1989 740GL 2.0L Auto. Intermitant problem

After a short journey I try to start the car and it won't start. There is no spark at the plug. If I leave it for 1/2 hour it starts. Sometimes it will start and then cut out after a few yards. This seems to happen mainly after the first short journey of the day. It appears to run ok once the engine has warmed up completely.

The common cause of this seems to be failure of the Hall Effect sensor in the distributor or the flywheel position sensor in the top of the bell housing depending on which your car has.
If there are any low tension wires (apart from the HT leads) coming
out of the distibutor you have the Hall Effect system.
The cold start system is an electrically operated fuel injector on top of the inlet manifold this is operated by the temperature/time switch under the manifold
For an explanation of how this works see the page index on this site`s home page for the page on K Jet injection.
The trouble could also be caused by a faulty fuel pump relay.
Colin.

[sheerwater]

Agree with hall sensor. Annoying problem often temperature related,i.e. a specific temperature range which if it gets through it keeps running. If it stops its a case of wait and cool down. Cheers Nigel

Thanks Guys
The distributor has a LT connecter at the base, I guess this must be the Halls sensor you are refering to.
The problem seems to be getting worse, when the problem happens there is no spark. If I pull the fuel pump relay out and then turn the engine over there is a spark. I am assuming I can rule the relay out.
Dealer price for a new Halls sensor is £70, need to get it right. Apparently there is another part of the sensor which sits in the housing, does anyone know if this also needs replacing.
Does anyone know any cheap scrapyards, just phoned one who wants £85 for a distibutor.
Thank Graham

Graham,
I don`t think this does rule out the relay.If the spark returns with the relay pulled out, it seems to me that the relay is the problem.
There is a connection from the negative side of the ignition coil to the relay so that the fuel pumps only run when the engine is turning and you have a spark.
If this were to be earthing the coil connection this would be the same as a permanently closed set of points on an old style ignition system, ie no spark.
Personally I would try a fuel pump relay first, you can get one from
www.eurocarparts.com
for £18.51 + VAT and it`s a handy spare part to have anyway! (they do fail)
If you have to replace the Hall sensor, it is reputed to be a bit tricky to do,(rivetted in and has to be drilled out) so you might be better off with the S/H distributor, you should get a rotor arm and cap for spares with it!
Colin.

Peter
Quoted about £50 for fuel pump relay at dealer, seems cheapest and easiest option to try first.
The problem only seems to occur at some point between a cold and 75perc hot engine, once the engine is fully hot the fault does'nt appear.
I presume if the relay is faulty, when it happens again I should be able check for voltage at the coil.
Not very good with electrics (Mechanical engineering background).
Thanks Graham.