Intermittent hard start / long cranking when engine is warm

[Sprocket]

Hi everyone, I hope you're all doing well during these crazy times. I've had some extra time lately, so I've been trying to diagnose and repair a couple of small issues I'm having with my B5.5.

The issue I'm experiencing is intermittent hard start when the engine is warm. It always starts, but may crank longer, again only when the engine is warm.

Here is a VCDS scan and I'm leaning towards replacing the coolant temp sensor, but I'd like to get some feedback from you as well to confirm that I'm on the correct path.

I know the door lock module on the rear driver's side door needs to be replaced as well.

The no communication with the radio is due to an aftermarket head unit.

Can someone please explain to me what this fault is related to "Company Data Bus for Comfort System".

Address 01: Engine Labels: 038-906-016-BHW.lbl
Part No SW: 038 997 016 T HW: 028 101 198 2
Component: R4 2,0L EDC G000SG 0314
Revision: 12345678 Serial number: VWZ7Z0D0237910
Coding: 0150031
Shop #: WSC 66565 257 00032
VCID: 2F6DA95ABD1200FEAB-515E

1 Fault Found:
16512 - Coolant Thermostat Valve (N214)
P0128 - 000 - Temperature below Control Range
Freeze Frame:
RPM: 1848 /min
Torque: 112.0 Nm
Speed: 52.0 km/h
Temperature: 67.5°C
Fuel Consump.: 4.40 l/h
Temperature: 37.8°C
Temperature: 37.8°C
(no units): 1161.8

Readiness: 0 0 0 0 X

-------------------------------------------------------------------------------
Address 03: ABS Brakes Labels: 4B0-614-517.lbl
Part No: 4B0 614 517 G
Component: ABS/ESP front 3428
Coding: 04255
Shop #: WSC 05311
VCID: 25414B72BFEE4AAE51-5124

No fault code found.

-------------------------------------------------------------------------------
Address 15: Airbags Labels: 6Q0-909-605-VW5.lbl
Part No: 1C0 909 605 C
Component: 09 AIRBAG VW61 04 0003
Coding: 12345
Shop #: WSC 05311
VCID: 24475676B4D4B3A646-5124

No fault code found.

-------------------------------------------------------------------------------
Address 16: Steering wheel Labels: 1J0-907-487-A.lbl
Part No: 1J0 907 487 A
Component: Lenkradelektronik 0005
Coding: 00118
Shop #: WSC 05311
VCID: 2F6DA95AED1200FEAB-5140

No fault code found.

-------------------------------------------------------------------------------
Address 17: Instruments Labels: 3B0-920-xx5-17.lbl
Part No: 3B0 920 929 C
Component: KOMBI+WEGFAHRSP VDO V04
Coding: 13235
Shop #: WSC 00000
VCID: 275D417AC5E258BE63-5124
WVWAE63B75E037384 VWZ7Z0D0237910

3 Faults Found:
01039 - Coolant Temperature Sensor (G2)
30-10 - Open or Short to Plus - Intermittent
01336 - Company Data Bus for Comfort System
49-10 - No Communications - Intermittent
01304 - Radio
49-00 - No Communications

-------------------------------------------------------------------------------
Address 19: CAN Gateway Labels: 6N0-909-901-19.lbl
Part No: 6N0 909 901
Component: Gateway K<->CAN 0001
Coding: 00006
Shop #: WSC 05311
VCID: 70EF6A2630AC5F06F2-5140

2 Faults Found:
01336 - Company Data Bus for Comfort System
49-10 - No Communications - Intermittent
01304 - Radio
49-00 - No Communications

-------------------------------------------------------------------------------
Address 46: Central Conv. Labels: 1C0-959-799.lbl
Part No: 1C0 959 799 C
Component: 08 Komfortgerát HLO 0004
Coding: 00259
Shop #: WSC 05311
VCID: 377D913A1542C83EF3-4B02

Subsystem 1 - Part No: 1C1959801
Component: 08 Tõrsteuer.FS KLO 0202

Subsystem 2 - Part No: 1C1959802
Component: 08 Tõrsteuer.BF KLO 0202

Subsystem 3 - Part No: 1C0959811
Component: 08 Tõrsteuer.HL KLO 0202

Subsystem 4 - Part No: 1C0959812
Component: 08 Tõrsteuer.HR KLO 0202

1 Fault Found:
00930 - Locking Module for Central Locking; Rear Left (F222)
27-10 - Implausible Signal - Intermittent

End-------------------------(Elapsed Time: 04:42)--------------------------

 

[oilhammer]

Not sure about the data related DTC, may be due to the radio. The vehicle speed signal normally goes to the radio, that may be part of it?

