

Consumer Reports evaluated a Group 65 Super Start AGM battery positively, so it should be good.

Odyssey is another option and actually ships, but it's not from their extreme series so I don't see much benefit to paying the Odyssey surcharge.

 

[Jetta_Pilot]

Great Lakes TDI
The O'Reilly looks to be very similar.

The Autozone cost me $ 194.00 plus core charge, which I was not able to get back. Long story !!!

 

[Great Lakes TDI]

Replacing the battery appears to have solved the issue

Weird, but I'm relieved

I'll follow up with you guys in a week

 

[tdiatlast]

Hopefully your starting problem is solved. Weird electrical anomalies are legendary across all vehicles these days, and the best place to start is with the 12V battery.

VAG cars aren't the only ones with 12V battery issues causing bizarre, seemingly unrelated problems. Our 2013 CMax (excellent car, by the way, nearing 100k miles, averaging 39mpg), even after mulitple software updates, can pull the battery down in a heartbeat, without warning, for unknown reasons. I routinely overnight charge it with a BatteryTenderPlus every 3-4 weeks.

I've been putting each of my cars on a BatteryTenderPlus every 3-4 weeks for the past 10 years. Seems ridiculous that the MORE sophisticated/complex our cars have become, their electrical systems aren't able to keep up and batteries can fail w/o warning.

 

[Jetta_Pilot]

I would suggest the problem is that there are too many things in todays cars which need 12volt to keep them going even when the engine is shut off.

For instance alarm systems are one.


So maybe the car manufacturer installing the least expensive barely capable battery might be at fault.

 

[oilhammer]

There are also countless wireless things that the car "detects" and even though it "ignores" them, the fact that it is detecting and thinking and going through the [electronic] motions to ignore them all uses electricity.

We had a lab scope on the BEAN bus (funny name, but in Toyotaspeak it stands for Body Entertainment Area Network, something stacked ON TOP OF the CAN bus) in an SC430 at school and you could trigger some action by simply pressing a key fob... from anything... even a non-Toyota product.

So imagine if your car is parked within the operational range of a key fob (like in a parking lot) and it is constantly having to reconcile the signal as valid or not.

It is made even worse today with all the satellite and smart phone nonsense they are straddled with. GM cars are constantly uploading info via Onstar. Which is why you can get an email or phone call from them to inform you your battery is getting weak.... ironic.

 

[Great Lakes TDI]

I may have celebrated too soon and jinxed it.

Problem is back.

Any other ideas gents?

New starter? Contact VW (car is CPO)?

 

[crdouger]

Great Lakes TDI, Any update? My 13 passat hasn't started twice now...just clicks...and I get some random lights on the dash. Both times it started about 30 minutes later. I was thinking battery, because I'm not sure the battery is the right one. It's putting out 11.8volts and I don't see any drop when the key turns and I hear a click, but nothing else. You gave me hope it was the battery, but now I'm not sure.

 

[Vince Waldon]

11.8 volts means your battery is very discharged... should be around 12.5 after sitting a while.

Since you have a voltmeter, once you get your car started again (a boost should do it) see if the voltage jumps to at least 13.5. If not, there's an issue with your charging system first and foremost.

Won't be the batteries fault if the charging system is not working, and with your meter you should be able to narrow down which expensive part to replace.

 

[Great Lakes TDI]

Great Lakes TDI, Any update? My 13 passat hasn't started twice now...just clicks...and I get some random lights on the dash. Both times it started about 30 minutes later. I was thinking battery, because I'm not sure the battery is the right one. It's putting out 11.8volts and I don't see any drop when the key turns and I hear a click, but nothing else. You gave me hope it was the battery, but now I'm not sure.

Yes, I have an update, and not a happy one.

Replacing the battery did not solve the issue, though initially I thought it did.

The nature of my starting problem, which is different from yours, is that the vehicle especially will have trouble restarting immediately after the engine has been running. After waiting 15-20 minutes the car will start...

...except when it's hot out, and the car has been parked in direct sun for awhile.

Then it won't start AT ALL.

