Lorryman100 wrote:

Check the relay under the drivers seat for corrosion and that all the pins are making contact. Check the loom around the relay holder for any signs of damage, water ingress or corrosion. Next thing would be a Ohms test on a glow plug with a DMM to check for an open circuit on any of the glow plugs and also check the glow plug rail for amps when the ignition is switched on and the glow plug cycle starts.


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From the symptoms you describe and that you can hear a relay click then it starts as normal then this is the first place I would look. It sounds as though the glow plugs are not receiving any power during the pre heat stage which causes the engine to start and then die

From another post to save me rewriting it:

Lorryman100 wrote:

During the preheat stage, the ECM receives the engine temperature from the cylinder head temperature (CHT) sensor and this is what determines the preheat time. The lower the temperature, the longer the preheat time. There is a maximum preheat time of about 8 seconds at -20°C or lower.
Once the engine has started, the glow plugs enter an after-glow phase. The after-glow phase only operates at engine speeds below 2500 rpm, above that the after-glow phase is stopped to increase the longevity of the glow plugs. There is a maximum after-glow time of about 30 seconds at -20°C or lower. If the CHT is above 50 degrees C there is no after glow.

If the connection is loose then yes that can be a cause of the glow plugs not working. A easy test is to use a DMM and do a voltage / amps check on the rail. The glow plugs draw a decent amperage so a loose connection will stop the maximum current from being delivered to the plug rail.

HTH

With the wet weather we have been receiving with the high humidity then the white smoke is normal on start up due to the low temp and high moisture levels in the air. As the ECM relies on the CHT sensor for the block temp to adjust the fuelling when starting disconnecting the CHT just exasperates the issues you are receiving as the ECM defaults to stored values. JMTW :thumbsup:

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Lorryman100 wrote:

As I am sure we all know a Diesel engine is generally not capable of pinking because prior to injection of the fuel it is only air that is being compressed, as there is no fuel mixed in, there is nothing to pre ignite (A petrol engine can pink due to pre ignition of the air/fuel mixture as a hot spot ignites the fuel prior to BTDC, eg: a faulty or wrong type of spark plug fitted). On the Puma fuel is delivered into the cylinder progressively in three stages and the knock you hear is due to the heavy compression of the air in the cylinder BTDC as the fuel ignites. But injection is not instantaneous, injection lag—the time required to build injection pressure and get it to the nozzle and “pop” it open, delays things. Once fuel is injected, ignition lag also occurs. Injector design and spray pattern, compression temperature, fuel cetane rating, and more influence ignition lag.
The “lag” during the compression stroke tends to cause diesel fuel to ignite spontaneously, thus creating the familiar diesel knock or “clatter” sound; upon ignition, cylinder pressure suddenly rises and “rings” the cylinder. This sound is noticeably louder on a cold engine as the EMS fuelling protocol allows for more fuel into the burn firstly to help overcome the cold mass of the engine block and get the engine started and then to keep it running as it warms up. The EMS knows the temperature of the engine via the CHT sensor, the air temp coming into the engine first at the MAF sensor and then before it goes into the cylinder from the MAP/T sensor. As the engine warms less fuel is used and the clatter subsides.
When the engine is warm and running at say 2000 rpm the amount of fuel required to maintain these revs depends on engine load and temp. Then if you depress the accelerator pedal, a higher load is put on the engine and more fuel is needed to accommodate this load which results in injector lag and cylinder pressure suddenly rising and rings the cylinder which sounds like Knock.
You can reduce the Knock by using a higher cetane fuel (I use BP Ultimate every tank) and you can raise the cetane number higher again by adding an additive to the fuel, I use Millers Oils Diesel Power Ecomax Fuel Additive Treatment every tank resulting in a quieter engine but you will never get rid of the clatter, knock or perceived pinking as that is the result of the combustion process in a diesel engine. HTH