Mk3 Golf TDI - Cranking, but not starting- Blowing a fuse?

[320touring]

Hi, currently looking at getting a mk3 TDi beater for a daily

got one nearby that is cranking over ok, but blows Fuse 15 (engine electronics, according to the fusebox) as soon as the engine fires.

Has anyone experienced this?if so, what was causing it, and is it an easy fix?

thanks

[Rusty94cx]

It's a dead short in the wiring somewhere. Look for frayed wires or something that has rubbed or burnt against the frame or exhaust. Good luck it'll be easy or a nightmare to find.

[320touring]

Originally Posted by Rusty94cx

It's a dead short in the wiring somewhere. Look for frayed wires or something that has rubbed or burnt against the frame or exhaust. Good luck it'll be easy or a nightmare to find.

excellent, thanks!

I think it may be something to do with the circuit for the Glowplugs- although I'm not too hot on diesels!

[AndrzejM]

Correctme if I'm wrong but as I understood fuse #15 blows the moment the engine is starting. Right? So IMHO it's not related to glowplugs because fuse would blow the moment you turn your key into ignition. Then glow plugs are starting to work. I'd need to see the electrical diagram of that car to tell you more. I'll try to find it.

[Rusty94cx]

What engine electronics does an old diesel have? Mechanical injection pump only starting circuit and glow plug heaters. Had a diesel Volvo same engine but extra cylinder 6 not a 5.

[Honda100]

Voltage regulator. Once the engine fires up (spins the alternator faster) it over charges and overloads the circuit.

That's my thinking.

[user removed]

Disconnect the glow plugs and crank it, see if that keeps the fuse from blowing. The old pre 82 Mercedes diesels had wire loop glow plugs. When the injector spray pattern was bad the fuel would spray on the glow plugs and burn the wire loops in half. Benz went to pintle type glow plugs which eliminated the problem, but the cause was not the glow plugs but the bad injector pattern and the DESIGN of the glow plugs.

If you unhook the glow plugs only it should either blow or not blow the fuse. If it does blow the fuse you know it is not in the glow plugs themselves but somewhere else.

If unhooking the glow plugs and cranking it keeps the fuse from blowing then you need to pull the glow plugs and check them, or use a circuit breaker and connect them back one at a time testing each one individually.

Let us know what you find out and we can go from there. If you are blowing a fuse, then connect a test light across the shorted circuit, in place of the fuse, and disconnect the circuits sections until you kill the test light, then you have isolated the short.

regards
Mech

[mwebb]

any VW TDi has an ECM and has some electronic controls to regulate glow plugs - injection pump timing - EGR - Boost at the very least
and
the mark3 and 4 versions have problems in the fuse block that sits on top of the battery

you really need a wiring diagram to continue
a scan tool such as VCDS may point you in the right direction
or not
depending on what circuit stops working

Originally Posted by 320touring

Hi, currently looking at getting a mk3 TDi beater for a daily

got one nearby that is cranking over ok, but blows Fuse 15 (engine electronics, according to the fusebox) as soon as the engine fires.

Has anyone experienced this?if so, what was causing it, and is it an easy fix?

thanks

[320touring]

Thanks for all the hints and tips people,

much appreciated- I'll update when I know more!

[320touring]

Seller spent today working on the car..

called me at approx 2pm to let me hear it running

Appears to have been a couple of wires that had rubbed off their insulation and were shorting out..so it looks like I'll have it soon!