407 HDi 2.7 high diesel fuel pressure P0088 and P0087

[407]

Hi

Car was running great on highway and then went into limp mode / cruise control error and MIL light

Diag is showing P0088 fuel pressure is higher that reference value 361 bar / 36100 kpa psi v 282 bar / 28200 kpa reference value at 1216 rpm and P0087 regulation of fuel pressure is lower that reference value 760 bar / 76000 kpa v 941 bar / 94100 kpa reference value at 2144 rpm.

Looking at a pic of a 1920HJ injector pump, there are two "sensors/ regulators"

No1 I assume is the pressure regulator (Peugeot 1933.41 / OEM part A2C59506225)

what is the other one and what does it do ?

I assume one or the other sensor / regulator is faulty assuming the pump is okay

Given the above, any other ideas - car seems to run okay otherwise

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Alternatively it could be the diesel high pressure sensor 1570H4 which seems cheaper and easier to replace

Any ideas ?

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Seems No 2 in my first pic looks like a high pressure pump (low pressure side) / fuel volume regulator 5655C0025 / SKCVQ-4550024 (Autodoc and other sites quote 1920EP but that seem like it the whole injection pump)

Courtesy viewtopic.php?t=65339

Also high pressure reference values

at idle 298 bar = 29,800 Kpa

full throttle 1350 bar = 135,000 Kpa

so my readings seem to be in spec

Car runs well (in limp mode max 2900 rpm) except for the OBD code P0088 and a MIL light

Plan is to change the diesel filter (some post mention this as the issue and mine is only 5000 / 6 months old)

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So changed the diesel filter and it looked bit dirty (only changed 6 months ago). No shavings at the bottom of the filter housing

Some prior posts say changing the filter might fix the P0088 issue but other says this is the low pressure side so unlikely to affect it.

Went for a drive (30 kms) to test and on the way back a wake the dead hammering / knocking noise started near the diesel pump along with new diesel leaks (eg over pressure causing leaks it seems - leaks never happened before so a bit stumped why it started leaking now unless pressure is exceeding normal levels) .

Managed to get home and suspect that the fuel volume regulator 5655C0025 / SKCVQ-4550024 (No 20 in the diag) is no longer regulating, causing the pump to build up pressure. The hammering noise could be due to cavitation or over pressure within the pump.

Looks like the pump needs to come off to test.

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Seems No 20 is a Siemens VDO Diesel Volume Control Valve VCV A2C20000719Z (not available from PSA as a part)

Rather expensive it appears @ £190 and seems only genuine part (no after market available)

Also a VDO Lion V6 Base Repair parts diagram with part numbers and measurements

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So checked the diesel pump and both solenoids (no 19 and 20) seem to work okay (eg pulled No 20 out and tested on 12 volts and move in and out , multlimeter shows connectivity with No 19 under the pump connected by a wiring loom which would need to pump removed to get to it).

Replaced the pressure sensor with a new one just in case.

Restarted and still have the knocking sounds.

It seems like its two options

a) the diesel pump high pressure

b) leaking injectors causing misfire, albeit the engine does not seems to shake

I've attached video. The "smoke" is diesel mist" so related to high pressure

https://1drv.ms/v/c/14006f5528e678c7/ES ... A?e=sVLSQe

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So I've bitten the bullet and have started taking the diesel pump out to check the VCV (at the bottom of the pump so no way to access) but hit a road block.

Seems the last bolt (top right hand when lying on top of the engine) is semi-covered by the two oil separator female pipes and they are metal and they can't be moved (I've tried) .

Any ideas on how this last bolt is removed ? - see pic #1

I've looked at taking the diesel fuel filter off but there are a few bolts that are "impossible" to get to so I have left it in place for now and still may not solve the clearance issue.

The good news

a) the plastic belt cover slips over the gear of the diesel oil pump - I had assumed I would need to remove the gears to get the pump off - see pic #2

b) I mangled most of the clip joints on the quick connects (they are so brittle) - I've ordered some 9.49 mm Urea Tube Pipe Joint Clips ones off Aliexpress and they fit (just need to push them in the right way around ) - see pics #3 and #4 I would hate to think what a new genuine diesel pipe set would cost

One other question - Where does the injector leak off pipe go to after the diesel temp sensor (removed in the pic) ? eg back to the fuel tank or back to the diesel filter ? - I've blown air thru it and diesel comes back it thru the pipes near the diesel filter - eg just in case a blocked leak off pipe is the problem causing the high pressure given all the issues started with the temp sensor leaking diesel fuel - pic #5