Fuel Rail Pressure Too Low-Tested Injectors

[passdattdi]

Thanks for the breakdown and advice. Definitely helps.

Did swaping out the head on hpfp solve low fuel pressure?

I actually did replace the whole pump in case of worn piston or other internal parts. Initially I did shop the wrong pump based on car year, make, model. Car didnt wven start. As you stated, much more complex than that. So i decided to get exact match; everything. Slapped it on, started right away. Unfortunately, did not solve issue though. At any rate, before looking into pump again, I'll start again with other things

If one follows the manual , says don't replace pump if no metal. I don't have metal so will approach differently. At the moment, we will be looking into fuel injectors. Bought a kit to test return rate. Seems the number 4 is returning about q0 ml more than the rest. Will look into it further.

I agree, only so many things that can affect that pressure. Just the fact that I can name all those components off top of my head tells you how much I been researching and working on this, lol.

 

[Dr Sheldon]

Blind leading the blind !

Sad to see

 

[jackofromtheuk]

Blind leading the blind !

Sad to see

Excuse me !!
Please !!

Politely, if you don't have anything helpful to add, then spare us all. I'm not frequently on this forum but your posts come up quite a lot, and are almost always condescending, frequently unhelpful and often just wrong. If you find something I posted is incorrect then by all means explain why you think that for the benefit of us all, but off the cuff remarks like that help no one.

If you're postulating (but didn't ask) why I have so many spare parts it's because I had my HPFP grenaded 7 years ago (yes, the follower got eaten by the cam lobe and I had swarf throughout the whole lot) so replaced the entire fuel system bar the tank and tank lines. I just kept them in my special shelf of expired car parts. Oh, and except for the occasional issue with this check valve it's done 2 more timing belts and 70,000 more miles with my hands, so I'm certainly not "blind".

Thanks for the breakdown and advice. Definitely helps.

Did swaping out the head on hpfp solve low fuel pressure?

I actually did replace the whole pump in case of worn piston or other internal parts. Initially I did shop the wrong pump based on car year, make, model. Car didnt wven start. As you stated, much more complex than that. So i decided to get exact match; everything. Slapped it on, started right away. Unfortunately, did not solve issue though. At any rate, before looking into pump again, I'll start again with other things

If one follows the manual , says don't replace pump if no metal. I don't have metal so will approach differently. At the moment, we will be looking into fuel injectors. Bought a kit to test return rate. Seems the number 4 is returning about q0 ml more than the rest. Will look into it further.

I agree, only so many things that can affect that pressure. Just the fact that I can name all those components off top of my head tells you how much I been researching and working on this, lol.

Swapping the head fixed my latest issue, but I was 99.9% sure within the first 30 minutes it was the HPFP check valve as I've been there before, and the symptoms were identical. I was quite confused as no end of inspection resulted in me finding an issue (unlike the prior times) on the bench but I was correct in my diagnosis.

I wasn't saying it's your issue however I also didn't read you'd replaced the HPFP entirely.

But, not to sound rude, my post wasn't intending to start helping you directly, more to give you some more information to try solve your problem. Only parting comment I can really add is that if you've replaced so many parts maybe triple check they are all the same spec.

Hope you get it sorted, when you do it's probably going to be a pants-on-head moment where its something obvious once you find it.

 

[Dr Sheldon]

but I was 99.9% sure within the first 30 minutes it was the HPFP

however 99.99 % sure is NOT SURE - the same as I do not have a Clue

I'm 100% sure that is how I read and absorbed that !!

Only parting comment I can really add is that if you've replaced so many parts maybe triple check they are all the same spec.

Or put the old parts back on and restart the process correctly !! ??

If he could triple check parts he would be further down the line ??

 

[passdattdi]

Yes, of course. Helpful as guide and confirmed that when shopping for parts pay attention to detail . Other folks here, as you can see, have helped as well (in their own way) . I'm new to all this vw diesel stuff so learnings much as possible. I have not been able to provide test, scan results, but not because I don't want to and is why a reason for the frustration. At any rate, all appreciateed.

 

[jremi17]

Start a new thread with a autoscan please.

Hi!

No need to start a new thread.

I have the exact same 5211 - P0087 - Low fuel rail pressure code

However, mine showed up first time under heavy acceleration after filling a bad batch of Diesel.

Ended up for now with cleaning the tank twice, 3 fuel filters changed, HPFP replaced (second hand) and fuel rail replaced (second hand). All replacements are identical part number to what the car was fitted with.

Error still present under full load acceleration where the specified pressure is 1800 bar and actual around 1500-1600 bar. Just to mention, there is no other error code at all.

The car has been performance mapped (CFFB engine - 180ps vs stock 140ps) by previous owner, running with no DPF/EGR.

I guess I will have to avoid heavy accelerations, no time to research into this anymore.

If anyone finds the root cause of this, I would highly appreciate if you feedback.

 

[PetrolDave]

Error still present under full load acceleration where the specified pressure is 1800 bar and actual around 1500-1600 bar. Just to mention, there is no other error code at all.

The car has been performance mapped (CFFB engine - 180ps vs stock 140ps) by previous owner, running with no DPF/EGR.

Remap demands more flow/pressure than the fuel delivery system can provide - have you considered that the LPFP can't suppy enough flow for the HPFP to generate the extra pressure?

 

[jremi17]

Remap demands more flow/pressure than the fuel delivery system can provide - have you considered that the LPFP can't suppy enough flow for the HPFP to generate the extra pressure?

Hello,

Apologies, I forgot to mention I changed the low pressure fuel pump as well. So other than the lines and the injectors all fuel system has been replaced. Thank you!

 

[SaVAGeSoot]

where the specified pressure is 1800 bar and actual around 1500-1600 bar.

Oddly enough, those numbers jump out at me..... the older HPFPs maxxed out (operated) around the 1600 bar mark.... CP4x then bumped things up to 1800, 2000, etc...
I'd make sure the regulator is commanding the correct pressure, especially if you're using a used part.

 

[SaVAGeSoot]

Le this

 

[passdattdi]

Hi!

No need to start a new thread.

I have the exact same 5211 - P0087 - Low fuel rail pressure code

However, mine showed up first time under heavy acceleration after filling a bad batch of Diesel.

Ended up for now with cleaning the tank twice, 3 fuel filters changed, HPFP replaced (second hand) and fuel rail replaced (second hand). All replacements are identical part number to what the car was fitted with.

Error still present under full load acceleration where the specified pressure is 1800 bar and actual around 1500-1600 bar. Just to mention, there is no other error code at all.

The car has been performance mapped (CFFB engine - 180ps vs stock 140ps) by previous owner, running with no DPF/EGR.

I guess I will have to avoid heavy accelerations, no time to research into this anymore.

If anyone finds the root cause of this, I would highly appreciate if you feedback.

Similarly, when mine P0087 showed for first time, it was just after filling up at a liuqor store gas station, and unfortunately I did this more frequently than i should. But that morning i filled up, was heading up a hill and is when light came on. Since then, same as you, heavy acceleration and derate mode. My trouble shooting continues on another post starting over. Thanks for sharing.

 

[Uwe]

a liuqor store gas station

Alcohol has terrible lubricity.

-Uwe-