Td5 D2 engine - FPR Fuel Pressure Regulator

The recent episode with the leaking Diesel had me immediately suspecting that the (FPR) Fuel Pressure Regulator mounted on the lower rear cylinder head had failed again..

It was replaced 4 years ago and with it being a 'Britpart' item, I have always expected it to give up the ghost!  Britpart seem to have a bit of a reputation within the LR community for unreliable parts. Regretfully, I can only add to that from personal experience and I always wince when I buy something blind online and it arrives in the dreaded 'blue-box'!!

With that in mind and to give me some early warning of imminent future failure, I fitted it with a length of blue vacuum-tube (sourced from the EGR removal) connected to the 'leak-off' tube and routed down below the chassis to drain onto the ground behind the front wheel. 

Removing the unit from the vehicle is quite an undertaking in itself and it is well covered in the online blogs. Here is the useful instruction sheet provided with the replacement unit.

Thumbs up to Britpart here, they even include a very handy 'elastic-band' tip for holding and positioning the bolts and gasket during the re-assembly. It's the kind of tip that can be utilised on any other awkward or restricted install.

To that end, I would offer the use of a small inspection mirror to get eyes on the situation and particularly on the location of the lower bolt. (Which is right next to a manifold nut and easily confused 'blind'). Furthermore, if the front wheel is removed, better access to the lower bolt can be had by looking through the gap between the inner arch and the chassis rail from within the wheel arch. Direct line of sight to the bolt head is possible and the combined reach of two or three lengthy socket extension bars makes the job a lot easier.

Once it is all re-connected, the fuel system will need purging of air before trying to start the engine.. It is a fairly straightforward operation and loaded with satisfaction...

DO NOT THROW THE OLD UNIT AWAY!!

Having the old original unit lying around 'spare' gave me the opportunity to refurbish it with new o-rings and a new regulator rather then forking out again for a complete unit. I like the idea of having a spare unit handy just in case the mounted one fails.... 

Here is the removed Fuel Pressure Regulator complete with its thin metal plate gasket. There are two versions of the FPR based on whether the Td5 engine is an early 'two-pipe' or later 15P 'three-pipe' model. Hx is a three-pipe 15P engine. There are also slight pattern design differences between the gaskets.

The 'fit' of the gasket seen above looks a bit odd against the machined face of the FPR body. Despite it being metal, it is definitely not re-usable as it's design allows segments of its surface to be crushed flat to achieve the effective seal. 

The gasket is readily available separately but it's better to buy it as part of the re-furb kit many independents offer on E-bay. That way you also get the required pipe-sealing o-rings and maybe even a new regulator unit as well.

The crushable sealing lines can clearly be seen on the triangular metal gasket plates above. This photo also shows the slight difference in the pattern. The 15P Td5 gasket is on the left.

The above re-furb kit even includes two o-rings to fit the actual pressure regulator. They are not available from LR and this E-bay seller has sourced them independently. I bought this kit myself and everything else arrived in LR OEM  plastic bags. There was also a comprehensive instruction sheet, well recommended. 

REFURBING THE REGULATOR

The exploded view above is from 'Rave'. All of the pipes (5,4,14) have the same O-ring seals but the fuel temp sensor (6) has its own 'bonded' seal. Don't forget to renew the O-ring (12) that sits on the cylinder head itself. The expensive 'gauze filter' (13) sits inside the cylinder head and should be inspected. It is extremely fine fragile tubular wire mesh and should be clean and clear. All are available from LR dealers or online. 

The regulator (10) and it's 'O'ring seals (8,11) are not available separately from LR and further searching for suitable replacements is necessary. 

   .. a worn, crushed O-ring seal..

   .. a new un-crushed seal..

Two of the pipe unions on the FPR body (4,6).  If removed, new o-rings must be used..

This is the fuel temp sensor (6). If removed it has its own special 'bonded' sealing washer that is readily available..

The regulator is held in place by a sturdy circlip which is easily removed with the right tool! 

Unfortunately, that was not to hand so I had to fabricate one.....

Using a spare pair of needle nosed pliers and some craft files..

   ..It fits!!...

