Thread: TD5 fuel filter

Sorry mate doesn't work like that

ummm yeah they do

If they did not have a seat inside the injector that sealed off the nozzle between cycles so the constant flow fuel system employed to cool the injector's the fuel would just pour out the injector into the cylinder (think the same as a old hilbourne constant flow mechancial fuel injection system)
So when those seats wear or get damaged from particles in the fuel or even the fuel its self (remember that the tolerance's inside unit injectors are around 4 to 5 micron which is why most fuel filters have a filter medium of 2 micron and why the mesh screen is really useless other then catching rocks) so it does not need to be very large particles or moisture goes through the system and causes rust that pits the seat even when closed those seats will leak.
When they leak they only have one place to go and that's the cylinder while the engine is shut down and there is residual fuel system pressure which is held by the fuel regulator block which only holds pressure if there is no leak , and yes the leak can be a cracked head, injector seals or it will be the injector seat.

If its a cracked head or injector seals it will fill the sump full of diesel in around 1 day or roughly 3 hours of driving and an overnight stay, i know this from when i first got the vehicle the head had just been reconditioned i drove it for 2 hours parked it then drove it for anther hour at which point the engine tried to run away by running on its oil/fuel that had filled up the sump, when the head was removed and check they found an injector tube was cracked and needed welding up.

If a injector seat goes bad it will fill the pot with fuel that it is leaking on but only when that cylinder is not on a compression stroke where it has more then 100psi cylinder pressure as the cylinder pressure will over come the residual fuel line pressure and stop it from leaking,
(btw that is one way to check which injector is leaking is you remove the exhaust manifold and go through each injector giving a set amount of time before firing the engine up and seeing which cylinder is the one blowing the white smoke from),
But this wont apply if your engine is worn and the cylinders are not holding pressure and bleeding it off over a few hours so long as there is still fuel line pressure that is enough to overcome the cylinder pressure it will also leak.

if you think none of that can happen due to the electric solenoid all that does is allow the fuel seat to become unseated when the camshaft has the plunger depressed which if your even more unlucky will mean that you get a full squirt from the plunger as well as the residual fuel line pressure.

one of the most common test's for unit injectors in workshops is to get an old head cut it up so you have 1 cylinder you then put fuel lines on both sides of the fuel rail in the head prime it then bring it up to residual fuel line pressure then get a bit of paper and put it under the injector if it makes the paper wet with fuel from the tip and you confirm this by cleaning the tip with brake clean then re testing itand its wet again bingo you have a dripping injector that is now rooted and you need a new one

Originally Posted by Roverlord off road spares

You have a very valid point, a system that has mainly been trouble free on a vehicle up to 17 years old now . Yes the odd fuel pump failure or fuel block, but mainly trouble free.

x4 why re invent the wheel? Plus the fact I couldn't be arsed to do this.
Rock sliders and steering guard? yes.