No power to the glow plugs auy engine sharan 2005

[Marios]

Hi there,

i am new to this forum
looks like i have an issue, No power to the glow plugs. when i first start the car in the morning it will start after about 8 secs turning the engine
found out that no power to the glow plugs, for the rest of the day is fine
relay gets power to the 3 pins with key in position2  but not giving it to the glow plugs
85, 86, and 30 they have current 87 goes to the glow plugs no(relay doesn't click, of curse as there is no ground )
checked manually the relay and works ok
no errors via vcds
if i give electricity tho the glow plugs directly from the battery for 3 secs   car starts within 1-2 secs
also the light in the dashboard for the glow plugs when turn key to position 2 illuminates  for 1-2 secs
question is
were is the 40 or 50 amps fuse? the car is sharan 2005 auy engine 1.9 pd tdi
what other components are playing role to activate the relay as i get electricity on 85,86 and 30 pins and if i cut the 85 pin and short, relay side, to earth then relay clicks and electricity sent to the glow plugs
so i think 85 pin should something ground it and is not
were  is the temp.sensor which is responsible for the glow plugs, outside temp sensor ok(i see the readings in the ac panel , on the radiator(3 pins) ok
if anyone can provide a diagram of the glow plugs-ecu- wiring etc with full detail description.............would highly appropriate it
any advice pls
millions of thanks

[christiant]

On the PD TDI engine, the glow plugs would only come on for pre-start glow if the temperature is below 7C. A direct injection engine hardly needs any preheating to start. I think you problem is elsewhere most likely fuel related eg air in fuel lines, tandem pump or injector seals or worn cam.

[Marios]

milions of thanks for you reply
clear but how u explain that if i give electricity direct to the glow plugs the car  start straight away without any issues even if it sits for 3 days not just one?
and is it possible to check the fuel system via vcds?
pls advice how were and what values i need to see
cam ok that u can inspect visually

[johnnyroper]

My old PD used to briefly flash the glow light even on warm days however the plugs still heated on cold start despite not needing them. It is the coolant temp sensor feedback to ECU that determines the glow time.

Have a check on measure blocks see what your coolant temp is reading,rule of thumb on a cold engine it should be roughly same as fuel temp sensor.

If I remember correctly the ECU does indeed switch and earth to energise glow plug relay?

Coolant temp sensor is located at the rear of the water housing that is below the tandem pump.

It is also worth keying ignition on and off a few times to see if it starts better then as it could be some fuel run back also.

[christiant]

Try to get the plug off of the temp sensor, which is under the tandem pump. There is a plastic flange attached to the side of the head. That will make the plugs go on regardless of the coolant temp reading. As mentioned above you can check the coolant sensor reading and compare it to the fuel temp sensor reading to rule that out. You can also adjust the glow time using vcds. I have done that to mine. It also makes the plugs come on at higher temps if memory serves correctly. The wiring harness for the plugs also could be damaged, the wires inside crack from the heat so that's worth checking too. Are you checking relay 103? Does it smoke and miss when you start it cold? It's worth taking the valve cover off and looking for camshaft wear as that caused mine to start hard when cold even in warm weather.. I would also check the torsion value for the camshaft.  The fuel system could be sucking in air and fuel could be running back to the tank.