Poor starting

[Scottb12345]

Hi all, after some technical advice please. 2017 vw transporter. CXEB. Problems starting when left for 5 mins or more. Hooked up a fuel pressure gauge on the low pressure pipe to the pump. It cranks for ages but eventually starts when the pressure hits 1 bar. Have done a leak off test on the injectors and they are all OK. Fuel filter changed also as a precaution. Have replaced the fuel pump pressure regulator too. Visual inspection of all fuel pipes and no visible leaks.

In addition if you clamp the return hose from the fuel pump you can leave as long as you like then remove the clamp and it will start straight away.

It seems that the fuel is running back to the in tank pump. But I can't figure out why. Only done 16000 miles!

Any help would be greatly appreciated

 

[Dellmassive]

You need to get the fuel rail pressure reading. Data from VCDS.

Leaking injector/?

Dirty injector/s?

Low battery power?

Air flow, MAP sensor?


There is a thread on here showing known good start/shutdown rail pressure readings.

 

[Scottb12345]

0 rail pressure before start, 300 when running. As mentioned done a leak off on the injectors all ok. Battery charge is fine, have also charged overnight to make sure. Won't be air flow or map i don't think. As mentioned as soon as the LP side hits 1 bar it's starts and runs perfectly. As soon as it drops below 1 bar it won't start unless you crank for ages to build the pressure back up

 

[Dellmassive]

Some more info here.

Post in thread 'Start up fault'

11 Mar 2022

@mmi

start-up rail pressure build.

@850rmp Rail pressure @ 27700kPa

• Dellmassive

• 

.

 

[Dellmassive]

4-cylinder common rail engine CXEB CXFA CXGA CXGB CXHA CXGC CXHB

5 Feb 2023

CXEB CXFA CXGA CXGB CXHA CXGC CXHB

• Loz
• cxeb engine cxfa engine cxga engine cxgb engine cxgc engine cxha engine cxhb engine manual
• VW Manuals

 

[Dellmassive]

Low cylinder compression?

What's the oil usage?

Can you get an in-cylinder pressure reading via glow plug holes?

Thread '- 204ps Bi-Turbo CXEB T6 Engine & Turbo problems -'

17 Aug 2024

- 204ps Bi-Turbo CXEB T6 Engine & Turbo problems -

Looks like im the latest patient of the CEXB engine issues.

(possibly the 2016-2018 range as there is a mention that the CXEB Block etc was revised in 2019)

(the CXEC 199ps Bi-Turbo was released 2019> and revised )

in sort it looks like its either Turbo or Engine failure.

here is some background:

******************************************************************
204ps Bi-Turbo CXEB Engine & Turbo problems...

• Dellmassive
• cxeb engine
• Replies: 494
• Forum: Engine, Gearbox, Exhaust, Drivetrain

• 
• 

.

 

[Dellmassive]

Did you say at the top it's only done 16,000 miles from new?

on a 2017 model?

 

[mmi]

Hooked up a fuel pressure gauge on the low pressure pipe to the pump. It cranks for ages but eventually starts when the pressure hits 1 bar.

Does the fuel transfer pump in the tank run at all?
Could run a simple test just to hear the pump whining - without cranking.

Thread '[T6_measured] 01-Engine - Built-in test for Transfer fuel pump'

15 Jun 2023

A quick DIY way to test fuel lift pump's basic functionality.

The test takes advantage of engine's fuel high pressure sensor (in fuel rail). Running the lift pump continuosly makes the pressure eventually "leak" through high pressure pump and can be detected by fuel pressure sensor.

As a side product the test gives at least indication of fuel high pressure sensor's plausibility - the raw value (in Volts) and converted value (in kPa). However, as the pressure produced by lift pump barely reaches measurement range - for proper pressure measurement traditional means are still needed...

• mmi
• fuel pump lift pump t6_measured vcds
• Replies: 8
• Forum: Engine, Gearbox, Exhaust, Drivetrain

• 
• 

 

[Scottb12345]

Did you say at the top it's only done 16,000 miles from new?

on a 2017 model?

Yes 16000 miles. No excessive oil usage. Cut open the old fuel filter no metal. If i clamp the hpfp return pipe (see image ) it will start everytime on the dot

 

[Dellmassive]

this:

https://www.t6forum.com/threads/vw-vag-ssp-self-study-programs.11179/

shows this:






.




.





.

is it possible that the N276 "pressure regulating valve" is not holding back pressure? - and leaking pressurised fuel back to the tank?


++++++++

come join up as VIP and have access to all the documents. - VIP Membership





.

 

[Scottb12345]

Ok so an update incase it helps any one. Had access to an identical vehicle today so added the fuel pressure gauge to the low pressure feed to the hpfp again. Again after starting the fuel pressure dropped away quickly BUT the rate in which in increased was far superior. Have ordered a new tank unit!

 

[Dellmassive]

nice keep us posted.