For an engine to run, you need three things to happen inside the engine, compression,
fuel and ignition, without any one of these components the engine will not run.
If Your Engine Cranks but Does Not Start Follow this Troubleshooting
Guide
Most vehicles operate by the same principle; basic troubleshooting procedures
apply to most cars.
Scan for Trouble Codes
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Test Ignition System Video
This primary electrical signal is generated by the ECM which calculates spark
timing by using a variety of sensors including coolant temperature, mass air flow,
and oxygen sensors. To perform a basic ignition output test you must have a test
light and follow this ignition system output test video.
Distributor less Ignition System Configuration
Some ignition systems have a coil for each spark plug. This is called Direct
Ignition (DI) system; there are no plug wires in this system just individually controlled
ignition coils. The amount of coils or spark plugs depend on the number of cylinders
the engine is designed with, example: four cylinders, six cylinders etc. To perform
a basic ignition output test you must have a test light follow this ignition system
output test video and substitute the ignition coil for the plug wire (Note: leave
the coil trigger wires connected).
Coil Over Spark Plug
If the ignition system test is weak or non-existent test the car fuses, both
under hood power distribution center and the fuse panel under dash. This test is
performed with a test light tool. The test light should illuminate on both sides
of the fuse, if not the fuse has failed and needs to be replaced. If the fuses are
ok a manufacturer specific repair procedure is required and an online auto repair
manual is needed to continue. If the ignition system tests ok proceed to the next
step.
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Step 6: Test fuel system pressure, test for proper fuel pressure with a test gauge on the fuel rail or in line somewhere in the system, most throttle body injection cars (TBI) are between 13 psi and 17 psi. Most (DPI) direct port inject systems are between 40 psi and 55 psi. If good fuel pressure is present continue to next step. If no or little fuel pressure is present check the fuel pump fuse and fuel pump control relay located in the fuse panel, you can find this fuse and relay by checking your owner's manual, back of the fuse panel cover diagram, or an online auto repair manual, if the fuse or relay has failed replace it a new unit and re-test.
Poster Image
Checking Fuel Pressure Video
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(Note: some Ford cars have an inertia switch designed to cut off the fuel pump in the event of an accident. Sometimes this switch can accidentally be triggered causing the engine to not start. If the car is exposed to a random bump either in the road or by another car this switch can be triggered. To check for this condition locate the inertia switch, if the cut off switch has been active it will have a white or red indicator at the top of the switch. Push this indicator down to disarm the cut off switch, if the indicator does not move down it is not activated and is not the problem.)
Have a helper crank over the engine while you place your fingers over the relay, does the relay click under your fingers? If so the relay could be working, there is a chance the relay has burned contacts inside causing the problem but we will get back to that. Next, access the fuel pump power feed wire, there are a few ways to do this, first you need a wiring schematic to find the color wire needed for testing, the best way to do this is with an online auto repair manual. Once you have found the color wire it should be located in the wiring harness near the fuel tank were the pump is located. Ground the test light and probe (pierce the wire's outer coating with the test light point) the wire, have a helper crank the engine over. If the test light illuminates and you have no fuel pressure the fuel pump had failed and needs to be replaced. If the test light doesn't illuminate the fuel pump control relay has probably failed, replace it with a new unit and re-test, in most cases this relay is under thirty dollars. There is an outside chance the power feed to the relay has failed but it doesn't happen very often. If this is the case use an online auto repair manual to trace the power source to the relay.
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Step 7: Test fuel injector pulse and supply voltage output (test is used for most cars). This test will tell you if the computer system has operating voltage and injector trigger signal. Remove an electrical connector from a fuel injector (it doesn't matter which injector) probe both sides of the connector with a grounded test light (there are only two terminals). Have a helper turn the key to the "on" position without cranking the engine and observe the test light. The test light should illuminate one side of the connector only. Next, switch the test light lead to the positive side of the battery to test the system ground injector trigger, probe the side of the connector that did not light up, have a helper crank the engine over and observe the test light, it should blink on and off. If this test checks ok continue to next step. (Note: if no injector pulse is present try disconnecting the remainder of injectors and re-test, if a fuel injector is shorted it can shut down the injector driver causing no injector pulse. If injector pulse returns plug injectors electrical connectors in one at a time until the pulse fails and replace that injector)
If this test revealed that there was no pulse but system has power the ECM is not generating a fuel injector trigger. If there is no trigger to the fuel injector it will not allow fuel to enter into the engine. Some of the most popular reasons that can cause this condition include a shorted crankshaft angle sensor, shorted camshaft position sensor or shorted ECM/PCM. (When a system trouble code scan is performed it does not always catch a crankshaft angle sensor, camshaft position sensor failure). Tip: try disconnecting all non-essential sensors, example: oxygen sensor, coolant sensor, throttle position sensor, air intake temperature sensor, mass air flow or map sensor and EGR valve pressure differential sensor. Crank the engine over, if the injector pulse returns, one of the sensors is shorted causing the system to not operate. Plug the sensors in one at a time until the injector pulse fails then replace that sensor and reassemble.
(Note: Some Ford cars have an EGR valve pressure differential sensor that when the catalytic converter becomes slightly plugged will melt the sensor causing the system to shut down. Inspect sensor for melting at the electrical connector then repair or replace as needed and recheck.)
If the test reveals that the connector has no power on either side at any time the system power has been disrupted. Some of the most common reasons for this is condition are the main PCM fuse, main PCM power relay and main PCM power feed wire failure. (Some vehicle PCM feed wires are located near the battery and corrosion can stop the voltage feed). If all power sources check out the system ground needs to be checked, this is done by reversing the test light lead and installing it on the positive side of the battery. Now the test light will illuminate when grounded. Use the test light to check main system grounds to the PCM, most system ground wires are black but to be sure you will need an online auto repair manual. If repairs have recently been made a system ground lead could have been left off of the engine causing the system not to power up, so double check all engine wiring harness grounds.
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Step 8: If the engine has compression, ignition and fuel injector pulse and the engine still doesn't run it could have a plugged exhaust system. Disconnect the exhaust system before the catalytic converter and crank over, if the engine starts the car has a plugged converter or exhaust system. Disassemble the exhaust system to inspect to replace the exhaust component that has failed and reassemble to recheck.
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Welcome to FixYa.com engine does crank over no start, but tries to start check fuel psi--if your in a cold climate add some gas line anti freeze such as HEAT brand Thank you for using FixYa.com Regards, Lee Davidian
SOURCE: dodge caravan turns over wont start all lights work
possible bad fuel pump. check fuel pump relay under hood. drivers side fuse panel. swap fuel pump relay with another identical relay to rule out possible bad relay. listen for whining sound back by fuel tank. the fuel pump is in the fuel tank. Another option....you can also check the pressure in the fuel rail, but be careful not to squirt gas in your eyes or face.
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