Medium and Heavy Trucks
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Hi David, My name is***** will be glad to help. Is the malfunction engine light on?
What codes are you getting?
I see you replaces the speed sensors already. Check the harness and connector pins to be sure the ECM is actually getting the speed signal. You should have 5 V to the sensor and the ECM reads the return voltage
Check the fuel lines between the tank and pump for leaks or restrictions sucking air. will it fire on silicone spray or ether?
Install a clear hose or site glass to check for air bubbles. If low fuel supply pressure you could have a faulty fuel transfer pump
Low coolant will shut it down but would throw a code usually for shutdown