It's necessary to wait for things to cool off and open the hood.

So far I've tried:

• Clutch pedal sensor replacement
• Battery replacement
• Starter replacement

Same problem.

All I know is there's some kind of mysterious thermal issue.

I just had to abandon my car at the hardware store and have someone come pick me up.

At this rate I'm going to need to buy another car. It will be a major loss as I can't ethically sell this vehicle to anyone else either.

 

[740GLE]

I'm impressed you've lived with it for 8+ months now.

I know some aftermarket remote start kits have clutch switch disabled option. I wonder if something like that could be accommodated, or possibly even coded into the ECU/BCM.

Granted it'd allow you to start the car while in gear with your foot off the clutch, but sure better than a non start car.

 

[Fixmy59bug]

Yes, I have an update, and not a happy one.
Replacing the battery did not solve the issue, though initially I thought it did.
The nature of my starting problem, which is different from yours, is that the vehicle especially will have trouble restarting immediately after the engine has been running. After waiting 15-20 minutes the car will start...
...except when it's hot out, and the car has been parked in direct sun for awhile.
Then it won't start AT ALL.
It's necessary to wait for things to cool off and open the hood.
So far I've tried:

• Clutch pedal sensor replacement
• Battery replacement
• Starter replacement

Same problem.
All I know is there's some kind of mysterious thermal issue.
I just had to abandon my car at the hardware store and have someone come pick me up.
At this rate I'm going to need to buy another car. It will be a major loss as I can't ethically sell this vehicle to anyone else either.

You say the car is CPO. Why wouldnt you let them take a stab at it?

If you know the circumstances you should be able to easily reproduce the problem in front of them. If you show them what it is doing and when they can see it, they cant say "No Problem Found"

 

[Great Lakes TDI]

You say the car is CPO. Why wouldnt you let them take a stab at it?
If you know the circumstances you should be able to easily reproduce the problem in front of them. If you show them what it is doing and when they can see it, they cant say "No Problem Found"

Was unable to reproduce the issue when I went to the dealer last fall.

However, now that it's summer time, it should be easy enough to reproduce the issue.

 

[Great Lakes TDI]

Starting to think it's the fuel pump. Heat-related starting failures seem to involve fuel pumps from time to time according to my research, and as I was just trying (and failing) to start my car I noticed every time I turned the key there was a sound coming from BEHIND me.

Perhaps the sound of the car trying, and failing, to engage the fuel pump?

 

[jw4free]

I am imagining back to gasoline carb days.

My thought was vapor lock, but that may not be a real thing with direct injected Diesels.

And you could still crank them until the battery died.

 

[pedroYUL]

Starting to think it's the fuel pump. Heat-related starting failures seem to involve fuel pumps from time to time according to my research, and as I was just trying (and failing) to start my car I noticed every time I turned the key there was a sound coming from BEHIND me.

Perhaps the sound of the car trying, and failing, to engage the fuel pump?

Your car has a lift fuel pump in the tank, and a high pressure fuel pump in the engine compartment (timing belt driven).

I read that if either fail to raise the rail pressure to the expected value, it will trigger a code. I believe you say there is no codes.

My 2015 Passat sometimes won't restart right away too, but my case is different. If the my car dies (kid is learning to drive), it won't restart unless the key is taken out, reinserted, and the clutch is cycled. I'm not sure which is fundamental, cycle the clutch or getting the key completely out, but if you do both it works. It doesn't bother me, so I haven't research this problem. No codes in my case.

 

[berks_tom]

My vote would be for the fuel pump. I have a family member with an older (2001) diesel pickup. The electronic fuel pump had an issue where the truck would not start when hot. After it cooled down it was fine. On one occasion we used a leaf blower and a bag of ice to cool down the fuel pump so the truck would start.

 

[thundershorts]

In tank pump gets my vote, if no low pressure code possible pressure sensor is faulty? The pump is a warranty covered item but its got to show failure at dealer for them to replace it as itself has no sensor to throw code. When mine failed, I ended replacing it myself to avoid the possibility of getting stuck somewhere.