troubleshooting a taurus

[David Doddek]

>mike wrote: 
>
>>...
>>The taurus has a very hard time starting after sitting overnite or 
>>over perhaps 8-10 hours.  Takes a large amount of cranking with no 
>>firing, then stumbles slowly to life.  Ambient temperature doesn't 
>>seem to have any effect.  Computer reveals no fault codes, pump and 
>>filter are good.
>>
>>Isn't there a fuel accumulator which should maintain fuel pressure 
>>when sitting?  If this was faulty would it allow pressure to drop - 
>>forcing the pump to charge the system again before it could start?
>
>No accumulator, it needs to be a leak-free system, for obvious reasons.
>It does sound like fuel pressure has gone away.  Assuming this is a V6, 
>(you don't say, and you don't even say what year) there is a Shrader 
>valve near the front where you can measure fuel pressure.  It should be 
>35 psi at idle, and about 25-30 after sitting.
>
>Turning on the ign should cause fuel pump to run a couple of seconds, 
>then stop.  Try switching on and off once or twice before starting to 
>see if that helps.
>
>EFI in my '86 Sable V6 has been almost flawless in 115K miles.  Had to 
>correct a weak idle recently by de-coking the air bypass.
>
>RD
>
If you have a fuel problem, then it would not run or start hot.  The fuel
will pressurize in a few seconds from zero pressure and the engine will not
always hold pressure for a long time.  It does not have to.  My car looses
all pressure in a matter of minutes.

The problem sound like a cold starting problem, ie cold engine ie not hot.
A cold (ambient) engine requires extra fuel to start until the cylinder
surfaces get hot.  Takes about 3 minutes on an average day.  A little longer
in the winter.  The computer detects this by measuring the engine temp with
sensor and giving the engine extra fuel.  Try changing the engine coolant
temp sensor.  It sounds like it has failed to a level that does not trip the
diagnostics, but gives the computer a false signal making it think the
engine is hot and thus gives it no starting enrichent.  This is why it still
starts when it is warm.

David J. Doddek                                          |pantera at pobox.com
Owner SGD Electronics & Development Engr for Caterpillar |h 309 685-7965
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