My cirrus fire up but doesnt start up i have replaced the ecu but it still just fires but doesnt start

There are several things that tribute to how the injectors fire, but the ECU is what actually fires them, the pick-up inside of the distributor is what tells the ECU when to fire them.

Vacuum leak is most likely cause of failing to start when you have fuel and fire. Also the signal from the coolant temperature sensor affects the computers fuel injection amount. Could be too lean or too rich. When a coolant sensor first starts to go bad the engine will be slow to start the first time. Turn it off and it will start right up.

the scanner drops out when the power voltage drops too low.
so your 12vdc the ECU is tool low. use volt meter
to find the voltage drop point.
you mean no spark, fire is what fuel does when ignited.
and spark is first. if no spark say, i have no spark to 4 cylinders.
my guess is this.
lost DC power to ECU.
this kills spark
and loss of spark kills injection so, lost power kills injection 2 ways.
find this problem by watching spark and power to ECU.
the ECU will drop out about at 9v.
cranking the voltage usaully sags to about 11v cranking.
now you have a goal 11v min, to ECU at all times.(cept siberia)

Which engine, and what have you checked so far ?

96 Chrysler Cirrus 2.5L

Here is the firing order.1 2 3 4 5 6

Here is a link of a site if you need.

http://autorepair.about.com/library/firing_orders/bl-fo-5195.htm

Good luck

crankshaft sensor

that should fix it,unless you have a burnt valve. hope not

crank sensor seems to happen to alot of these cirrus

Doesnt the crank sensor use the flywheel for its signal maybe the sensor got damaged during the clutch job