QuestionI have a 4.3 V6 engine in a pickup and I am having problems. It starts, runs for approximately 3 seconds and shuts off. I have replaced the ignition control module, coil and a cap and rotor. Initially it did not have any spark so that is when I replaced all of the above. Now, it just starts and runs for 3 seconds or less and shuts off. There is no flashing lights for security system, etc. Do you have any suggestions of what else could be causing this problem. Thanks for your assistance!
AnswerYou have to determine if your problem is ELECTRICAL or FUEL related.
In most ELECTRICAL cases the fault lies with the CRANK SENSOR, BUT, Not always.
In most FUEL cases the fuel pum is the fault.
Here is HOW the fuel pump circuit works:
1. The fuel pump runs via the fuel pump relay for ONLY 2 seconds when you initially start the engine.
2. Once the engine stsrts, the fuel pump relay is BY-PASSED and is no longer controlling the fuel pump.
3. The fuel pump is provided battery voltage DIRECTLY from the vehicles computer. The realy is NO longer utilized once the engine starts.
Locate the fuel pump relay, usually under the hood and taped close to the relay on the electrical harness you will see a single wire with a plastic female end attached to it and this wire is connected to NOTHING as it is the FUEL PUMP TEST LEAD for diagnostic purposes ONLY.
Since this TEST LEAD is battery voltage (12 volts) you can probe it with a standard 12 volt test light.
Set up your test light in the TEST LEAD and watch it illuminate for only 2 (TWO) seconds and then go out as you turn ON the ignition switch. Do NOT start the engine.
Once this occurs, Leave the test light in place, Turn OFF the ignition and START the engine.
the test light should remain illuminated all the time that the engine is running.
Check this out and let me know.
autohelp
