D5 engine starting on 4 cylinders
 

Does anyone know if a Euro 3 D5 engine will start easily on 4 cylinders rather than 5 ? I am planning to use a common rail outlet nut with a copper blanking plate to seal off the outlet to the suspect injector which I think may be causing the rail to lose pressure and prevent the engine starting. A cranking leak off test has not shown conclusively if its an injector and this seems easier than swopping the injector.

Bernard, just do the one minute proper test with tubes and bottles.
It'll be more conclusive.
As for your blanking idea.....I can't help thinking 1000's of psi of fuel with nowhere to go is a bad idea.

I still don't think it's an injector though.....
Good luck, whatever you try.

Dont worry , I have a strong sense of self preservation and will be sat behind the steering wheel with the bonnet down, if the engine starts then I will switch off again immediately and make sure there is no one else within range , will be interesting to see if the copper blank is deformed by the pressure as its only 2mm thick. There is definitely not enough pressure in the common rail at the moment but will also try one more leak off test with the bottles before blanking off the rail.

Indeed ,but the engine needs to be running first

Normally its a bad idea , but you can seal it of with the injector itself and just remove the electrical solenoid connector from that injector

You can see with the torque app when cranking the engine that the fuelpressure is insufficient or not (it needs to be 350 bar)
Have you ruled out your intankpump bernard?
You had problems with it in the past? That also affects fuelpressure in the rail

Personally i would extract all 5 injectors and take them to a testbench at a boschservice (doesnt cost much) and replace the injecors who are tested (near)faulty with second hand injectors (wich are testbenched first before assembly) dont refurbise them

Common work shop trick is to place a suitable sized ball bearing in the injector fitting to seal it of from the rail during cranking rail pressure tests in order to locate the failing injector

I tried disconnecting the injectors one by one but suspect that if it is one of them its leaking back even with no electrical input, is this possible ? The common rail is not even holding residual pressure when compared to a good D5. I did have problems with my V70 D5 in tank pump so have a good idea about testing these which I have done on the S60 D5 which is the non starter, I am certain its not the in tank pump or contaminated fuel. I have a working spare injector but problem is the one I tried to remove already is stuck tight so I want to try other tests first. I already made a mistake in assuming the high pressure pump was faulty, that assumption was made because with ignition on there was a buzzing noise coming from the regulator mounted on the high pressure pump , removing the electrical connector it went away and came back when plugged back in. The V70 D5 does not make the same noise, its as though the ecu on the S60 was sending a permanent signal to open the regulator which might point to a faulty ecu or maybe the fuel rail sensor is faulty. The injection pumps were swopped over and the buzzing sound stopped. A faulty ecu would be the least desirable fault as could cost £250 for a refurb but no indication at the moment thats the cause. I suspect that the initial build up of pressure in the common rail is a 100% mechanical process and does not need input from the ecu until it starts opening the injectors and then later it opens the injection pump mounted regulator, the initial pressure necessary to start is not being built up ?

Thats great thanks, thats just what I had in mind and I should have thought of using a ball bearing instead of a copper blank.

Bernard,

The is a misconception that common rail injectors are purely electrically operated both the solenoid type and peizo not the case. They are electro mechanical, when the injector is closed on both types high pressure diesel is present both below the needle pint and above the needle in the bleed chamber.

This equal pressure keeps the needle closed on its seat. When an injector is triggered the solenoid type and piezo both lift a ball valve off a sealing seat in the upper bleed chamber, This creates a pressure drop at the top bleed chamber which allows the high pressure diesel in the lower chamber to mechanically lift the needle off its seat and to inject fuel. Injectors loose pressure by generating a sealing fault in the upper chamber. In normal use when the injector functions the fuel that bleeds from the upper chamber is what you see at the leak off pipes. When a sealing fault is present then high pressure diesel leaks past the upper chamber when in the closed position leading to loss of pressure in the rail.

On of the challengers of diagnosing a low pressure fault on the high pressure side is where is it. Often over looked early in the diagnostics is good cranking RPM, engine must achieve 220-250 rpm (scan tool live data) cranking speed for the ECU to allow injection. A failed CKP will be no pressure and no start. Poor in-tank pump pressure and blocked filter along with air ingress will lead to low pressure on the high pressure side. A poor performing Inlet Metering Valve (IMV) AKA Volume control valve will also lead to low pressure faults.

Also if the ECU sees a too high a pressure at the rail it will shut down injection. As a quick test locate the rail pressure sensor and its signal wire, back probe an connect to battery ground at Key on engine off the rail sensor will generate a circuit plausibility test voltage of 0.5v. During cranking with a pressure of 300-500 BAR voltage should reach 1v and at idle 1.3v.

If voltage is lower than 1v the are 2 ways to go from here to establish where the pressure loss may be, either for the injector leak off test to locate bad injector. If injectors are good then the ball bearings placed in the injector pipe fittings to seal the rail will allow you to conduct a maximum cranking pressure test two DVM are useful one on the rail pressure sensor and a second set to duty cycle on the IMV. During cranking the rail voltage should rise quickly to around 4-4.7v and to lower the pressure the IMV should duty cycle to 90% (closed = no fuel entering pump). Poor rail pressure could now be at the mechanical relief valve on the rail, remove pipe check for excess leakage under cranking.

Hope this may be of help.

Thats great info , gives me plenty to go at, also think its probably about time I traded the Nokia 6210 in for an android phone so I can run the torque app.