Audi 100 2.5TD runs for 5 seconds then cuts out..

[pxr5]

its a turbo diesel 2.5 straight five, I've run a small fuel tank direct to the filter then pump & Ive run a 12v feed to the cut out valve on the pump......this model does not have the plug in diagnostics facility....

[spink]

Originally Posted by pxr5

this model does not have the plug in diagnostics facility....

are you sure? should have 2 connections in the fusebox in the scuttle panel

ive never known any c4s with factory immo (i presume it is a c4?)

[steveb]

Ok is it mechanical injection ? ie do you have injector pipes you can loosen ? if yes, crack them at the injector and see if you get fuel there, it could have an air lock. or it won't have much fuel at all which might point you in the right direction to find out what is wrong. by the way this could get messy :-) watch out for squirts of fuel !

[John.]

Originally Posted by pxr5

Ive this early straight 5 cylinder believe its a AAT engine, this car has been standing for some time, I start it up every 3/4 months but now it starts up & dies after 5 or so seconds,

Ive a good flow of fuel to the pump. Ive fiddled with all the electrical connections but no luck so far.
I'm really stuck with this, can any one suggest whats wrong? thanks

It's not like it's a modern motor with lots going on electrically...…..but it does sound like the immobiliser kicking in, if it has one?
Does the 5-pot diesel have a cable to the pump or is it fly-by-wire?

Here's a thought though.....if it's been sitting and maybe the rings are seized in such a way that the compression is low, maybe the glow plugs are helping to aid ignition but then when they switch off the diesel being injected struggles to ignite due to low compression?

I know the above sound bizarre and glow plugs usually stay on for longer but maybe it might be worth pulling out the injectors or glow plugs and putting a bit of oil down the bores?
………..just a random thought

Whatever it is, hope you get to the bottom of it.

[vorsprung durch technik]

Originally Posted by John.

It's not like it's a modern motor with lots going on electrically...…..but it does sound like the immobiliser kicking in, if it has one?
Does the 5-pot diesel have a cable to the pump or is it fly-by-wire?

Here's a thought though.....if it's been sitting and maybe the rings are seized in such a way that the compression is low, maybe the glow plugs are helping to aid ignition but then when they switch off the diesel being injected struggles to ignite due to low compression?

I know the above sound bizarre and glow plugs usually stay on for longer but maybe it might be worth pulling out the injectors or glow plugs and putting a bit of oil down the bores?
………..just a random thought

Whatever it is, hope you get to the bottom of it.

Nice bit of lateral thinking there OB1, when my C4 2.8 had the immobiliser problem it would fire and immediately cut out so as op is saying his runs for 5 secs you could well be right!

[pxr5]

The pump is electronically controlled, which in turn is via an ECU, there ia an air flow meter too, Ive rigged up a 12v live feed to the pump solinoid cut off valve, and a seperate fuel line.
Cracking off the fuel unions at the injectors, fuel comes out, when the engine dies no fuel is at the injectors, so its the pump or the ECU etc. The key, Ive never had to press the button to start the engine, does it neeed a new battery? any way of checking the key??? thanks

[steveb]

is there a stop solonoid on the end of the pump ? if yes check the feed here, you could try putting a live to that but remember you will have to disconnect it to stop it should it start

[pxr5]

Ive rigged up a 12v live feed to the pump solinoid cut off valve,

[Sandro]

Originally Posted by pxr5

I assume it has, the key fob has a button, but ive never had to blip it to start the engine before.

It's not the alarm type, the chip is in the keyfob, gots read by "antenna" near the ignition.

Tried to read the faults?

[pxr5]

Do you think its a electrical issue, or a mechanical problem?