VW Golf 3: Won't Start? Troubleshooting Guide.

Hello everyone,

Yesterday, my brother had a coolant leak due to a faulty water hose. We replaced it today. Since then, the car won't start. The starter seems to be working normally, but it's as if the engine isn't getting any fuel.
Using VCDS, we found the error code "Fuel temperature sensor short circuit to positive" (or ground? I don't quite remember exactly which one right now).
The measured values display a coolant temperature of 16.3°C. Another parameter, whose name is not displayed, shows an implausible value of -5.6°C. This could be related to a fault in the fuel temperature sensor.

The question is: Do the SDI engines really not start at all if an incorrect fuel temperature is measured? I would have expected that the engines would start normally, but perhaps inject the wrong amount of fuel and therefore pull less powerfully or something like that.

My brother drove about 1 kilometer with a coolant shortage (which was indicated on the dashboard). He doesn't know if the engine overheated or if the head gasket might have been damaged. However, he was able to drive the car back home normally.

Do you have any ideas about what might be causing this?

Best regards,
Karl Römer.

What kind of interface does your brother have?

Do you mean in terms of the OBD (On-Board Diagnostics) system? I'd have to check. In any case, it definitely has a modern OBD connector, but the protocols are probably older because the Golf is from 1996. So, it's not OBD2 or anything like that yet.

Please check for any broken wires in the area around the starter motor (you may need to cut open the casing and inspect each wire individually), as well as the wire terminals on all connectors leading to the fuel injection pump.

@Roemer: Could you please check with the head of the company whether we have a valid VCDS license or a support key?

@ Rüdi: wie prüft man an einem 16mm2 Kabel sinnvoll die einzelnen Adern? Insbesondere läuft lt. PoIt's the starter motor.
hg
Herbert.

So, the engine would still start even if the fuel temperature was incorrect. The amount of fuel injected and the injection timing might be wrong under those circumstances, but it would definitely start. Therefore, the cause must lie elsewhere.
There might be a problem with the shut-off valve, even though it is supposedly monitored during diagnostics.
Otherwise, simply disconnect the coolant temperature sensor (the 4-pin sensor on the water pump flange). This will cause a very large amount of fuel to be injected. Then, just keep cranking the engine, and if white smoke comes out of the exhaust, it might indicate that something mechanical has failed due to lack of coolant in the engine.

@Herbert: I'm referring to the cable harness that runs from the MSG (presumably a control module) to the engine, and in the Golf III, this is routed over the starter motor. Due to the movement, there are occasional cable breaks in that area. I have a thread from about 4 years ago about my then-daughter's Golf III TDI where this was exactly the cause of it not starting.

I've experienced the same issue with two Passat 35i TDI models.

On a friend's Audi A4 B5 TDI, there was an alternative issue: a broken wire within the insulation of the 3-pin connector leading to the VP37 injection pump.