Mechanics

WON'T RESTART UNTIL 30 MINUTE WAIT

2003 Ford F-150 • 65 miles

2003 Ford F150 FX4 Supercab, 4.6L V-8, 65,000 miles. Coils replaced at 63,000 miles.

Took it on a short ride of 2-3 miles, shut it off for 2-3 minutes, and it would not restart. Gas tank ¼ full. It would ‘try’ to catch but couldn’t seem to get above a rough stumble. Tried it off and on for 10 minutes, then called AAA. After waiting 20-30 minutes for AAA I decided to try it one last time. Started right up like nothing was wrong. “Check engine” light was OFF. Read code at home PO460 ‘fuel level sensor A circuit malfunction’.

Drove the truck for a couple of weeks, mostly around town. Never filled tank above ½. Yesterday took a short drive of 4-5 miles. It did the same thing. Would not restart, was ‘trying’ to but wouldn’t fully catch. Tried multiple times, then decided to try the ‘wait and let it heal’ thing. After 25 minutes it started right up. NO ‘Check engine’ light. Same code PO460. Gas tank was between ¼ and empty. This time I filled the tank to the top. It took 21-gallons in the 25-gallon tank.

The gas gauge appears to be working correctly. When the truck IS running it runs perfectly.
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Forqueue
April 26, 2013.




All "crank, no start" conditions are approached in the same way. Every engine requires certain functions to be able to run. Some of these functions rely on specific components to work and some components are part of more than one function so it is important to see the whole picture to be able to conclude anything about what may have failed. Also, these functions can ONLY be tested during the failure. Any other time and they will simply test good because the problem isn't present at the moment.
If you approach this in any other way, you are merely guessing and that only serves to replace unnecessary parts and wastes money.

Every engine requires spark, fuel and compression to run. That's what we have to look for.

These are the basics that need to be tested and will give us the info required to isolate a cause.

1) Test for spark at the plug end of the wire using a spark tester. If none found, check for power supply on the + terminal of the coil with the key on.

2) Test for injector pulse using a small bulb called a noid light. If none found, check for power supply at one side of the injector with the key on.

3) Use a fuel pressure gauge to test for correct fuel pressure, also noticing if the pressure holds when key is shut off.

Once you have determined which of these functions has dropped out,
you will know which system is having the problem.

Wrenchtech
Apr 26, 2013.


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