bensla
Member Since: 02 May 2023
Location: Trowbridge
Posts: 141
  
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| Diesel leak and 'fuel rail pressure low' error |
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I have a slow diesel leak - just a bit wet underneath by the diesel cooler - but it looks like it's coming from further up. Yesterday shortly after a full throttle acceleration I had the full limp mode experience with warnings about everything showing on the screen. I connected my scan tool and the main error seemed to be the 'fuel rial pressure low'. I cleared the code and drove home fine avoiding full throttle.
From reading on here it seems the common cause of diesel leaks is leak off valve seals - so if that is the cause of my leak can that also cause low fuel rail pressure error? Or would the leak off valves be on the wrong side of the fuel rail to cause that error?
Thanks
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 24th Jul 2023 8:18 am |
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Dashdash
Member Since: 15 Jan 2023
Location: Barcelona
Posts: 29
 
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Hi Bensia.
I share the same problem with my 2008 D3
Did you solve this issue, and if so can you please share the solution?
Thank you
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| 4th Jan 2024 5:59 am |
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bensla
Member Since: 02 May 2023
Location: Trowbridge
Posts: 141
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The diesel leak was unrelated. The P0087 was the, apparently quite common, problem associated with aftermarket high pressure fuel pumps. When I got my car it had a Lucas pump from Euro Car Parts on it after the previous owner having replacing the original one about a year before. Technically it was still under warranty but after seeing so many issues reported with them I didn’t want to go down that road.
I assumed it was a genuine replacement so overlooked this at the time. After lots of misdiagnosis (I thought I had an issue with low pressure pump due to trying to measure flow from the schrader valve without taking out the valve core) I got a second hand high pressure fuel pump from Jack at https://landroverpartsuk.com/- fitted it myself based on the guide on here - 1600 miles later, problem solved. It’s a pretty complex job - took me about two days (comfortable timing with lots of trips to get tools etc).
The diagnosis route is something like:
- Check for low pressure side issues with pressure and flow. There is a guide on here. Just make sure to take the core out of the schrader valve when taking measurements. If there’s a restriction there it might be a blockage or the low pressure in-tank pump.
- Check everywhere for diesel leaks around the injectors, fuel rail etc.
- If that’s all ok then it’s on the high pressure side. The sensor reporting the P0087 is on the end of the fuel rail and you can read its live values on an app like Car Scanner with a Bluetooth OBDII reader. (When reading fuel rail pressure, enable the pressure control valve and volume control valve values as well. These are the two values sent to the high pressure pump to adjust its output. Here’s a great video showing how they work: ) I used the LELink one from Amazon. If you look at the live readings you can confirm if you think the issue is with the sensor (not common apparently) or if the pressure is actually too low for an expected scenario. What seems to be the issue with the aftermarket pumps is the valves on the pump are slow to respond when making small adjustments. I.e you increase throttle a tiny amount, then you get the error due to the valve not moving. Of course this might be the failure mode for an old original unit too. What this looks like on the live data is the Pressure control valve going up but no corresponding increase in fuel rail pressure. The valve readouts show requested values not actual so what’s happening is the valve isn’t actually allowing more pressure.
Feel free to ask any questions - happy to have this up here for others too.
Last edited by bensla on 4th Jan 2024 8:39 am. Edited 1 time in total
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| 4th Jan 2024 7:22 am |
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bensla
Member Since: 02 May 2023
Location: Trowbridge
Posts: 141
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I should add - this first instance of the P0087 I think might well have been the diesel leak I mentioned. After I fixed that it was ok until I started getting the same error but on light acceleration which was the HPFP.
Last edited by bensla on 4th Jan 2024 8:39 am. Edited 1 time in total
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| 4th Jan 2024 8:25 am |
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