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About a year ago my 2001 F-150 5.4 liter truck suddenly would not start, there were no warning signs, it was running fine when I stopped at Walmart on the way home from work and it never started again. After towing it home I diagnosed that it was a fuel issue and ended up replacing the fuel pump. I replaced the fuel pump and it ran great for about 6 months.

6 months after replacing the fuel pump it would randomly have trouble starting on hot days, if I kept trying it would eventually start (for some reason removing the gas cap seemed to help). Someone told me this could be an issue with the battery so I replaced that, but the difficulty starting continued and then started happening in all temperatures. About that same time it started to run rough, like it was chugging and starving for fuel until it eventually it just did not start any more.

I suspected a fuel problem again so I checked if it would start up with starting fluid and it did (for a few seconds then would die). I assumed either the new fuel pump had again gone bad, or that the tank was not clean and debris were clogging the pump (I did not clean the tank with the previous replacement). Today I changed the fuel pump and cleaned the tank thoroughly, but when I got everything back together it still will not start.

It still starts and dies with starting fluid, but will not take hold of the gas. I also verified that the pump is in fact pumping by draining the fuel at the fuel filter till there was none in the line, reconnect and attempt to start, then check for fuel in the line and there was plenty... Not sure what my next step might be. Any help would be greatly appreciated.

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  • Possible faulty new fuel pump, putting a fuel pressure gauge on the fuel rail would verify this.
    – Moab
    Sep 30, 2019 at 20:35

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Because the motor fires and runs briefly using starting fluid, the starting and ignition systems can be presumed to be OK.

The truck's problem is fuel flow. You've shown there's fuel at the fuel filter, but you need to go farther and check beyond the fuel filter. Somewhere between the fuel filter and the cylinders themselves fuel isn't flowing.

I don't know this motor, and don't know if it has a carburetor (or carburetors), or fuel injection. If the former, a fuel line or carburetor jets could be clogged or plugged. If the latter, the injectors might not be operating because of an electrical fault, or physically plugged and inoperative due to gunk in the fuel system.

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  • I might try the injectors next, but what are the chances that is really it? Wouldn't all of them have to be gummed for it not to start at all? Seems like quite a coincidence to me. I did do a seafoam treatment on it a couple of weeks before it died for good to 'clean out the injectors' and the guy told me he saw more smoke coming off of it than any other vehicle he had ever done... any chance that loosened up some gunk elsewhere and actually made things worse?
    – krayzk
    Sep 30, 2019 at 1:01
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    Sure, anything's possible. Take an injector out, lay it on the motor to make sure it's electrically connected, and crank the motor. Does atomized fuel spray out? If all the injectors are inoperative, I think an electrical fault in the FI (so no energizing current is supplied to the injectors) is more likely than all the injectors being physically clogged. But you'll have the same no-fuel symptoms if fuel isn't being delivered to the injectors' fuel rail because there's still some impediment in the fuel line before the fuel rail.
    – DavidRecallsMonica
    Sep 30, 2019 at 1:05
  • For some reason electrical fault strikes me as the more likely culprit, when it was intermittently starting it (seemed) to help if I put the battery on some kind of charger or jump starter (hence the battery replacement). If there is a lot of impedance to the current getting to the fuel injectors it might explain why additional current helped things along. The currents path might have finally degraded to the point where even those things would no longer give it enough juice.
    – krayzk
    Oct 2, 2019 at 15:51
  • I agree. In your truck, a fuel flow problem can be mechanical (gunk or blockages in the lines or injectors) or electrical (preventing current from reaching the injectors as it should).
    – DavidRecallsMonica
    Oct 2, 2019 at 16:21

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