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Discussion Starter #1
Hello All,
If any of you have had experience with the diesel engine quick start function I would appreciate your advice. I have been working on this for a few weeks with limited success but not repeatable after the first start of the day. I have replaced the fuel module in the tank (the lift pump and check valve were not working, fuel filter now has a level in it), replaced the camshaft sensor G40 (original sensor was pulsing on from 0 to + 540mV new sensor is 5V negative going pulses), check all of the glow plugs with a Fluke meter and outside of the engine ( ambient temp too high for initial heating, all plugs heat up in the extended glow period of 4 minutes), replaced the check valve located on top of the filter, captured the camshaft/crankshaft sensors with my oscilloscope ( looks just like the signal pattern in the manual), replaced 680 amp VW battery with same. The quick start function is described in the VW manual:
Quick-Start Function
To allow the engine to be started quickly, the Diesel Direct Fuel Injection Engine Control Module J248 evaluates the signals generated by the Camshaft Position Sensor G40 and the Engine Speed Sensor G28. The Diesel Direct Fuel Injection Engine Control Module J248 uses the signal that the Camshaft Position Sensor G40 generates to determine the relative positions of the pistons in the cylinders when starting the engine. Because there are two gaps on the crankshaft sensor wheel, the Diesel Direct Fuel Injection Engine Control Module J248 receives a usable reference signal from the Engine Speed Sensor G28 after only half a turn of the crankshaft. Cylinder 1 Cylinder 3 Cylinder 4 Cylinder 2 By interpreting the signals from these two sensors, the Diesel Direct Fuel Injection Engine Control Module J248 determines the position of the crankshaft in relation to the camshaft and thus the positions of the pistons in the cylinders at an early stage. With this information, it can activate the correct solenoid valve at the proper time to initiate the injection cycle in the next cylinder to reach the compression stage. The quick-start function enables an early engine start because synchronization with the first cylinder is not required.

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Hello Steve! I have the same issue with an AXR 1.9TDI. I am interested in following your post and maybe find an answer for this problem.
Until now I tried adjusting the camshaft synchronisation angle, now theengine is at +0.6 degrees KW. I read this on measuring block 004 in VCDS.
On the other hand, in measuring blocks 005 , the start synchronisation is 1.0, wich means the synchronisation of camshaft and crankshaft failed.
right now i don't know what to do to synchronise them...
 

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Discussion Starter #3
Hello Steve! I have the same issue with an AXR 1.9TDI. I am interested in following your post and maybe find an answer for this problem.
Until now I tried adjusting the camshaft synchronisation angle, now theengine is at +0.6 degrees KW. I read this on measuring block 004 in VCDS.
On the other hand, in measuring blocks 005 , the start synchronisation is 1.0, wich means the synchronisation of camshaft and crankshaft failed.
right now i don't know what to do to synchronise them...
Hello Emi,
Thanks for the information. I can only suggest that you might try asking a friend that has access to a dual channel oscilloscope to take a look at both waveforms while it's running. This can be accomplished by inserting a paper clip into the pulse output of both plugs leading to the car's computer then attaching the scope probe to each paper clip. If you look at the Volkswagen drawing above the scope trace in my original post you can see that the first pulse of the camshaft is always on the third crankshaft pulse. This picture shows that mine are synchronized the same. Maybe in this way you can adjust your camshaft until it lines up with the drawing.
The only other idea I had for my problem was to run the car until it is at operating temperature then unplug the engine coolant sensor G62 or the fuel temperature sensor G81 to see if the engine cranks any differently after warmed up. Each of these has an impact on the quantity of fuel injected. I have also attached the manual that I came across explaining the 1.9L engine. Hope this helps.
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Discussion Starter #4
Hey Emi,
May have found the last piece of the puzzle, going to wait a week to see if I can get repeatable results. Make sure you check these:
1. Good lift pump
2. Good fuel temperature sensor
3. Good cam sensor
4. If all of these are good then raise your back seat so that you can hear the lift pump in the fuel tank. If it only runs for one second when you turn the key to the position that all of the indicator lights come on, cycle the key 5 times to let the pump pressurize the fuel loop to the injector pump. When you are cycling the key leave it on long enough to hear the lift pump stop then cycle it again for 5 times then start the engine. Results are promising.
 

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Discussion Starter #5
Well I haven't given up on this, just work on it when I have the time. To date I have replaced these components all from the local VW dealer but still have the same issue:
  • battery
  • lift pump, filter and check valve on the filter
  • cam position sensor
  • coolant temperature sensor,
  • fuel temperature sensor
  • installed a no return check valve in the fuel supply line (2 psi cracking) between the filter and tandem pump
  • checked the fault codes with a VAG my mechanical engineer colleague and good friend (Jim) has, none found. He grew up troubleshooting and rebuilding diesel engines in his dad's big rig shop, he is just as puzzled as I am
  • installed a pushbutton to activate the lift pump for a few seconds before starting, somewhat improved but still a long crank after the engine is hot.
  • measured the tandem pump pressure at the fuel return port, found that the check valve in the return line is bad. Pressure at idle is 50 psi not the 15 psi stated in other posts. Pressure fell off to zero after stopping engine. Installed a hand valve in the return line to trap pressure when the engine is turned off. No difference. Looking at replacing tandem pump, we are both believe it's possible since the cv is bad then the pump vanes and possibly the high pressure cv in the pump may be going out also.
  • Will try recommendation in other posts to unplug the coolant temp sensor after a run to see if it cranks in two strokes. Might indicate a software mistake VW had on earlier models with warm start injection timing when the engine is hot.
  • All advice is welcomed.
 
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