WEIRD start problems????

[Guest]

still having trouble with a 911 supersport 3.2


these are the problems...really have been scratching my head over this one...
here goes.....

1) It will start fine when cold and will run perfect...does not miss a beat

2) when you stop it will start straight away and will start repeatedly but if you wait for approx 1 minute it will not start (checked for a spark and it has no spark) -seems there is a time issue on a control or a sensor??

3) when it does not start you are able to bump start it and it will run???

initial thought was the immoboliser...this has now been removed as the 1st process of elimination

also checked all the feeds and resistance reading at ECU unit...this seems fine

I would really appreciate some help here!!

very very desperate for some response

thanks

 

[Guest]

Have you replaced the temperature sensor at the connector block with a resister as Lawrence suggested. I found measuring the resistance of the sensor was pretty futile as the failure can be dependant on heat/vibration etc..

I carried a resistor around with me (with two little connectors soldered on so I could plug it in) and when the car wouldn't start I replaced the sensor with the resistor. This was the only way I could eliminate the sensor in the end.

Cheers

Andy

 

[Guest]

nice one....however, where is the sensor exctly located....I can find the connector near cylinder 3

cheers

 

[Guest]

The sensor is in cylinder head 3 but thats not what you replace when testing.

As you look at the engine look to the left of the 2 left inlet manifold pipes furthest from you. There is a mount which holds 3 connectors. The top connector is the cylinder head temperature sensor. The part in the mount (should be white) goes to the sensor (measure across the two pins when checking resistance of the CHTC), the part that plugs in goes to the ECU.

When the car won't start you need to bridge the pins in the connector that goes to the ECU with a resistor (you'll need to solder connectors/pins on the resistor legs to do this). A value of 300 ohms will tell the ECU the engine is at around 90 degrees C and should fool it enough to run.

If after a few no starts doing the above starts it I would say its likely to be the CHTS.

I would add that point 3 on your post makes me unsure as to whether it is the CHTS but the above is an easy test so worth trying.

Cheers

Andy

 

[Guest]

Does it actually turn over when you try to start it? Could be starter motor if not..... My 200SX used to behave in a similar manner and that was down tot he starter motor.

 

[Guest]

yeah it turns over but no spark

 

[paul kelley]

Hi

Have you checked the coil? This proved to be the problem with my car (1988 SS cab) Have not had any further problems since replacement in 1992 (thats the kiss of death then!)

Hope this may be of help

Paul Kelley

 

[Guest]

thanks alot for the response........there is only one terminal in the top connecter on mine...I assume this sensor is earthed through the engine block and the resistace goes down the one wire???

I have made a short wire that I can plug in but I can only think that this will need earthing?

 

[Laurence Gibbs]

This sensor will not cause a no spark situation. It will make the car "harder" to start but will not stop the engine firing. A resistance test with a multimeter is the best way of testing a NTC type temperature sensor. replacing the sensor with a fixed resistor will force the ecu into a "limp home " type mode.
No spark can be caused by a number of factors Coils, distributor caps etc. Also if you have a flywheel sensor check that you are getting the correct pulse (also check for correct fittment). It sounds almost as if when the engine is cranked using the starter motor that this causes too much of a current drain on the cct and the car will not fire. Bump starting obviously by passes the starter motor and you have enough "juice" to start the car up. just my view from the arm chair.
By the way it may be the way I read it but I did not suggest by passing the ntc with a resistor.best way to test is with a multimeter.

 

[Laurence Gibbs]

The following are for a 964 NTC sensor the values may be different for a 3.2 Carrera
0*c =4.4k ohms -6.8k ohms reducing to 100*c =160-210 ohms i.e. 4k cold apprx 160 ohms hot. In practice often there is no variation in temp hot or cold when this sensor fails.

 

[Guest]

I had a similar problem on my 1988 Supersport. I found it was one of the relays in the "boot" on the driver's side under the windscreen. For some reasons numerous of my relays began to fail together over a 9 month period. I have since replaced three in that location and the relay under the passenger seat. Since then, no starting or running problems- touch wood!!