2003 F150 4.6L V8

This is a friend of mines truck. Months ago on a 10 hour road trip, early in the trip home the truck all of a sudden shut down as if you turned the key off. The truck runs extrememly smooth, no warning ......... all of a sudden...... boom it shuts down. When this happens you have to wait a few minutes or longer before it will start.... engine/starter turns over fine.... it just wont start (as if it's not getting gas). After finally starting, he drove the remaining 8-9 hours without issue and it has been fine since then until this weekend.

This past weekend while driving around town it did it a few more times. He has to wait anywhere from 5-10 minutes to over an hour to start. Again, the truck runs like a top...... very smooth....... and all of a sudden it's as if someone turned the key off. Everything just shuts down.

There are no idiot lights or warnings lights noted.

I have been reading/searching looking for answers. Here are solutions I've found to similar situations:
-- fuel filter
-- fuel pump
-- PCM
-- grounds
-- fuel pump relay

I changed the fuel filter for him. Dirty, but not to unusual. We then started the truck and it ran fine. After idling for about 10 minutes he turned the key off. Then........ it would not start...... turned over fine...... just would not start (again as if it's not getting fuel).

While changing the fuel filter we hooked up a fuel pressure test kit on the fuel rail. We started measuring pressure before starting while turning the key and pressured up to about 28 lbs before starting. Pressure was fine after starting and ran steady at 32-34lbs. We still had pressure gauge hooked up when truck was turned off and attempting to restart. Fuel pressure remained fine at 32-34 lbs.

He took it into dealership yesterday hoping to get a fast solution as he needs to use truck daily. Ford kept it all day and at 5pm they told him they checked several things and do not have a clue. (I'm assuming they pulled diagnostic codes but they did not mention .... he is going to specifically ask this AM when he pics it up.)

Anyway ......... at this point we are clueless.

 

I will update with any info from dealship as soon as he pics it up this AM.

 

I would want to see a scan tool on the vehicle "recording" when the event happens or it fails to start. It could be a loss of crank signal. With a o-scope hooked to the

crank you would find that pretty easily. An engine requires 3 things to run, a spark, compression, & fuel. If it has fuel psi when it won't start then it doesn't have spark.

You know it has compression if it will eventually run and does so smoothly. I would focus on why it is loosing spark. A crank sensor is $30ish, and easy to change, that is

my guess but I would scope it before I throw parts at it if the problem can be quickly replicated.

 

UPDATE:

Ford kept the truck this AM to check injectors. Bottom line: $146 and Ford dealership does not have a clue. No codes found except a battery disconnect (my buddy did that himself and dealer caught him ). Dealer could had it a day and 1/2 and could not replicate problem. Everything they checked was OK.



joshmac4.6: I agree with your logic.... if the crank sensor was the problem ..... wouldn't this throw a code???

That's what baffles me. No codes.

One problem is that the problem cannot be quickly replicated. There appears to be no schedule or warning ........ it appears to happen randomly.

Thanks for the input. This may take a while to troubleshoot. Still baffled by the fact that there were no codes.


QUESTION: What situation would cause the truck to totally shut down as if you turned the key off..... and...... would not throw a code???
And then, cause the truck to turn over but not crank???

Or, what would cause the engine system to not throw sparks but not throw a code ???

 

Not necessarily - something could be keeping the injectors from firing. You can check this with a noid light.

 

Nope! Check the connector. Might be a flaky fuel relay. Swap it with another like it, - or see if it's warm by touching it. Warm = Bad.

 

Lots of time injectors not firing will cause a "deadhead" pressure reading. The fuel pressure would be abnormally high if the injectors were not firing. It is possible that the injectors are not getting fire but they would also use a crank reference like spark. The fact that it doesn't have codes does not surprise me. Ford diagnostics have always let me down. I had misfires for months. They were very sporadic and sometimes extremely severe. The misfire monitor was clean, recordings showed nothing, and an o scope of sensors never brought anything to life. I tried new coils, wires, plugs, clean maf tb and iac, swap fuel and octane with no luck. The truck would miss for up to 10 secs but never set a code. I was in Ford FACT at the time and had multiple ford master techs ride along but none could offer an explanation.

I don't like to throw parts at one but if the problem is so hard to replicate based on the cost of a crank sensor I would try one.

 

Yea, the rail shuts down after 4 consecutive seconds of cranking, - protects the cats.

 

The first step is getting an at the rail fuel pressure read when the no start occurs. My guess is you got an intermittent failing pump

 

UPDATE #2:

Thanks for all the comments!!!

No new episodes to report. He has driven the truck a few hours around town since he picked it up from Ford. No new problem episodes and all is good except..... he knows its going to happen again.

All of the ideas about scan tools and fuel rail pressure during an event are great. Except ........ no one knows when the next event will be. It may be next week, next month, next year...... who knows.

joshmac4.6: You hit the nail on the head. I don't like to throw money at parts but if replacing $40-50 in parts (fuel filter, fuel filter relay, camshaft position sensor, etc.) have a change to eliminate the issue.... why not. Especially since it appears so difficult to replicate the problem.

I'll try and report back with any finds/changes/updates ....... thanks again for all the comments!!

 

im betting its a fuel pump.. Father in law had a dodge that did the same thing, it would run for months fine then all of a sudden for a few days it would just die. One time i was with him and it did it. i crawled up under the fuel tank and beat it a few times with a hammer and it fired right up.. Changed fuel pump and never did it again

 

My money is on crank sensor too. Been quite common of problem to people I know. I believe they are cheap and easy to exchange, looks like $20 at most. Just keep in mind.

 

Running round with low fuel will kill a fuel pump. It needs to be immersed in fuel to keep it cool. Keep the fuel pressure gauge handy and the next time it dies hook up the gauge and check the pressure. When it dies and finally restarts do the gauges sweep? That is a sign of a power failure. Check the battery terminals and all the leads coming from the battery to their destination for proper and clean connections.