QuestionQUESTION: What controls the opening and closing of injectors, there is pressure on the rail, but car doesnt start.
2001 chevy blazer s-10 4.3L engine.
simplecpi
ANSWER: Hey,
There may be fuel pressure, but it it adequate? That system needs minimum 55psi to start with the CPI injectors.
The ECM or PCM (computer) receives input from various engine sensors like Mass Air Flow, Throttle position, coolant temp and engine rpm. With this data a base pulse width calculation is developed and the solenoids in the CPI unit are pulse modulated to allow fuel volume to the poppet style injector tubes. Many of these inputs can be missing or incorrect but some of them are required for a fuel ratio that is close to stoichiometric.
To answer the question the PCM controls the injectors but the PCM needs many inputs, power, ground and logic to do this. If you definitely have 55psi (not just checking the schreader for a squirt) then a scan tool will be needed to see if the computer is attempting to generate a pulse width for the injectors. At 53psi that engine will not start. You need to check it with a pressure gauge.
Wayne
---------- FOLLOW-UP ----------
QUESTION: what will keep it from generation 55psi, or proper pressure for opening and closing the injectors.
ANSWER: Defective pump or regulator or plugged filter.
w
---------- FOLLOW-UP ----------
QUESTION: does the crank sensor has anything to do with the fuel injectors.
AnswerHey,
The crank sensor is the most important sensor responsible for fuel calculation. If the computer does not receive an RPM reference it will think the engine is not revolving and not inject fuel. The crank sensor can be tested with a DVOM or graphing meter. If a scan tool is hooked up to the PCM there will be no RPM data when cranking if it is defective.
Wayne
