frustrated

swapped the LH relay yes. EZK no not yet as its at a garage so cant try that until monday.
will check Fuel pressure and pump on monday It might be over pressure?
Flex plate pressure release? hmm! will take it to Paul Anderson's if I get it going.

no the crank shaft sensor has not been changed. Not sure where that is on an 89? or do you mean the TDC or speed sensor?

Just as an add on. The car cuts out after about 20 minutes if left in park and engine at idle.
It has a spark as will often fire up again after cutting out but then dies almost immediately. until left for a while.
The hot fuel pump relay and lack of current at the pump relay from the ecu when it fails should point to something. will put a tester on the ecu terminal and fuel pump on monday to see what happens when it cuts out.

RED SHARK 1990

Its on top of the trans,you can see it after removing the maf. Its the same exact symtom i have had,speed sensor-crank sensor the same one....look on forum for removal..

928GTSM

I had almost the same problem on my GTS, it would run fine up until such time as the engine reached the top end of normal operating temperature and then die. As John Speake suggested, after all it was he who diagnosed my problem for me, you need to see if your getting a spark at the plug once it's given up starting altogether. Ignore the start/won't start phase wait until it's totally dead. Also look and see if your rev counter flickers when you turn the engine over. Once the engine got warm the heat build up in the sensor was causing a break in the circuit and it would then fail to send a signal to the relevant ECU without which it doesn't when to send a spark to the plug.
If you have no spark at the plug or your rev counter doesn't move when cranking the engine then it's highly likely that it's your crank position sensor. If it is and your doing it yourself be warned they can be a sod to get out. You have to remove your air filter, MAF and fuel regulators and have plenty of penetrating oil and a be ready to sweat & swear in equal measures, unless it's been replaced previously and it may come out easier.
Good luck with tracing your problem.:

Landseer

A couple more possibilities that have caused this behavior in other cars:

Otherwise-good CPS, but frayed wires beneath CPS connector boot.
Battery ground cable (ends shiny mirror, hidden band of grey corrosion under the plastic cover)
Engine ground cable connection (pass side, underneath, frame to engine)
Loose ground wire for engine electronics (deep in the back of the valley, hidden by fuel regulator and S4 throttle cable)


And another potential source:
Bad ground for ignition amps ( a couple of unobtrusive thin brown wires, joined by a single ring terminal, bolted to the inside of pass fender, underneath 14 pin connector)

John Speake

It is concerning that your fuel pump is so noisy. From our conversation this morning, I think the output stage in the LH that drives the fuel pump relay is being overloaded as the FP relay heats up, possibly due to a failing fuel pump. The output stage in the LH has a thermal shut down protection.

Suggest that the fuel pump is investigated.

the flyin' scotsman

Is the car a '88 or '89 model?

If '89 then check that you have an intank fuel pump? Its an easy check, just remove the cover plate for the external fuel pump and fuel filter and see if there's wires going from the external pump toward the fuel tank..........if so then you have an internal fuel pump which causes numerous issues.

frustrated

Its a late 88 1st register so really an 89 in all but name. Yes its a strange problem as when the LH output to the Fuel pump relay fails you can bridge the relay and start the car fine. and it runs ok. So as you say its either the ECU (unlikely as that is only about 12 months old) or the fuel pump which was new 12 months ago. (The external one) or one of the grounds as many of you think.

frustrated

Am really not sure if I have an internal one but am sure with a stethoscope I can check. assuming an internal one sounds like an external one when its on its way out.

KenRudd

Possible alarm issue.
Failing alarm system getting hot or shorting out and causing cutoff?

frustrated

Now thats an interesting idea! Its an aftermarket system that cuts the fuel and ingnition. I expect if that was faulty the car still would not start with the pump relay bridged but you could be right. I will check the connections.

the flyin' scotsman

The internal pump was added to the system in '89 and feeds the external pump then filter to the engine:

frustrated

Thanks, I've been reading some of the threads on them. Seems its a pig to get out. If its there its probably original as have no history of it being changed. Problem with 89's is that I cant find any info on them. my workshop manual download omits 89 for some reason.

John Speake

Your may or may not have the intank pump, you can easily check by seeing there are two wires in paralllel with the main pump feeding that output union that Malcolm supplied the photo of.

Good thought about a problem with an imobiliser system, Ken !

frustrated

Hi John. ECU is en route. You should have it before 1pm tomorrow. will check pump/pumps tomorrow and alarm. There is a local agent so can probably get him to immobilise the immobiliser ! !

928mac

I did not see where you tried a different crank sensor