In this photo the circlip has been removed and the regulator is free to remove. It is a tight interference fit and really should not come out easily! Use of a pair of water pliers or mole-grips will help. If you look closely the surface is scratched from the jaws gripping around it. 

To remove the regulator I had to use lots of WD40, mole-grips and a wooden punch to sharply tap on the flange surrounding the regulator body. I was careful to tap 'around the compass' as it where to ensure the regulator body came out evenly. 

Re-mounting it is a simple push-fit with a reassuring 'click'.

This little component is the Fuel Pressure Regulator itself and it's performance is crucial to the running of the engine. It is fitted with 2 'O'- rings that can be seen to be compressed and must be renewed if the unit is to be re-used. 

This particular one developed a fault internally that allowed diesel to leak out from the little hole on its base and wash down the engine block all over the starter motor and eventually drip on the ground in a grungy oily mess that was initially difficult to diagnose. 

The replacement unit has a short pipe soldered over the hole to act as a 'leak-off' pipe. I attached a length of suitable tubing to it so any future leaks are immediately apparent. 

I am so tempted to open up this case just to see what's inside.....

Research has told me there is a small flexible diaphragm inside it that responds to the fuel pressure and moves to 'open' internal passages if that set pressure is exceeded. Over time the diaphragm wears/leaks and causes the problem.. It will still function with a small leak, but if left untreated it will eventually fail and full pressure diesel will spurt out of the hole and not into the engine....messy to say the least!!

Stamped on the base is two sets of numbers. The first '30.04.02' is I believe the manufacture date. This would tie in with the age of Hx (first registered 11.09.02). It kind of points to being the original component and gave over 11 years service... That leads me to think these things have a 'shelf-life' probably related to the rubber diaphragm going off or 'curing' in some way.

The other number on the end is ' MSA100000 '

This is the Land Rover part number but it was never available from them (or indeed the big aftermarket suppliers) as a seperate item. LR would only sell the complete unit.

A quick search online soon brings up cross - referenced numbers for the same component used by other vehicle manufacturers.

Practically every vehicle with a fuel injected engine has one of these components fitted somewhere in its fuel system. They are available in differing pressure ratings (and designs) but the cross referencing of numbers soon gets me settled on a Bosch component that is common to many VAG vehicles. 

BOSCH 0280160575 

There are many aftermarket suppliers of these units and the prices can range widely from under a tenner to over £60. The Bosch branded regulator comes in at around £40 and is the one to get.

This image from the Web shows the Bosch component fitted with its 'leak-off' tube, but I believe that some VAG applications actually pull a vacuum from here? I have not purchased one of these yet to re-furb the spare FPR due to the issue with the shelf-life date. 

Studying images of Bosch branded regulators online shows some to be made in China! Which kind of negates that whole 'German build quality' thing!!

Swapping these components around is a trick that the modders use to boost a lower pressure system up to a higher pressure one. The pay off of a higher fuel pressure is more fuel in the engine and more power released. 

The Td5 engine operates at 4 Bar which is the designed limit for this regulator so things are kept stock as it were. ..  But I do wonder if there are advantages to be had with a higher pressure regulator, 'bigger' injectors and/or an engine re-map?

WHAT'S WITH ALL THE PRESSURE ?

Diagram above shows the Td5 fuel system. The FPR is item 13 and it's size underplays its importance. The Td5 was never fitted with any on board fuel pressure reading gauge and it's been left to industrious people to plumb in their own mainly for the diagnostic benefit.

This has shown that the fuel pump can produce 4 - 6 bar in the High Pressure supply line (8). This variation probably takes into account manufacturing and ageing tolerances. 

It falls to the FPR to maintain the designed 4 bar pressure around the cylinder head that feeds the injectors. Once the fuel is in the injector body, the internal workings of the injector can increase the pressure at the injector tip to a staggering 1750 bar for the moment of injection. 

It's no wonder all that compression results in the need to cool the fuel before sending it back to the tank via the filter. 

That figure of 1750 bar is for a 15P / EU3 Td5.

The earlier Td5 has an injection pressure of 1500 bar. They both use a 4bar regulator so I guess the only way to increase the injection pressure is to modify the injectors....