Saab: car wont start, vacuum leaks, electronic control unit

Question
QUESTION: Jerry,  I have a saab 87 900 it runs fine but it will set at night and will not start in the morning then it will just fire up with no problem. would this be a relay problem?

ANSWER: Jimmy:
 I don't quite understand the problem as described. Did you mean that it won't start when cold? Can you re-send a more detailed description please.
 Generally, though, problems involving hard starting at cetain times involve sensor failures somewhere.
I'll wait for your reply.

         Hope this helps,
         Jerry

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

QUESTION: Yes when it is cold.  I can drive it all day start and stop with no problem but if it sits over night with 30 degree wheather it will not start until it warms up.

ANSWER: The cold condition hard starting problem is in order of lilkihood:
(a): A vacuum leak
(b): A defective cold start sensor
(c): A defective automic idle control (aic)
(d): A poor electrical connection(dirt, corrosion, etc) or a bad electronic control unit(ECU)
 

 As a first step, I would check for vacuum leaks...an easy way is to spray carb cleaner/starting ether around all vacuum connections and observe if the engine speeds up when so doing.

         Hope this helps a bit,

         Jerry

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

QUESTION: Jerry, thanks so much for all your help.  Now it did the same thing when the car was warm.  after overnight sitting it is running fine again.  Could it be the fuel pump? When it would not start I checked the coil and fire is going to the ignition.  If it does it again I will check the fuel rail and keep  hoping I find the problem

Answer
It could be the fuel pump..an unusual set of symptoms, but possible. Fuel pumps fail typically by "losing voltage sensitivity", that is requiring a higher than usual voltage to run. When starting, the mains voltage can drop to 10.5~11. volts, due to starter load, especially under cold conditions. A 'tired' fuel pump may not run at such voltages, as they would have when new. A good way to check is to "hot-wire" the fuel pump directly from the battery to the pump's positive terminal (after removing the existing one temporarily)using a loooong jumper wire. Allow the pump to run continuously just before trying to start...if the engine starts, then..... you got it! (the pump).

         Jerry