kingpleb wrote:

The leak off test is a red herring when the injectors aren't firing as they need to bleed all fuel sent to them away as its not being used when it gets above their set pressure

The injector leak off is tested with the ignition on, not running or cranking, so the above is incorrect

You can do a high pressure leak off test, but wouldn't help diagnose a non start issue.

I've never done a leak off test on a non running engine...


Bit pointless as without it running the pressure cant stay high enough for the injectors to return the fluid thru their own valve. FFRR MY06 facelift With TDV8 Alloys Zeros/ATR's
Mantec Sump Guard, Rigid Load liner, MY10 BT upgrade.

Looks like I have been doing it wrong for the last 10 years then

5 years in a (Land Rover) main dealer, 4 years at an LR specialist, and nearly 12 months being self employed fixing Land Rovers

I wonder if I should give it up and try another line of work.


FWIW, the purpose of a leak off test, is to determine the internal fuel leakage of the injectors. If there is a leak, there will be excessive leak off, and the injector looses pressure. Because of this loss of pressure, the spray pattern is too weak, and does not burn properly. More of an issue with the TD4 in the Freelander, a single injector dropping out is more of an issue than on the TD6, where a single injector will more than likely go unnoticed...

If the ignition is on but the engine is not running then how can there be any decent pressure at the injectors?!
All that key position does is fire off the intank balancing pump if needed, and the main low pressure pump which won't push anything past the high pressure pump. FFRR MY06 facelift With TDV8 Alloys Zeros/ATR's
Mantec Sump Guard, Rigid Load liner, MY10 BT upgrade.

There should be a constant flow of fuel through the HPFP to the fuel rail, from the low pressure feed. Unless there is a fault in the system...

The pumps design shouldn't be allowing any fuel to flow past the hpfp at all, it seals as it pumps so unless it's shafted it shouldn't be bleeding any fuel past it.

I have never heard of anyone trying to test leak off with the engine not running.. I'm happy to be proven wrong but in many years of playingnwith engines and diesels on varying fuels I've never come across it.. FFRR MY06 facelift With TDV8 Alloys Zeros/ATR's
Mantec Sump Guard, Rigid Load liner, MY10 BT upgrade.

This clearly shows my point on the M57 engine.



Notice that before he starts he gets NOTHING in the bottles.
Then when he starts you can see one injector is clearly stuffed and the others aren't too bad but will need retesting when one isn't bleeding the fuel pressure straight out of it.

The injector above is clearly shot and is one of the worst i've seen so possible not even able to be refurbished. FFRR MY06 facelift With TDV8 Alloys Zeros/ATR's
Mantec Sump Guard, Rigid Load liner, MY10 BT upgrade.

kingpleb wrote:

I have never heard of anyone trying to test leak off with the engine not running..

Quote:

The internal leakage the injector is caused by a worn sealing element between the low pressure and the high pressure side, which results in the return volume from the injector increasing to an unacceptable level.
Consequently, it is not possible to build up the rail pressure required to start the engine

I still can't seenhow the injector can have a supply with out the hpfp supplying pressure unless the hpfp is leaking fluid passed itself somehow. FFRR MY06 facelift With TDV8 Alloys Zeros/ATR's
Mantec Sump Guard, Rigid Load liner, MY10 BT upgrade.

If you aren't sure about the high pressure supply to the fuel rail being enough, a simple check for you, just to eliminate another possible cause.
Remove the diesel supply pipe to the high pressure pump. Inside there is a piston which can stick. With some stiff wire (16swg welding wire is ideal) press down on the piston inside the pipe, it should move with no effort. Mine was stuck solid (replacement engine was on a pallet for 7 years). what makes it harder to see is a coolant pipe directly over the top of it so you can't see down the pipe.
Might not be an issue with yours, but worth a check for the 5 minutes it takes.

Steve. 1968 Series IIA Pastel Green, nearly there project

Hey Vaz.

Are you implying that if it's moves the pump is ok? If it stiff the pump is not?

Might give it quick shot, I really can't think of anything else apart from the pump at this stage which could be causing the issue.

No, what I meant to say is, that it can stick in place, usually if the pump or engine has been standing for a long while. It would seem to me as though it is a one way valve. Most likely to stop diesel syphoning back to the tank when engine is stopped.
On the new engine I fitted, the engine had been stood on a pallet since Feb 2007, so had stuck in the closed position. Hence when I cranked the engine, there was low pressure from the fuel filter to the high pressure pump, but next to nothing in the injector fuel rail.
I can't remember the exact figures for the pressure in the injector rail but when cranking I would have thought that you need at least 300 bar (4,300 psi).
I can check tomorrow and let you know the figures for low pressure to pump and high pressure to injector rail.

Steve. 1968 Series IIA Pastel Green, nearly there project

Just checked fuel pressures.
Pre supply pressure from fuel filter 0.9 bar (13 psi).
Pressure from high pressure fuel pump to injector rail 317.3 bar (4,602 psi).

HTH,
Steve. 1968 Series IIA Pastel Green, nearly there project

Hi there I was wondering how you got on.
I have exactly the same faults.

I have checked all wiring all sensors fuel pressure is bang on the money.
Injectors are not faulty
Ecu tested

I know think it maybe a can error from the body control to the instrument pack

This In turn not allowing the ecu to send power to open the injectors.

Can anyone help with info.

It's my own car and I am a garage owner I have several diagnostic machines and now bought Range Rover technology

Awaiting a vcm from China to communicate better with the car


Regards

Stuart