P008700 - Fuel Rail/System Pressure - Too Low

[sgt1297]

2012 1.2tdi Greenline Fabia II. Keeps throwing up the fault code P008700. Coil/glow plug light flashes for the remainder of the journey but resets when you come to start the car again.

Does not go into limp mode and is intermittent.

Changed fuel filter, in tank lift pump, fuel rail, fuel rail pressure sensor and fuel rail pressure regulator, but still appears periodically.

Any suggestions as to the cause or other courses of action to try and eliminate this issue.

Thanks

 

[Bertie90]

looks like the only thing you didn't change in the fuel system is the high pressure fuel pump.

[sgt1297]

That is the case but that is an expensive and time consuming job I would rather not do. This has been rumbling on for 6 months now, so whatever it is it can’t be that serious🙏  Will live with it until it is no longer intermittent, then I will know what it is. 

 

[skoman]

I will say this with the greatest respect before you start throwing any more parts at it get it properly diagnosed. Have you thoroughly checked all the wiring ? If you need a wiring diagram I can supply one for you.

[sgt1297]

I have had it to a local VAG specialist who did not pinpoint anything specific but suggested the fuel rail sensors.

Any assistance would be very much appreciated.

Thank you

[skoman]

If you can DM your email address, I will send you over some wiring diagrams. Your engine code should be CFWA can you confirm?

Edited 18 August, 2020 by skoman

[globalste]

Have you got a tuning box fitted to it?

[sgt1297]

No. It’s had no mods at all. 

[globalste]

Oh, that was my first thought.  Has it had the ea189 emissions update?

[skoman]

Have you taken off the fuel metering valve (N290) on the fuel pump itself?  If not take that off and check the seals and also check for any metal shaving inside the pump. If you find any shaving inside that means the fuel pump has had it

[sgt1297]

No I haven't, but it is my next task when I manage to get it for a service in a few weeks as it is my sons. He's just done a 300 mile round trip and the fault came on once on the way there and not at all on the way back. Very frustrating. 

[sgt1297]

Update on what I have done so far:

Removed the N290 Metering Valve - clean as a whistle. No debris 

Replaced the in line pressure regulator/filter under the rear offside.

Checked all connections I can investigate.

When I drive the car I do not get the fault.

When my son drove the car after the last service he phoned me to say the light was back on!

He hadn't even gone a mile.

Driving style would appear to influence the occurrences. 

It would appear that the car doesn't like being accelerated from low revs.

It is an underpowered car designed for economy.

If you try and accelerate hard from 1500 rpm the light comes on and the low rail pressure fault is recorded.

My advice to him was to keep the revs a little higher and use the gearbox more when wanting to accelerate.

Fault light hardly ever comes on, and when it does it is when combines low revs and high gear to accelerate.

Living with it for now.

Anyone else experienced a similar phenomenon?

[sepulchrave]

The clue here is that the revs are low, this means the common rail fuel pump is not spinning fast enough to keep the rail pressure up,  the turbo is boosting and the ECU is telling the injectors to dump the fuel in but the rail pressure is dropping below ECU minimum spec. Possibly a software update from Skoda will stop it.

[sgt1297]

Thank you. I will explore that with Skoda.

[skoman]

1 hour ago, sepulchrave said:

The clue here is that the revs are low, this means the common rail fuel pump is not spinning fast enough to keep the rail pressure up,  the turbo is boosting and the ECU is telling the injectors to dump the fuel in but the rail pressure is dropping below ECU minimum spec. Possibly a software update from Skoda will stop it.

It may also be worth getting someone with VCDS and looking at the measuring blocks for the injectors and fuel system in general and try to pinpoint what is happening regarding fuel delivery under load.

 

It could be a leaky injector which could be dumping fuel causing low fuel pressure.   

[sgt1297]

Had to a local VAG specialist for some diagnostics and declared the injectors were all good and could not explain the issue.

 

[globalste]

Where are you based sgt1297?  I think you need a specialist electronics VAG garage to look at it.  Don’t go to Skoda asking for an ECU update because they will just give you the latest emissions software.

[Hargur]

I faces exact problem with my skoda yeti 2012, glow plug light lit up when you accelarate hard. 
Not reaolved yet

[thomasaspin]

I had this problem and it was the alternator not giving enough voltage to keep the fuel rail pressure high enough , was enough to run car though 

[sgt1297]

This is my son's car and when I drive it the problem doesn't come up. As soon as he would drive it, the fault would show up before he had travelled a few hundred yards. He was changing gear far too early and accelerating far too hard at low revs which would bring on the fault. Fault doesn't show up any more. thomasaspin, how did you diagnose the alternator was the problem? What voltage were you getting?

 

[thomasaspin]

19 hours ago, sgt1297 said:

This is my son's car and when I drive it the problem doesn't come up. As soon as he would drive it, the fault would show up before he had travelled a few hundred yards. He was changing gear far too early and accelerating far too hard at low revs which would bring on the fault. Fault doesn't show up any more. thomasaspin, how did you diagnose the alternator was the problem? What voltage were you getting?

 

I put everything on lights, ac , radio and was barely getting 13v when now I get around 14v on idle under load 

[Hargur]

Than how did you resolved the issue

[sgt1297]

Hargur, I haven’t found a solution, or at least I haven’t found a component that has been found to be faulty. Use of the gear box to keep the revs above 1500 rpm and not trying to accelerate too hard from low revs has meant the light doesn’t come on. Have you established what the fault code is that brings on the light?You

[Hargur]

Yes, The fault code is same P008700 - Fuel Rail/System Pressure - Too Low. But I have not checked the voltage yet.

[thomasaspin]

13 hours ago, Hargur said:

Than how did you resolved the issue

Changed the alternator