1.9 TDI Cold Start Problem

Hello fellow forum members,

I'm reaching out with a small request for help because I'm facing a problem and I'm not quite sure how to proceed. I'm trying to provide a more detailed description of the vehicle's history, hoping that someone might recognize a connection that I've missed.

This is a VW Caddy (9K9) with a 66kW TDI engine (engine code: ALE). The vehicle has approximately 300,000 kilometers and was manufactured in 1999.
The vehicle became increasingly difficult to start as the temperatures dropped, until it eventually refused to start at all. The starter motor is turning, but the engine is not starting.
The owner initially took the vehicle to ATU, who then diagnosed a defect in the glow plug system and identified the EDC control unit as a faulty component.
The owner was not satisfied with this diagnosis and went to VW. They charged him 90€ for inspection work and said that the fuel injection pump was defective.
However, no one could say exactly what was wrong with the pump.

When the vehicle came into my possession, I performed a visual inspection and found several chafing marks on the ESP wiring harness on the vehicle side. I then repaired these areas.
Among other things, the cable for the G81 fuel temperature sensor was frayed and oxidized.
The engine still doesn't want to start, though.
Dachte das er vllt. keinen Sprit bekommt und habe die Überwurfmuttern der Einspritzdüsen alle geöffnet um zu sehen ob er einspritzt. Alvery wonderful.
I then managed to get it running with starting spray. So much for the defective ESP . When it does run, it runs great.

I then checked the error memory. There were no errors stored, but I noticed that the coolant temperature sensor was constantly transmitting a value of 63°C to the engine control unit. After researching in the technical forums, it seems that preheating at a water temperature of 60°C is no longer intended.
With the connector removed from G62/G2, it heats up for a long time and then starts again. So, the sensor was replaced, the connector was plugged in, the initial values were checked again (11°C), and I tried to start it with anticipation, but it didn't start again.
The filament briefly lights up and then goes out. When the plug is disconnected, it remains on for almost 20 seconds, and then it starts up without any problems.

I then went through all the VW workshop manuals and checked everything, including the ESP system.

Needle probe: Output (target value 80-120 ohms), actual value 92.6 ohms, within specification.
Potentiometer for rule slide (setpoint 5-7 Ohms), reading 5.4 Ohms, within tolerance.
"Live value in VCDS for the throttle position sensor: 0.7V when the engine is cold (target value: 1.3-1.9V when the engine is warm)."
Set point (target value: 0.5-2.5 Ohms), actual value: 0.9 Ohms.
Fuel temperature sensor reading: 4.6 kOhms (according to the characteristic curve, this should correspond to approximately 4°C, which would also be consistent).

I'm a bit puzzled. What input parameter does the EDC-SG still use to determine the preheating time? Or am I missing something, and is it not just about the preheating?
Unfortunately, I don't have a label file for this control unit in my VCDS software. If you need any values, it would be helpful if you could provide the measurement block (MB) and field names.

Regards,
Alex.

Hello, it's very important to check the injection timing of the distributor injection pump. The easiest way is to use VCDS and check the "TDI Timing," or you can adjust the static value using a measuring tool on the distributor injection pump.
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Hi,
Please do not use starter spray, as it is not suitable for diesel engines. It can cause uncontrolled ignition, which may lead to engine damage.
A brief preheating period is normal for the outdoor temperatures.
Besides a potentially adjusted injection timing (check!), the following might also be the cause.
- faulty glow plugs;
- Possibly faulty glow plug connectors.
- poor cylinder filling;
What are the valve timing and compression like?
hg
Herbert.

Check the fuse for the glow plugs! It should be located in a small black box with a transparent cover on the left side of the engine compartment. Please examine this fuse very carefully, as a small crack can often be difficult to spot.
If this fuse is blown, the preheating light on the instrument cluster will still illuminate, but no power will reach the glow plugs. Of course, you can also measure beforehand to see if there is power reaching the glow plugs.

Hi,
According to the report, he does preheat, but it apparently takes a very long time! That's why it's causing so much trouble.
hg
Herbert.

Check the start date of the subsidy and verify if the coolant temperature during a cold start is reasonable.

Best regards, Rainer.

It could also be a stuck mass airflow sensor (MAF). I once had this issue with a 325 td. The car had starting problems and significant fluctuations in power. I cleaned the MAF sensor, and it was fixed.

Evening, everyone.

Today, I checked the start of injection using TDI timing and found that it's injecting fuel way too early. Okay, so I need to adjust it, and then I can see how it performs afterwards.
I also measured the compression, and the results showed values between 18 and 19 bar on each cylinder, with minimal variations. I couldn't find a target value for this in the ELSA documentation. Can anyone provide any information about this?

Thank you very much for your help so far. You were absolutely right about the injection start.

Regards,
Alex.

Hi,
With pressures between 18 and 19 bar, the ALE (presumably a component) is likely reaching its wear limit. That's why this one prefers a long preheating period. The question is, where is the poor compression coming from?
- Valve timing
- Valve seats
- Blocked intake channels, possibly also the intercooler piping?
- Cylinder bores;
hg
Herbert.