I have a 2001 Ford F-150 4.6L V8 and recently for no apparent reason it won't start now unless it gets starter fluid, then it runs fine. Once it is turned off though, it won't start again even when warm unless it gets more starter fluid. My questions:

* If the engine is on, is it capable of sucking up fuel even if the pump isn't working? Since the truck runs fine and is drivable, I can't tell if I have a fuel pump problem or not. I figured I'd better check before I spend money on a gauge.

* Does this type of truck have a fuel sender unit? I lowered the spare tire and looked underneath and didn't see any device resembling the cracked/damaged units that I've seen in the YouTube videos. In fact the fuel tank is several feet ahead of the spare tire, under the passenger area.

* Do I have a fuel pump relay and an inertia switch, and where are they located? Googling brings up nothing useful. Can any of the switches/relays be reset?

* Where's the easiest place to use starter fluid? The only thing I can figure out is taking that strap off the giant intake hose and spraying inside. This is kind of awkward, and feels risky since I can only reach the clean side of the air filter here.

Thanks.

 

UPDATE: I felt around behind the right-side kick panel (slightly ahead of front door hinge, inside) and found what might be the inertia switch. I couldn't see it, but feeling around it I located the button. It didn't click and it felt like the button was already down, but my fingers may have fumbled across it earlier before I identified it. In any case the truck surprised me by starting successfully twice in a row with no problem. Will keep my fingers crossed but I'll check this thread anyway so I can learn more about the fuel system.

 

Using starter fluid isnt good for your engine! Get a fuel pressure guage and test the fuel pressure but first if you havens done it for awhile change your fuel filter!

 

The inertia switch cuts off the fuel line, so it wouldn't run fine after starting if that were the issue. Also, you may have depressed the button, but you could not have released the button without a small screwdriver or something. To release the switch you have to stick something into that slit on the side and then you'll here it click as it raises.

I would replace the fuel filter, and go from there...

 

I replaced the fuel filter. Still having the same problems. I am usually able to start the truck with lots of gas pedal pumping or using starter fluid, and once it catches it runs fine as if there's nothing wrong. Also it is stubborn to start when both hot and cold, so it's not the CHT sensor.

I've ruled out the inertia switch, since I unplugged it during the filter change to depressurize the line and it killed the engine in seconds. It's not popping open or anything.

Where do I go from here? I'm going to try to get a fuel pressure meter and put some premium gas in the tank in case I got bad gas or something (there's only a gallon in it right now).

 

Your laboring under misconceptions.
Pumping pedal does nothing. There is no pumping of gas when that is done.
The motor does not 'suck' gas from anywhere.
This is fuel 'injection' under high pressure electric pump action.
.
You need to trouble shoot by making some tests.
If you can get the motor to run by your method, measure the fuel pressure with a proper gauge attached to the test port on the fuel rail as a start.
Report what you see then go from there.
Good luck.

 

If you only have one gallon of gas in it, that is not enough. Put more in

 

OK, after changing the fuel filter yesterday, putting half a tank of premium gas in and today and driving it 30 miles, it is still hard to start. Here's the result of the fuel pressure test:

KEY TO ON... pressure rises to 5 psi and falls slightly. I can hear some kind of mechanical click in the engine compartment (a relay?) I'm not certain if I can hear the pump because of the noisy electronic chime.

CRANKING... pressure slowly rises about 2-3 psi per second while I crank. The engine starts up when the meter hits 15-25 psi.

RUNNING... pressure maintains a solid 30 psi.

I'm not sure what's normal or what this indicates exactly but I'm going to check the fuel pump fuses now. I've seen a few YouTube videos about a fuel sender module going out... is that a possible culprit? I don't even know if I have one of these, but if it has anything to do with the fuel gauge, the gauge is behaving normally.

 

Pulled out fuse #10 (Fuel Pump) and it looks perfect, swapped it out anyway, still difficult to start. Should I change out the fuel pump relay and would I be able to inspect it for damage or feel if it is hot? Or is that not likely to be an issue?

 

How does it idle now? Exact warm idle rpms.

Fuel pressure looks okay... on the low side but okay. When you turn the key to run, not start, do you hear the pump charge the lines? Try this just once, if you don't hear it or it's questionable, don't touch the key , leave it in the run position and hit the bottom of the tank with something. Don't cycle the key, just turn it right to run and listen.

That will just about rule out fuel unless you have some bad stuff in there.

If idle is bad or fluctuating, - rule out the EGR valve as being the culprit. Suck test it. What type plugs are in it?

 

Warm idle seems completely normal... 725-750 rpm. I even let it idle for 45 minutes while waiting in a school pickup line and the idle was perfectly normal, nice and smooth.

I listened while turning the key to "on" and I don't hear the fuel pump cycle on.

Here's where I'm confused: pulling the inertia switch wires out while the the engine on kills it in just two seconds. In fact, this procedure is what I've been doing to depressurize the fuel lines while diagnosing the issue. So how exactly is the truck maintaining 30 psi of fuel while it's running? Does this mean the pump is actually working? I don't understand this. Would this point to an issue with something like the fuel pump relay?

 

Then do what I said, so far it sounds like the pump.

 

But there's the issue of the inertia switch, which controls voltage to the fuel pump. Considering that I pull the inertia switch harness and it kills the engine, this tells me that the fuel pump is working. Also -something- is giving me a dependable 30 psi when the engine is on, which I guess is the fuel pump. But it's not behaving correctly at startup.

There is a writeup at this link on testing the fuel pump relay on a Ford. I am considering going ahead and working through this tomorrow, since I can't drop the tank here and do fuel pump work, and all I can do is wait until the mechanic opens on Monday.

 

None of that means anything, that's not the way the pump usually goes out. You skipped a major test in determining. It'll run, eventually, yours isn't starting right away, plus your a little less than average on pressure. That's exactly what happens when they begin to fail. Just put everything back together and rule out the pump first.

 

Your truck doesn't take premium unless you have modified the engine or computer. Premium fuel is HARDER to burn and is intended for higher compression/forced induction engines because it is less likely to pre-ignite from the heat generated by compressing the air/fuel mixture. All premium does for you is add carbon build up to your combustion chamber.

My bet is fuel pump. Your fuel pump will run for a few seconds when you turn the key on. It will stop running until the PCM grounds the fuel pump relay when it determines the engine is rotating. Try this... Turn key on, wait 5 seconds, turn key off, wait 10 seconds (I think) repeat that a few times and it should fully pressurize the rail and the engine should fire right up. If it does - replace the fuel pump.