Low Fuel Pressure in Fuel Rail Issue. VCDS Block 20

[slevesque]

Hi everyone,

I’m experiencing an issue with my 2010 Golf TDI 2.0. I’m getting a low fuel pressure reading in the fuel rail and the code P087. The car starts and idles normally, but it goes into limp mode at higher RPMs. I’ve logged the data from Block 20 on VCDS, and I’ve noticed that the fuel pressure doesn’t exceed 770 bars.

I’ve removed the control valve from the HPFP and didn’t find any metal debris, nor was there anything unusual in the fuel filter canister. As mentioned, the car runs fine at idle, so the issue only seems to appear at higher RPMs.

At this point, I suspect the problem could be either the fuel pressure control valve on the HPFP or the one in the fuel rail.

Previously, I had a similar issue at higher RPMs when I gave full throttle. At that time, I had already replaced the fuel pressure control valve in the fuel rail. I decided to remove and inspect it, then reinstalled it. Since doing that, the issue occurs now at around 1500 RPM.

Could it be possible that the O-ring is damaged, preventing the fuel pressure from exceeding 770 bars? I’ve already ordered a replacement O-ring and plan to change it to see if it resolves the issue.

I don’t believe the problem lies with the injectors, as the car runs well at idle. I’ve attached a link to the graph from two tests I conducted in Block 20.

http://imgur.com/dSAAChp

http://imgur.com/4VPC0fg

Is there any way that I could be sure it's either the control valve from the HPFP or the one on the fuel rail?<

Any insights or suggestions would be greatly appreciated!

Thanks in advance for your help.

 

[Dannyboy]

Double check the auxiliary fuel pump is working correctly and flowing enough. Right in-between the coolant tank and timing belt cover.
They are known to go bad and starve the hpfp/rail of pressure.

 

[slevesque]

I have check the auxiliary pump and it looks like flowing plenty to me. I guess I can put a gauge and see the pressure if it's enough, but it looks like flowing enough to me. I have also check the pump from the fuel tank and looks good.

 

[GBaugh]

The pressure regulating valve on the rail is normally open to return when deenergized according to VW self study program SSP 826803 and SSP 403. This means it needs pwr and a sufficiently strong magnetic field to close and build psi in rail. A weak solenoid magnetic field could cause problems. I don't know what diagnostic tooling you have available but if you have a labscope you could look at slope of current ramps at pressure regulating valve solenoid on rail. Current ramps for a shorted solenoid with weak magnetic field will be more vertical due to low counter EMF. The current rise of each PWM current pulse in a healthy solenoid coil will exhibit a more gradual on-time current rise slope due to the stronger magnetic field and thus stronger CEMF that opposes the rise in current. Beauty of the labscope approach if you can find a tech nearby that has one, is that it's quick easy and noninvasive.

If no labscope, then maybe you could test for a magnetic field strength with screwdriver on back of solenoid at your problem rpm.

The fuel metering solenoid on the pump is normally open to psi chamber in pump when deenergized and fuel is routed to return as pwm pwr is applied so failure mode with weak solenoid is more likely to cause increase in fuel rail psi.

You may already be aware of this but there is TSB 01-10-11 for P087 with the 2010 Golfs basically pertaining to fuel contamination including water in fuel. As the vehicle owner you are in better position to determine if date, VIN and details of TSB apply to you.

Whenever dealing with fuel rail psi issues, I always like to verify fuel supply psi and flow as someone already suggested.

I see Ross Tech has a page on the P087 fault and they list fuel injectors as possible cause. Might be worth considering a fuel inj return flow leak off test. Even though your problem is at 1500 rpm, the return flow leakoff measurement at idle might reveal a problem.