I have a 2001 2WD Crew Cab F150 Lariat with the 5.4 Triton that won’t start, I have replaced the fuel pump and filter, when i turn the key on the pump runs for a second then quits, I understand that’s normal, when you try to start it I still have power to the pump but the pump won’t run, I have 12 volts to the pump and 6 volts to the sending unit, if I jump the fuel pump relay the pump runs but the truck still won’t start. I can spray starter fluid into the throttle body and the truck will run for a second or two. I have ran out of ideas to try. I have thought about replacing the fuel pressure regulator but not sure that is the problem. Any ideas would be appreciated. Thanks.
So it cranks ok, robustly, but won’t catch and run? But it will catch and run briefly w/starter fluid sprayed into the air intake? hmm … definitely sounds like fuel isn’t getting injected. And the pump has 12 volts to it when you jump it, but it still won’t start? Must be either the fuel pressure is wrong, or the injectors aren’t being pulsed. Suggest you test for each of those possibilites.
Heres another idea: Does your fuel pressure regulator have a vacuum hose attached to it? If so remove that hose for a look-see. If there’s any gasoline inside that hose, the fpr is shot and must be replaced.
The problem might be with the Crankshaft Position Sensor.
When the ignition is first turned on, the computer grounds the driver for the fuel pump relay for a second or two to prime the fuel system.
Then when you crank the engine, the computer looks for the signal from the crank sensor. If the computer doesn’t see a signal from the crank sensor, the computer thinks the engine isn’t rotating. So it see’s no reason to run the fuel pump.
Tester
1 Like
If the crank position sensor wasn’t working there would be no sparks, so it wouldn’t run briefly with starter fluid in the air intake. Also the OP says they jumped the pump for test purpose and know the pump is getting a full 12 volts, but it still won’t start.
I have pulled the vacuum line off of the FPR and no fuel came out of the line.
I think the next step is to use a noid light (or equivalent ) to see if the injectors are getting pulsed That’s easier than measuring the fuel pressure. Was there anything unusual that happened between the time when the truck started ok, and when it didn’t start at all? You sure you have gasoline in the tank right?
Can you explain how to text to see if the injectors are getting pulsed.
Nothing unusual besides it sit for about a month and yes it has over half a tank.
If it worked ok, then unused for a month, I’d probably do a quick test to make sure there is plentiful amount of gas flowing into the fuel rail when the pump is powered up. Gasoline safety procedures rule of course.
Tester
Ok I’ll check that tomorrow and try the noid lights to see if the injectors are getting power. Will I still be able to see if the injectors are getting power even if the vehicle won’t start?
Yes. the injectors should be pulsed repeatedly with a brief time interval of current, which the noid light will show by lighting up as shown in the u tube vdo. If they aren’t being pulsed the engine will not run no matter what else you do.
There’s a bit of a mystery why the pump runs when you turn the key to on, and when you jump it, but doesn’t run during cranking, even though you measure it is fully powered during cranking. My guess it is running (or at least making a noise like it is running) during cranking but you can’t hear it b/c of the other engine noise.
Ok thanks guys, I will try those things tomorrow and let you know what results I get. I’m going just take a guess here and say that if the injectors are not getting any power then it’s a bad ECU?
That wouldn’t be my first guess. There are quite a few more tests you need to do before consider the ecu as a suspect. You definitely don’t want to replace it until those tests are done, b/c you may end up with a much worse problem than what seems to be the relatively minor one you now have.
No!
If the crank sensor is bad, the computer will not operate the fuel system (injectors), or the ignition system.
Tester
1 Like
Ok I’ll do those two tests and let you know what I find. Thanks again.
Tester above may be suggesting the crank position sensor is intermittent, which could possibly explain the unusual observation (for a failed crank sensor) of still running briefly when starter fluid is used. Checking for sparks at a spare spark plug tip during cranking might be a worthwhile test.
Ok thanks gives me s few more things to try.