7.4 mpi won't start
 

I have a 7.4mpi that won't start it turns over and I have good spark and fuel pressure and still nothing if I spray a little starter fluid in it it will start and run fine does anyone know what would cause this ?

Try tapping on each fuel injector with a screw driver. Sounds crazy but the pintle in fuel injector can get stuck. Had it happen to me this passed spring.

With the ignition switch in the start position the ECM will turn on the fuel pump relay. The electric
fuel pump runs and pressurizes the fuel in the fuel rail. The ECM then checks the Engine
Coolant Temperature Sensor (ECT) and Throttle Position Sensor (TP) to determine the proper
air/fuel ratio for starting. The ECM controls the fuel delivered to the engine by changing the
pulse width of the injectors.



ECT Sensor
Temperature - to - Resistance Values
(Approximate)
°F ---- OHMS
210 = 185
160 =450
100 = 1,800
70 = 3,400
40 = 7,500
20 =13,500

The Engine Coolant Temperature Sensor (ECT) is located on the port side of the thermostat
housing. It sends a signal to the ECM letting it know if the engine is warm or cold. The voltage
is high when the engine is cold and low when the engine is warm. The ECT is a two wire sensor
using a 5 volt signal from the ECM. A typical reading is 160 deg. and if the sensor fails a 14,
or 15 failure code is stored inside the ECM.

The Throttle Position Sensor (TP) is mounted on the underside of the throttle body assembly.
As the throttle is opened the TP sends out a changing voltage signal to the ECM so that it can
adjust the fuel delivery. The TP also signals the ECM when the throttle is opened rapidly so
it can add extra fuel for acceleration. The TP is a 3 wire sensor using a 5 volt signal from the
ECM. Signal voltage will vary from .7 volts at idle to 5 volts at wide open throttle (WOT). If the
TP fails the ECM will hold a 21, or 22 failure code.

This might be a good place to start looking