Wont start after a short stop

[Stan the Bat]

Car refuses to start after a short stop. eg to fill up etc.

If left for more than 5 mins then starts with no problem ..

Car is a Saab 9.3 Aero.

[GreenV8S]

Heat soak causing fuel vaporisation or an electrical/electronic failure? Conventional troubleshooting techniques should track that down for you.

[stevieturbo]

Shout really loudly at it

[CorradoTDI]

Stan the Bat said:

Car refuses to start after a short stop. eg to fill up etc.

If left for more than 5 mins then starts with no problem ..

Car is a Saab 9.3 Aero.

What exactly does it do / not do?

[Stan the Bat]

CorradoTDI said:

Stan the Bat said:

Car refuses to start after a short stop. eg to fill up etc.

If left for more than 5 mins then starts with no problem ..

Car is a Saab 9.3 Aero.

What exactly does it do / not do?

Drives normally, but if the engine is turned off for any reason then wont start until about 5 mins have passed.
Just cranks but doesn't fire.

Has been in local garage a few time now, they have changed the fuel pump twice without success.

[Stan the Bat]

stevieturbo said:

Shout really loudly at it

Not my car, but belongs to the wife of a friend of mine.

[guards red]

If it cranks normally, that the starter motor turns the engine, would think about the crank position sensor.

If it doesn't spun then the starter.

[davek_964]

Years ago, I had a car that would start instantly when cold, but was often very difficult to start when warm / hot. It would spin the starter motor, but just didn't catch.

After I'd owned the car for a few years, the starter motor started failing - sometimes wouldn't turn over, so was replaced. The hot start problem never happened again. It had always sounded like it was turning the car over normally (same as when cold) but for some bizarre reason a new motor completely solved the problem.

Never really understood why!

[EmailAddress]

Coilpacks.

[320touring]

guards red said:

If it cranks normally, that the starter motor turns the engine, would think about the crank position sensor.

If it doesn't spun then the starter.

I'd echo this, or possibly a temp sender being faulty if the car smells rich once warmed up

[GreenV8S]

Check the state of the fuel and injection systems while it's cranking but not firing. Has it got a good spark? Is fuel being injected?

[Stan the Bat]

Thanks chaps, will pass these suggestions on.

[Stan the Bat]

320touring said:

guards red said:

If it cranks normally, that the starter motor turns the engine, would think about the crank position sensor.

If it doesn't spun then the starter.

I'd echo this, or possibly a temp sender being faulty if the car smells rich once warmed up

What temp sender would do this ?

[Stiggolas]

Definitely crankshaft sensor. i had this and diagnosed by squirting it with cold water when the car didn't start. The car never cut out but failed to start when hot.

[Evanivitch]

There's definitely no hesitancy in the cranking? Hot soak on the starter motor would make MX5 hard to start after a refuel. Usual sign of starter motor solenoid imminent failure.

[fatjon]

Did these not have nikasil liners? If so a compression test might reveal that the cold bores when wet with fuel have almost zero compression. Cold they are happy, hot they are happy, coldish and a restart is all but impossible.

Had a jag v8 with this problem. The pre 2000 ones were well known for it.

[oakdale]

The CPS would be my best internet guess (as others have said), it would certainly be first on the list for me.

[E-bmw]

fatjon said:

Did these not have nikasil liners? If so a compression test might reveal that the cold bores when wet with fuel have almost zero compression. Cold they are happy, hot they are happy, coldish and a restart is all but impossible.

Had a jag v8 with this problem. The pre 2000 ones were well known for it.

Unfortunately "cold-ish" is not the issue the OP is describing & 5 min to cool down wouldn't be significant enough time if it was the issue.

[camel_landy]

From your description, my money would be on a lack of spark and as it's across all 4x cylinders, I'd be looking at the sensor.

Initially, just try cleaning up the connections (while there, clean the earth straps too) and then probably look at swapping out for a new one.

M

[Heaveho]

The only experience I've had of something very similar was on a Corrado VR6 and it was a dry joint in the fuel pump relay.