I had a BHW that had a hard hot soak restart and it was the owner put WAYYYY too much anti-gel in the fuel. I know you would not have done that, however has this issue been happening over the course of a few tanks of fuel? That would at least rule out bad/wrong/contaminated fuel anyway.

Next thing I can think of is maybe check the fuel temp sensor value in the engine data and see if it corresponds with what it should be, or at least what you'd think it should be. Overnight cold start would obviously be equal to ambient, as well as coolant and intake air. After running for a while should be fairly close to coolant temp I'd think. At least look for something that is not totally off the wall, use your best judgement.

But yeah, replace that CTS anyway.

 

[ekkoh99]

here is a copy of my earlier post. i had hard starts in the AM and after the car was warmed up. intermittent. Much better now with new thermostatic T on top of the fuel filter.

my wagon in the last six months intermittently had a difficult start and then rough idle for 10 to 20 seconds then smooths out. sounds like misfiring but smooths outs quickly. doesnt happen all the time. glow plugs and software were done years ago too. happens in warm and cold weather. i was worried about the starter and battery but they check out ok. Any thoughts?

1. fuel injection quantity OK on VCDS. all similar +/-.45 to .9
2. resistance of lift pump 2.8
3. I hear the lift pump when i turn the key.
4. I change the fuel filter once a year.
5. Is the fuel check valve in the lift pump or the tee piece connector on the fuel filter top?
6. Torsion value at 0
7. No codes with VCDS

 

[Reichard]

After 15 years, my BHW Passat started with the won't start when hot BS. As soon as the car is up to temp, it will not restart. Had to wait at least 2hrs for a cooldown otherwise it'll just crank and crank til the warning comes up on the MFD.

After reading the 40+ page thread, I spent three weeks trying and trying to fix it. No codes were set at all. Measured cranking rpms 258. Torsion value -0.8.

What I changed:

Coolant temp sensor -- what a bugger to get at!

Fuel filter -- Filter was changed by local garage. Mann-brand installed but the o-rings on the thermostatic T weren't replaced. The blue o-ring was actually torn. Replaced filter and O-rings with a new Mann filter.

Tandem pump and associated vacuum lines and new coolant lines.

TDI hot start fix module from Poland. Lots of positive reviews. Splices inline with coolant temp sensor and battery. when key is turned to crank, ECU sees a resistor instead of CTS, thereby a low coolant temp is registered. More fuel and glow time for easier starting.

Unplugged cam position sensor when engine hot and tried starting but that didn't work.

Battery just replaced last winter with a new Duracell. Car cranks fast enough as vcds shows and batt voltage good while cranking

Had 8gal in the tank of diesel. Added 8oz Diesel Kleen.

Massive frustration at this point. Yesterday, I siphoned all the fuel out of the tank to prepare for lift pump removal. There was about a tablespoon of water in the fuel. Fuel looked straw yellow but I just figured it was from the additive.

Today I planned on removing the lift pump and clean the pickup screen, and removing the ECU to send to Jeff and Rocketchip for the hot-start flash fix. Car had RC2 previously. Car sat all night, and started up fine this morn as usual. My father drove it to the Sunoco and added 5g to it while running. Drove to the dollar store and accidentally shut it off instead of leaving it running. It immediately restarted! Drove home, we waited 20min, and tried starting, expecting it to just crank and crank, but it easily fired over.

Again, test drive for several miles, drive home, let it sit 30min, and it restarted.

So, I'm chalking this one up to bad fuel and perhaps the fuel filter. Glad it wasn't the starter or lift pump.

