Intermittent glow-plug function on Golf Mk3 '95 TDK

[$hitblast]

Well, after changing the glow plugs and fixing the leak in the diesel pump, the car ran fine for a couple of weeks.

Then it quit glowing, and needed half a minute of churning in the middle of summer to get startet. The glow plug light would light up as normal for about two seconds, then start blinking. No voltage on the bus bar, 12,7 v beneath the glow plug relay. Relay clicking as usual on startup.

I pulled out the 50A fuse to check it. After the mechanic fixed the glow-system last time, he shorted the fuse with a standard screw. The fuse with the screw looked just fine, but felt hot to the touch. I put the fuse back in, and for some reason, the car now started just fine a couple of times, before reverting to hard to start and blinking glow plug indicator. I immediately after trid to pull the fuse again, to redo the trick, but it was now so hot, I could not bear to touch it. After a little while, I reinstalled the glow plug fuse, and the car started as normal again.

Two days after that, the brake warning-light would come and go at odd times, with no relation to braking.

No error codes, but there is no sensory for the engine on this model. Only ABS, airbag and immobilizer. Immobilizer reports faulty wiring, though.

Any ideas?

[Idle]

If a 50A fuse is getting too hot to touch, there's a problem on the delivery side — something is leaking current to ground, would be my guess.

A fuse shouldn't ever be more than mildly warm, if that.

That's probably why your glow plugs aren't getting hot enough — the current that should be heating them is going elsewhere.

Might also be another faulty plug.

[gldgti]

Might also be another faulty plug.

+1 for that

[$hitblast]

So, a broken plug can short the system?

[Idle]

If it's broken where current can leak to ground, yes.

If it's a dead short, of course, the fuse will blow — that it's only getting too hot suggests leaking through a resistance of some kind, which could well be a faulty plug.

Incidentally, the person who replaced the 50A fuse with a screw (if it wasn't merely a resistance that looked like a screw) wouldn't be a mechanic, but a butcher...

[gldgti]

The plugs are already low resistance elements. Normally about 3 ohms IIRC. Normally when they fail the resistance goes very high, but its not impossible that one could short somehow, particularly if there are other problems with the engine. From your other thread, I suspect your injection timing could be doing crazy things, which might have overheated a glow plug (the injector sprays directly at the glow plug in the pre-chamber) and in that case anything might happen.