No power after battery replacement

Hello everyone,
I was having cold start problems with my 1Z engine (it took 4-5 seconds of cranking), and after going through the entire troubleshooting process, including checking the crankshaft position sensor, fuel injectors, spark plugs, and performing various tests. It turned out that replacing all the cables revealed that the problem was obviously caused by a different battery.

"This weekend, I borrowed a battery from an A4 110PS TDI and installed it. I haven't had any starting problems since two days ago."

BUT: the 110 hp TDI has been modified with a tuning module, and it has been like that since then.
The battery replacement process is the same as for a standard 110 model, at least initially.
Even sputtering and black smoke.
My old battery will last for one more week in the 110.
What's going on here - is it possible to replace the battery in a TDI engine that has been modified with a tuning module?
Don't disconnect?

I am grateful for every tip.
Horstl.

Quote:

...What's going on here - is it permissible to replace the battery in TDIs that have been modified with a tuning module? Do not disconnect?

No, either you damaged or disconnected the connector/cable to the ESP, or the effect is just happening coincidentally at the same time as the battery change.

Best regards, Rainer.

Horstl wrote:

BUT: the 110 hp TDI has been modified with a tuning module, and it has been like that since then. The battery replacement process is the same as for a standard 110 model, at least initially. Even sputtering and black smoke. My old battery will last for one more week in the 110. What's going on here - is it possible to replace the battery in a TDI engine that has been modified with a tuning module? don't disconnect?

Hi Horstl,

As far as I know about the electrical systems of VP-TDIs, the entire fuel injection system is essentially de-energized as soon as the "ignition" is switched off.

A power connector doesn't detect if the battery is disconnected.

I suspect you might be experiencing contact problems with the old battery. Then, various interference peaks can occur, for example, in the plug, and disrupt its function.

Incidentally, other onboard electronics may also malfunction or even be damaged.
So, please quickly check what's going on .