I've got a bit of a problem with my VW T4 Transporter van, 51reg with a 2.5 102bhp TDI. It starts fine but will only run for a couple of seconds & then stops. It did this a couple of weeks back & I thought I'd sorted it when I found some slack terminals for wires that feed the dash at the battery. Now the problem is back. The heater plug light doesnt come on at all & the airbag light is on too, if the heater plug light comes on then it starts & runs as it should.
The van has been stripped right back for a respray, glass, trim, dash, the lot. It's on it's way back together now & this problem has started, I'm thinking it's likely something I've done but havnt found anything yet.
Any ideas welcomed.

Sounds to me like an issue with the immobiliser, a classic problem is the inductive loop around the key barrel failing to read the key. make sure the cable to it is ok.

The only other suggestion is borrow a fault scanner, it will tell you in seconds

Is everything back on the van ( ps I not an expert ) but to me sound like somthing is electrical is not connected ( impact sensor ).

Was the respay after an impact ?

another thought Has there been any welding done on the van did you disconect the ECU.

regards

Agriv8

When the van was low baked, were the keys in the ignition?

The immobilizer is a fair bet too, neither key will start the van so I'm thinking the chip in the key is ok.
The van did have a little damage but it was just panels that needed knocked back straight & filled, the respray is more cos I dont like AA yellow as much as the blue it now is
I dont know about the keys being in it when it was baked but it's been running a fair bit without fault since then so that shouldnt have made any odds.

do know much about the t4's but on the older t25 diesel the was a fuseable links on the glow plugs

will be inside a little box were the glow plug timer relay is

try going here someone will know


http://www.brick-yard.co.uk/forum/default.asp

sounds identical to a fault i had with my petrol car and the keyfob.

Basically the engine would start, run for 2 seconds and then die. The way security worked is once the extra fuel was injected for startup the immobiliser would go "oooh, key's not programmed to this ECU" and cut the engine.

We inadvertantly gave several VAG ECU's frontal lobotomys before we realised what was going on. If the keys are in the ignition when the car/van is baked then it can put the ECU into limp mode and needs a reset to clear the fault codes

I had the problem with the loop reading the key on my Audi, i ended up cleaning the contacts to loop and it worked again.

I'm not sure on the van, but try shaking the steering wheel and trying again, maybe a bad connection.

I have Vag-com but I suspect I'm a little to far away to help

Cheers for the replys folks, looks like I'll have to get my mate out with his diagnostics to see if that'll tell us what's up.
MikeR's theory sounds most plausable, the T4 uses the same type of ring around the ignition barrel as other VAG stuff
There's forum just for the T4 & I've asked there too, most common thought is the immobilizer.
I forgot all about that little fusable link, old Caddy diesels had them too. I'll have a look to see if there's anything similar, it'd be nice to find a simple cheap fix cos I've already bashed a door pushing it around so it's cost money that way already