Starting problem when warm - troubleshooting

[zagato64]

Hi,

I have a 99 Carrera US model with 74k miles (30k on the motor).

Here's my problem:

- It will not start when it has warmed up.

- The motor turns over just fine but it does not start at all, not even a sputter.

- After letting it cool for 15 minutes it starts right up.

I thought maybe the plugs were worn so I replaced those and threw in a new air filter. This didn't help at all.

I suppose I need a diagnostic tool to hook up when it's not starting but I don't have one, Any recommendations on an ODB tool?

Are there any troubleshoot steps I can take or likely suspects?

Thanks for the helpful forum.

Tim in Santa Clara, California

[Loren]

Use Durametric software on a laptop to do diagnosis.

Sounds like a car I recently had where the crankshaft position sensor would get hot and open up. When the CPS is open (or not present) the DME thinks the engine is not turning over so it never turns the fuel supply on.

There should be a fault code there when you have the problem - but perhaps not when the engine is cool.

[zagato64]

Use Durametric software on a laptop to do diagnosis.

Sounds like a car I recently had where the crankshaft position sensor would get hot and open up. When the CPS is open (or not present) the DME thinks the engine is not turning over so it never turns the fuel supply on.

There should be a fault code there when you have the problem - but perhaps not when the engine is cool.

Thanks for the quick response,

The CPS was next on my "shotgun" approach list. Where is the CPS located?

[Loren]

On the clutch/flywheel bell housing.

I still suggest a code reader (to confirm) so you don't needlessly replace parts.

[txhokie4life]

CPS failure doesn't always flag codes.

mike

[JFP in PA]

True, but an OBD II scanner that captures PID data (real time sensor data) will see a questionable CPS that has not thrown a code......

[zagato64]

I hooked up an OBD scanner but got no codes. I went ahead and ordered the flywheel sensor. Hope that works.

Thanks for the replies.

Tim

[Loren]

You can easily test the sensor.

Remove connector. Connect ohmmeter to CPS connector, pins 1 and 2.

Display at 20 °C: 0.8 - 1.0 k ohms

Connect ohmmeter to CPS connector, pins 1 and 3.

Display: infinite ohms