I'm still going to send the ECU to Jeff just for peace of mind. Thanks to the community for all the resources here!

 

[ekkoh99]

I was going to change the lift pump but I changed the o rings on the thermostatic T which did not help. When I changed the thermostatic T on top of the fuel filter, the problem went away for now.

 

[dylphil97]

link to this part???

TDI hot start fix module from Poland. Lots of positive reviews. Splices inline with coolant temp sensor and battery. when key is turned to crank, ECU sees a resistor instead of CTS, thereby a low coolant temp is registered. More fuel and glow time for easier starting.

How much do you think this had to do with your success?




Thanks

 

[Sprocket]

Not sure about the data related DTC, may be due to the radio. The vehicle speed signal normally goes to the radio, that may be part of it?
I had a BHW that had a hard hot soak restart and it was the owner put WAYYYY too much anti-gel in the fuel. I know you would not have done that, however has this issue been happening over the course of a few tanks of fuel? That would at least rule out bad/wrong/contaminated fuel anyway.
Next thing I can think of is maybe check the fuel temp sensor value in the engine data and see if it corresponds with what it should be, or at least what you'd think it should be. Overnight cold start would obviously be equal to ambient, as well as coolant and intake air. After running for a while should be fairly close to coolant temp I'd think. At least look for something that is not totally off the wall, use your best judgement.
But yeah, replace that CTS anyway.

Thanks for the insight OH, I appreciate it. Yeah, this has been happening over a few tanks of fuel and I do use an anti gel in the colder months, but the correct dosage. I'll check out the suggestions as far as fuel temp, coolant, & air intake as well to make sure everything correlates correctly.

 

[Sprocket]

I was going to change the lift pump but I changed the o rings on the thermostatic T which did not help. When I changed the thermostatic T on top of the fuel filter, the problem went away for now.

I appreciate the response, but I have the CAT filter setup on my B5 and I have an open T, so this is not my issue.

https://kermatdi.com/i-443-kerma-widget-mk4-bhw.html

 

[Reichard]

How much do you think this had to do with your success?

The issue seems pervasive enough such that this device was designed and has fixed the issue for many. I'm installing a switch to defeat it in order to get a firm understanding of the situation.

I think the torn o-ring on the thermostatic Tee, along with some bad fuel were the culprits in my case.

 

[oilhammer]

I appreciate the response, but I have the CAT filter setup on my B5 and I have an open T, so this is not my issue.
https://kermatdi.com/i-443-kerma-widget-mk4-bhw.html

Oh, well that may be your problem. Every time I run across any TDI that has road grader parts on it and has some form of strange operation happening, I remove it, and it generally fixes it (which is why I have thrown stacks of these in the scrap bin). Although this would seem to not be the issue here, if the car starts normally after it has cooled down to ambient.

I am not aware of any hard start software fix for the BHW like the BEW has.

 

[Reichard]

I am not aware of any hard start software fix for the BHW like the BEW has.

I've read about copying the cold start tables onto and overwriting the hot start tables. Aren't the BHW and BEW similar enough that this would apply/help?

 

[oilhammer]

I've read about copying the cold start tables onto and overwriting the hot start tables. Aren't the BHW and BEW similar enough that this would apply/help?

I do not know. I just know that every BHW I have ever started, including my own, start faster than any other TDI. They are typically "running" after the very first compression stroke lights off. They don't really "crank" at all, hot or cold. BEWs (including both mine) always need at least a wee bit of cranking it seems. Maybe three or four cylinders' worth of compression strokes before they light off.

Probably why the starters never seem to wear out on them.

 

[Sprocket]

Oh, well that may be your problem. Every time I run across any TDI that has road grader parts on it and has some form of strange operation happening, I remove it, and it generally fixes it (which is why I have thrown stacks of these in the scrap bin). Although this would seem to not be the issue here, if the car starts normally after it has cooled down to ambient.

Yes, I know you're not a fan of these . While I haven't logged the data yet, I was driving and watched my temp gauge go from 190 down to 0 and then back up to 190, so I'm thinking I definitely have a bad CTS.