3.0 TDI Starting Issues: Troubleshooting Guide

Hello!

I noticed that on my uncle's 2007 A6 3.0 TDI (ASB, 171 kW), it seems to have some kind of automatic start function.
Insert the key, turn it without needing to hold it, and the rest is handled by the electronics.


However, this automatic start function waits for a moment during the start-up process before starting the engine. Approximately one second.


On my A4 (also known as ASB), without this automatic start function, it also only starts if the ignition has been on for a while.
If I insert the key into the ignition and immediately turn it to the "start" position, the engine cranks for about the same amount of time that an A6 takes before starting.


Why?
Does the MSG need to "boot" first?



Sure, here's the translation:

"Thx."
Michael.

No, don't boot, don't preheat .

"My BPP also has this issue in the A6, and I didn't realize it at first. Then I removed a glow plug, plugged the hole with something else, connected the ground, and tried to start it."

Since they are ceramic candles, they ignite very quickly, and the tip becomes hot within a second. Then, and only then, does it start to work. And all of this happens even at temperatures around 40°C (I haven't tried it at higher temperatures).

I think I know the reason for it, but I'm not sure if it's actually due to that.

For CR (Common Rail) engines, this is perfectly normal, as the pressure in the fuel rail needs to be built up first. The time it takes depends on the condition of the high-pressure pump and the intake system (filter, pre-pump, etc.).

Best regards,

No, I'm not talking about the second hand on a clock, but the "waiting second," when you turn the key and wait for the starter to engage.

It's annoying because you can't turn off the engine at a red light if you're the first in line, because then you just end up not moving for ages. Or it's great when you've accidentally stalled the engine. Even though it's warm, nothing happens.

It's quite possible that they also need to be preheated, I'll have to try that out.

michiglaser wrote:

Hello! However, this automatic start function waits for a moment during the start-up process before starting the engine. Approximately one second. Why?

Even in direct injection car engines, pre-glow is still commonly used, even with a warm engine and high ambient temperatures, because it improves exhaust quality and cold start performance.

"Correct! Numerous engines continue to be preheated for a longer period even after the engine has already started. While the preheating power is reduced via PWM, the preheating process still occurs. This also serves to improve the exhaust quality during the warm-up phase."

I noticed this on a 1.3 CDTI (also known as 1.3 JTD or 1.25 DDIS). As long as the coolant temperature was below approximately 70 degrees Celsius, the glow plugs were operated with a reduced current. The downside was that the original glow plugs had to be replaced after two winters, which was still within the warranty period (3 out of 4 were defective, and the cost was split 50:50 as a goodwill gesture because glow plugs are considered wear items).

Okay, I took the time to check my BPP (2.7 TDI) today.

The glow plug threshold is 41/42°C coolant temperature for the preheating phase. However, afterglow is only activated at temperatures above 8°C.

Control unit: 4F0907401B
Software version: 377319

1.4 HDI eco (Euro 4, 5 l fuel efficiency class):

- Pre-glow threshold: The system activates based on a combined value from coolant and intake air temperature, below approximately 35 degrees Celsius (with 100% power for 180 seconds, briefly shutting off to save power during startup after the glow plug cycle completes in the instrument cluster).

- Afterglow threshold: Coolant temperature below ~50 degrees or intake air temperature below 10 degrees (with PWM control, adjustable in four steps from ~10% to 70%).

Source: PSA repair manual for 1.4 HDI eco engines (from model year 2005; the present edition, as of 2007, describes a Citroen Berlingo).