90 F250 4x4 with 5.8. Just happened yesterday. Will start for a brief second, then I can get it to idle fast for about 2-3 seconds, then it dies. I can smell unburned fuel when it does this, so I'm assuming that it's in the ignition. Any suggestions on where to start? I'm new to fuel injection. I'm going to see if I can pull codes tonight but was wondering what to check in the ignition system. What ususlly goes wrong there? Ignition module? magnetic pickup in the distributor?

Thanks for the help!

 

Check the fuel pressure to make sure it is not excessive.

Hook up a timing light and a remote start switch (or recruit a helper). Confirm that you are losing spark when the engine dies, rather than just applying the "nose test".

If spark is being lost, disconnect the SPOUT jumper (small gray jumper near the TFI module). See if that clears up the problem -- this removes the ability for the computer to control the spark. The ignition system is capable of running without help from the computer.

The TFI module gets a "hot in run" and a separate "hot in start" wire. If there is a problem with the harness, it may not be getting the "hot in run", and only generates spark while it is cranking -- although I don't think this would leave it running for two seconds.

Two seconds sounds suspiciously like the fuel pump run window, or the transition from "start" to "run". The computer kills the fuel pump if it does not see the PIP signal for a period of two seconds. It will also stop injecting fuel with no PIP from the TFI. But it may inject a fixed amount of fuel, and run the pump, as long as it can sense that the engine is cranking, and for two seconds thereafter.

Try jumpering the "FP" wire in the diagnostic test connector to ground. This should force the fuel pump to run as long as the key is in run or start. See if this changes things.

The TFI module fails somewhat more than the pickup coil, but it is often wise to replace both if the ignition is flaky. Saves the cost of a tow.

Check all of your ground wires. Battery cable, Frame, engine, PCM at firewall, chassis grounds on radiator support.

 

Fefarms, Thanks for the info! Great post! I will try all of what you suggested. Any other comments / ideas?

 

Get a cheap ($4.00) test light. Hook the alligator clip to ground. Probe the + side of the coil primary during crank and the few seconds the engine runs (again, you need a remote start switch or a helper). The light should stay lit the whole time. If it ever goes dark, suspect your ignition switch or main battery wiring.

Repeat with the - side of the coil primary. The light should be lit with the key on, it should flash when the engine is cranking, and keep flashing as the engine runs. If it stops flashing and stays lit right as the engine begins to die, suspect the TFI. If it stops flashing and goes black as the engine begins to die, suspect the ignition coil

Repeat with the FP wire. The light should go dark for two seconds as the key is first turned on. It should then be lit. As you crank the engine, the light should go off, and stay off as the engine is running. If the light goes on before the engine starts to quit, then there are issues with the fuel pump control.

 

Finally worked on it this weekend. I bought a code reader, but all that told me was some emissions control equipment was out of range - EGR Valve and Coolant Temp Sensor. Those tested fine. Then tested the fuel system - no problem. Then tested the electrical system. Coil tested good. Ignition Switch and battery - good. I then hooked the test light to the negative side of the coil and observed while cranking and starting. Intermittent light while cranking - solid light while attempting to run. Traced this to either the PIP pickup coil in the distributor or the Ignition Control Module mounted on the outside of the distributor. I replaced the whole distributor with both of the components, so I'll never really know which one it was, although I suspect the PIP Sensor. I just didn't have time to pull the distributor completely apart to get to it. Runs great now. Hopefully this will help someone with the same problem.