Yr 2000 F-150 with V6 . only 68K miles. 3 weeks ago went into
fast food for lunch and then truck would not start. The starter would spin
it over real well and plenty of gas etc etc. I came back the next day
with a tow truck to take it to the dealer and it cranked and ran perfectly
for 3 weeks till yesterday. Same thing. Will not start in parking lot
of grocery store. I only have one key and someone suggested that
it could be the chip in the key or the theft system acting up. I only
have one key from when I bought the truck 7 years ago used.

Someone else said when the anti theft system is screwing up, the motor
will be totally dead and starter will not work. Can anyone confirm?

This time I am again planning to tow to the dealer and I fear a huge bill
for something that is actually very tiny at fault since the truck runs
perfectly well and then mysteriously will not start.

This is the 2nd time in 3 weeks I have been stranded. I pulled all the
fuses and reinserted. I checked all spark wires and they are in good shape
and tight. What could it be that all of a sudden causes the engine to not
start up and run intermittently ?

I sure hate to have to pay dealer rates for diagnosis and repair it it
is something I can do myself and I am pretty capable. I replaced in the
last year waterpump, power steering pump, ball joints and alternator.

So what is not getting..... fuel or spark ? The only two things we need
for to run ... right ?

 

You need knowledge first to recognize when you see a fault.
A. The anti theft system will prevent starting if there is an issue or attempted action other than by normal key use.
It usually inhibits fuel.
B. A loss of power by the PCM due to relay seating, fault, blown fuse etc.
C. Faulty fuel pump or it's circuit.
You have to investigate these areas the same as a dealer would normally do..
It has to be done when the problem is present or you get nothing found by the dealer and it will happen again.
.
Start by looking at the Theft light for blinking. If yes, your issue is not the engine control system even though it's fuel is inhibited.
If ok, next check for fuel pressure with a gage on the test port while cranking.
If no pressure, does the pump run a few seconds at key on? If no, several possibilities are possible. PCM is not powered up, the crank sensor plug is not seated firmly etc.
You see now why you need to know some of these operational sequences.
Good luck.

 

This might not be your issue, but when I first got my truck, I would jump in and hit the key as fast as I could. The theft system acted up on me several times over a few months. I read somewhere that it was possible I was hitting the key before the computer got a signal from the key. It would eventually go away on its own each time. After reading that, I started turning my key on, and letting the fuel pump do it's thing, then start. It hasn't done it at all in the four years since. Might not be your issue, and might even be a fluke on my end. But I'll tell ya still, it sounded right, and seems to have worked.

Outside of that, Bluegrass is right about the procedure.

 

Yes absolutely would love to know the sequence of operation and diagnosis.
I dont know where the fuel test port is but would love to hook up a fuel pressure gage and leave attached permanently just like in the old days.

update: This morn I went to where the truck is and put my ear against the gas tank and I could never hear the fuel pump running when someone would turn the key to ON. I sprayed starting fluid into the air filter and it cranked and I drove it 25 miles home. Are we certain that the fuel pump is supposed to buzz/run when the key is on ? It had to have been running
during the drive back home. Then after getting home, it cranked up a few times and after 30 minutes would not crank again. I already replaced
the fuel pump relay.

Also.... Where is the Theft light that might be blinking ? Please explain again whether it should be blinking or not be blinking and what that means ?

Did I correctly understand that the theft system inhibits the motor from
starting by cutting off power to the fuel pump ?

 

Follow closely;
at key on, the pump should run only a couple seconds then go off.
This is normal until the motor is cranked then it turns on full time.
You have to sure your there to hear it for that short interval.
.
Fuel pressure testing;
the port is along side the fuel regulator and has a standard valve end like a tire stem and may have cover on it. It is located on driver side over cylinder 7 area.
.
Connect gage hose for a seal then turn key to on several times for the pump to run each time and build pressure to about 35 psi.
Be awhere that if the pump is intermittent, you have to recognize that fact.
I would not leave a gage attached to the fuel rail any longer than needed, for safety sake and fire..
.
The Theft lamp looks at you on the top portion of the dash panel display.
It says THEFT in RED.
If it (fast) flashes when you crank the motor there likely is an issue with the system that may be causing a lack of fuel, as it is supposed to do.
Your getting close to the problem now, just pay attention to detail.
Good luck.

 

Re: The usage of the word "crank", when discussing an automobile engine, means the starter is operating and the engine is rotating. If the engine "cranks but does not fire", that means something totally different than a "won't crank" symptom. The terms mean very different things.

 

Thanks for all the helpful advice but I fear we may be talking about slightly
different models of trucks and the behavior may be different. For instance,
I have the 4.2 V6 yr 2000 F-150 2wheel drive. ( I dont have a cylinder #7)

I have never seen a theft light on the dashboard or a blinking red light.
My ignition key is computer chipped but I do not have remote entry and
fancy stuff etc. Manual locks and roll up windows etc.

I literally crawed under the truck and held my ear flat against the bottom
of the single tank that is ahead of the rear axle. I hollered to my friend
numerous times to turn the key to on position then to off. Then yell to
start and the starter would turn the motor over while my ear was pressed
to the tank. Never a fuel pump sound. Then I disassembled the airfilter
assembly which allowed me to spray in starter fluid and it started immediately.
We let it run for five minutes then I drove it all the way home.
No that I am home I will actually use a medical stethescope placed right
on the main tank and listen for fuel pump noises with someone else
turning the key on and off.

I apologze for the poor word choices. Yes I see the confusion and the need for distinguishing between the starter turning the motor over and the engine actually starting up and running. "Cranking" as a term can be misleading. Sorry.

So I am still wondering if the theft system, chipped key or the key transducer that reads the key could be causing my problems which
are leaning more toward inadequate fuel flow or mistakenly inhibited fuel flow.

What can we infer from the fact that I never hear the fuel pump and yet
I drove the truck 25 miles after starting with starter fluid ?
...... again yr 2000 4.2 V6 2wd basic truck ?
If I should get the truck running again, I wonder if there would be too
much noise for me to again put my ear up against the bottom of the tank
or with the use of the medical stethescope ?


I swapped out the fuel pump relay so far and nothing else.
I am confident I could lower the tank and install a new fuel pump
if need be.

What is next in the logical sequence ? Whenever I locate and inspect
the fuel line test port I fully intend to buy a fuel pressure guage if not more
than $75 dollars.

 

We can infer your truck gets CRAZY good gas mileage 25 miles on a shot of starter fluid beats a Prius!

On a more serious note, I would jump right to a new fuel pump (assuming you tested it for power at the fuel plump plug itself). It's acting like an intermitent fuel pump failure if you ask me. Started on spray, the vibration of the engine starting kicked off the fuel pump and once the pump starts rolling...it's usually good to go even if it can't restart on it's own.

 

OK. Today my project is to replace the fuel pump and I hope to be
able to find the plug first to test for power as suggested previously.

I still hope my theft system is not causing the inhibition of power getting
to the pump.

 

If the PATS system is triggered (fast-flashing THEFT light during a starter attempt), the system disables the fuel injectors.

I would conclude the fuel delivery system is intermittent and that the pump actually started up when the engine fired on the ether.