S1 Exige won't crank

Couple of weeks ago I replaced the duff battery with a new one. Took car for a blat and everything seemed fine.
Yesterday car refused to start, but would bump start.
Lights come on on dash, pump primes but engine will not crank (not even a solenoid click).
First thought it was earth, but full beam doesn’t dim when trying to crank.
Next suspect was starter/solenoid.
Today took out started and checked everything. Starter turns as designed and so does solenoid (throws out bendix).
Next checked the relays behind driver seat first by continuity test and then by swopping around. So relays are fine.
Tested steering wheel/ignition switch. Car will crank and run if jury lead is taken from steering wheel/ignition switch (black wire) straight to solenoid.
This seems to suggest the immobiliser could be the cause of the problem.
By the way this is an Audi Exige so it uses the Emerald CPU.
Any ideas or suggestions?
Thanks.

85 views and not a single word of advice.

So, what do you think is going to happen to house prices?

Yeah but your car is unique, mate, that’s the reason

Daft question, I suppose, but have you had a word with Bernard?

I’m asking about my Exige not the Esthi(which is purring along). Have done everything Bernard has suggested. Still no further.

Okey, dokey, didn’t realise you had both.

Hi,

I know this might sound too obvious but I had this exact same problem, checked everything and all seemed to be ok but on a second look it WAS indeed a bad earth, might be worth DOUBLE checking that it is fastened tight, mine was loose and thats what caused the problem, tightened it up and hey presto, started first time!

Good Luck.

Ken, the immobiliser is suspect, the same happened to mine before I took delivery and they had to bypass it.

85 views and not a single word of advice.

So, what do you think is going to happen to house prices?

Ken - I guess most of us are not familiar with the Audi conversation to offer specific advice and you appear to have traced all the generic potential problems.

Can’t see it being the immobilser though if it will bump start. That seems to suggest a starter issue; and as you appear to have bench tested it successfully, then it only leaves a poor earth which I think has already been suggested. If the earth off the lights is a separate one then you may hav incorrectly ruled it out when you sais the lights didn’t dim?

No, I vote for the imobiliser. Steve, the imobilisor will isolate the starter solenoid, and bump starting negates the need for the starter motor at all. Normally the imobilisor would also isolate the fuel pump, but this is totally dependant on who wired up the conversion.

Does it still use the standard imobilisor? If so this has two quite seperate isolation circuits, one for the starter solenoid the other for the fuel pumps and one circuit can fail (it did on mine).

If it still uses the standard imobilisor, it is quite easy to get around, send me a PM and I will let you know.

Sean…