Expert: autohelp - 3/5/2010

Question
QUESTION: My 96 STS has started requiring long cranking time to start when the engine is warm from previous running. Cold start is normal. No check engine light. Suspect a sensor (temperature?), but have no idea beyond that.

ANSWER: IS or HAS the CHECK ENGINE light on the dash ever illuminated ?.

---------- FOLLOW-UP ----------

QUESTION: As stated, no check engine light. Light working, as it illuminates with all other dash lights when ignition turned on.

Answer
Temp sensor plays NO role in the starting of the engine when engine is already at normal operating temp.

Possibilities are:

1. Leaking fuel injectors causing pressure drop.

2. Faulty 2 second fuel pump relay not coming on to pressurize system prior to engine start.

3.  Faulty fuel pump check valve in the fuel pump causing fuel from the fuel line to empty fuel back into fuel tank.


Try turning the ignition to the ON position and back to the OFF position 3 times prior to starting the engine and see if problem is resolved.

Here is a test procedure to see if the fuel pump works when your problem occurs.

1. Remove the gas cap.

2. Listening very carefully with your head out the door and getting as close to the ground and listening at the gas tank.

3. Turn the ignition switch to the ON position ONLY, Do NOT try and start the engine. You should be able to hear the electric fuel pump motor run for only 2 seconds and then it will stop.

4. If you can hear it run for the 2 seconds and then stop, You do NOT have a fuel pump problem.

5. If you do NOT hear the fuel pump run for the 2 seconds and then stop, Then you have a faulty fuel pump relay or a leaking fuel pump check valve failure and requires fuel pump replacement