3.0tdi Slow to start in the mornings

[Dane]

Evening gents,

The allroad is still struggling to start in the morning, it's cranks but doesn't fire for 10 seconds ish.

I've had the battery changed and the glow plugs changed so far, I've been reading up on the inter webs and there seems to be mention of fuel pressure needing to be at 10 psi and there's a valve that commonly looses pressure over time, any one know anymore about this / want to suggest things to explore.

No relevant fault codes start from either.

 

[B5NUT]

Only things I can think of are fueling or injectors. I take it you have no issues when the engine is hot?

 

[Dane]

No issues starting the engine at any other point, and no driving issues either, no stuttering or holding back.

I think it's had injector work in the past IIRC but I'll check the receipts.

It seems to be a fairly common issue with no clear cut solution, a new starter motor seems to have worked in some cases though

 

[Ginge247]

Evening gents,

The allroad is still struggling to start in the morning, it's cranks but doesn't fire for 10 seconds ish.

I've had the battery changed and the glow plugs changed so far, I've been reading up on the inter webs and there seems to be mention of fuel pressure needing to be at 10 psi and there's a valve that commonly looses pressure over time, any one know anymore about this / want to suggest things to explore.

No relevant fault codes start from either.

I don't know if you sorted it yet m8 but I have a the same problem, very intermittent though. I found this
http://workshop-manuals.com/audi/a5...nstalling_fuel_pressure_regulating_valven276/
I haven't done anything about it yet though.

 

[gupsterg]

I've been reading up on the inter webs and there seems to be mention of fuel pressure needing to be at 10 psi and there's a valve that commonly looses pressure over time, any one know anymore about this / want to suggest things to explore.

This thread has some info about it, Link:- http://www.vwaudiforum.co.uk/forum/...had-faults-with-the-V6-TDi-fuel-return-system

Post 9 of above linked thread have test method.

Post 3 has some info on the other valves/sensors on common rail, if you had issues with any of those valves I'd think you'd get a DTC excluding the injector return pressure valve as that has no elec.connections. If that was faulty I'd think you'd have other issues than just slow cold start.

N276, N290 can be actuated by a VCDS output test in engine ECU plus you can check MVB's:-

022 Rail pressure control

  1) Engine speed

  At idle: 720 ... 820 rpm

  2) Specified rail pressure

  [bar]

  3) Rail pressure actual

  [bar]

  4) Pressure regulating valve activation

At idle: 15 ... 30 %

  - Values for warmed-up engine

  - Permissible difference between specified and actual value at Idle: maximum +-20 bar


023 Rail quantity control

  1) Engine speed

  At idle: 720 ... 820 rpm

  2) Specified rail pressure

  Check values with measured value block 022

  3) Rail pressure actual

  Check values with measured value block 022

  4) Quantity adjuster valve activation

At idle: 35 ... 48 %

  Values for warmed-up engine

I think above tests would also give you an idea if G247 is ok.

I gotta admit at times thought mine was a bit slow on cold starts and I'd gone through process of new glow plugs / injectors / battery and other bits as I'd had other issues and when my starter motor did conk out that was the biggest improvement for starting. Perhaps observing MVB data for cranking speed and comparison with another will show if starter motor weak?

 

[desertstorm]

I don't know if you sorted it yet m8 but I have a the same problem, very intermittent though. I found this
http://workshop-manuals.com/audi/a5...nstalling_fuel_pressure_regulating_valven276/
I haven't done anything about it yet though.

I think the reference to the 10 PSI is possibly related to the restrictor on the return flow from the injectors. Item 9 on the diagram.

http://workshop-manuals.com/audi/a5...ion_system_diesel_injection/injection_system/

This actually works at 10 bar (145 PSI) page 40 in this document

http://vwts.ru/engine/cata/pps_941803_3l_tdi_cata_w_clean_diesel_system_eng.pdf

Karl.