I have a puzzling crank/no start issue that I'm trying to pin down, appreciate any suggestions. 2003 F150 Supercrew 4x4 5.4L 2 valve motor, just turned 73,000 miles. First noticed about 6 mos. ago, it would usually start on the 2nd try. It's been getting progressively worse and now stuck in the garage....got it to start a couple days ago after multiple attempts/cycling key on and off, etc. Here's what I've done:
Changed fuel filter
Swapped relays
Checked fuses
Verified inertia switch has not popped out
Pressure test at filter inlet
Pressure test at schrader valve on fuel rail

I'm wondering if it's an intermittent fuel pump issue. There is no fuel smell at the exhaust pipe after multiple start attempts, so that's why I suspect fuel pump. Also, after multiple attempts, if I spray start fluid in the air intake, it trys to start for a second. But here's where i'm puzzled....when I checked fuel pressure at the filter, after cycling the key several times, pressure would build up to about 65 psi. I borrowed a fuel pressure test kit and hooked up to the schrader valve on the fuel rail. With the fuel rail at 0 psi, turn the key on to prime the line and it will go to about 10 psi. After 1-3 more cycles fuel rail pressure will jump to about 33 psi, which seems normal? I listen carefully each time I cycle the key and notice the fuel pump doesn't run (prime) every time.....is that normal or should it try to prime the line every time you cycle the key on/off?

So wondering....dropping the tank to change the pump is a relatively big job, so I would like to pinpoint the pump as the culprit before I do that. Any experience with an intermittent pump like I'm suspecting? Even though I'm reading 33 psi in the fuel rail, could I be just below the threshold for the injectors to work? Any other suggestions for troubleshooting? Sure seems like a fuel delivery issue to me, unless I'm missing something....

 

Sounds like the fuel pump.

 

Have you considered a PATS issue?
. Does the Theft lamp light at key On then go out when cranking? If yes there is likely an engine or control issue.
If no and it flashes there is a PATS issue preventing starting as it is supposed to do.
If the steering wheel angle is changeable, try moving it up or down.
The wires may be broken from the movement. This can affect PATS operation.
When PATS is in fault the motor will not get fuel.
Don't launch. into any work until you are sure what the cause is.
Good luck.

 

Thanks for the quick reply. Any idea why it wouldn't start with what seems to be adequate pressure in the fuel rail?

 

Bluegrass.....Theft light comes on with key on, then goes out after a few seconds. No theft light or flashing theft during cranking.

 

That would seem to indicate no PATS issue.
Back to basics.
Is there ignition spark?
If not, check out the Crank sensor plug up.
If the computer does not get crank pulses, neither ignition nor fuel injection will work. This means no coil pulsing or fuel injector pulsing.
The fuel pump would still pressurize with key on because that function does not depend on the crank sensor.
When cranking, the crank sensor pulses result in restarting the fuel pump and times the ignition.
You have to find out what is not happening before any repair work is done.

 

Thanks. Is there an easy way to verify if I'm getting ignition spark? Besides checking crank sensor plug, is there a way to verify if crank sensor is working properly? Or do you just replace them....

Update: Since it almost starts with the starting fluid, isn't that saying spark is ok...and therefore crank sensor is probably ok?

 

With starter fluid, it should fire up immediately I would think. At least all my lawn tools will. Have you checked for codes? If so, what are they?

 

No, there is no CEL. CEL bulb check is ok. I've had the crank/no start for about 6 months now. Sometimes it would crank for 20 secs, turn key off, then start right up. Once it would start, it would run fine, no stumbling, no misfire. But now I've cranked it probably 20-25 times, enuf to where i had to recharge the battery.

 

Spark tester:



Noid lights (checks for fuel injector pulse):



You might find them at parts stores in the loaner tools.

Can I assume that you have tried starting it with the throttle cracked open, to rule out a bad IAC?

 

Yes, tried that and all the way to the floor.....no start.

 

All the way to the floor stops fuel during crank. Helps clear a flooded engine.

 

Just because there is no check engine light, that doesn't mean there are no codes that can be read. It's probably not your problem, but when mine was cranking always but only starting intermittently, it was caused by a bad PCM relay. From your posts, I suspect there are several issues contributing to your problem.

 

Yes, quite the puzzler. There are 4 relays in the box that are identical, and I've swapped them around. Pretty sure I have spark, because after several start attempts, if I spray a shot of starting fluid in the air inlet, it will start for a sec. So I think i'm chasing a fuel problem??

One other thing I should mention.....about a week ago, it would start after 2-3 attempts, cycle key a few times, prime fuel rail, etc.... I then changed the fuel filter. I have only got it to start once since then....and when it ran I drove around the block a few times, got up to about 60 mph, accelerated, etc....everything fine. So thinking the new filter may be an issue, I replaced it with a piece of straight tube i configured. Hasn't started since. Fuel rail seems to pressurized fine with the new filter installed or with the piece of straight tube. I'm stumped.....

 

Your injectors are probably not firing. Noid lights will prove or disprove that.