2015 Ford E-350 5.4 flex fuel 198548.97 miles I've owned it since 30,000 miles and maintained it like I owned it lol. The check engine light came on and the codes were o2 sensors so I purchased new ford sensors and replaced them along with the monitor and the check engine light went off by itself so a couple months later the check engine light came on and the codes were rich bank 1 and 2 so I checked the air filter and it looks like new and has been replaced often so I cleaned the mass air sensor with brake cleaner and a cue tip found no dirt and after a day the check engine light went off. All this time it has run fine acceleration is good no problems. Now that the light is off for about a week now it doesn't want to start I tried a test that I saw were you turn the key on and off a few times before starting it and it seems to help and it does help but it doesn't seem to start like it used to. So why the starting issues and no check engine light?
I tried a test that I saw were you turn the key on and off a few times before starting it and it seems to help
sounds like the fuel pump might be getting weak .Put a gauge on it to measure fuel pressure and leakdown.
Would it run fine with a weak fuel pump? It's starting is the only symptoms of a problem
you have to start somewhere. A pressure test will also tell you if the injectors are leaking.
@imperator A diode in the fuse box had corrosion on one side. I continued to have starting issues even after replacing the fuel pump. There was nothing wrong with the fuel pump.
That's why I always tell people to test, measure, inspect etc before shooting parts at a problem. Thanks for following up.
According to the test turning the key on and off they mentioned a fuel pressure regulator. Is there such a thing on this motor?
I don't know, I've never worked on one of those vehicles. However that function is frequently incorporated into the pressure regulator. (That information should be in the shop manual for the vehicle.)
Do you need a special tool to check the fuel pressure?
A fuel pressure gauge.
Is there a tire type valve that I can press and fuel will spray out?
That depends on what your truck's fuel rail is equipped with for test purposes. Many vehicles do have a schrader valve of the type you're talking about but some have other types of fittings for testing fuel pressure.
What is the best way for me to test?
Test with a fuel pressure gauge after the engine has been turned off. There should be a specification in the shop manual for how much pressure is supposed to be retained for how long.
I found a stored code when I connected it to the fixd device that is a personal scan tool that you connect to your phone and it had a reset the check engine light option even though it wasn't on so I reset it and now it starts normal again. Thanks for your help 👍
Even though the check engine light went off by itself I found a stored code in the computer
what was the code?
the check engine light hasn't come back on so resetting it was the fix
That's not how it works, but
{black}:idontknow:
See what happens.
It was the same code that cleaning the maf sensor fixed. Running rich in both banks. The code cleared on the dash but the scanner still found it.
There is supposed to be residual static pressure in the fuel rail after you shut off the engine to facilitate gas flowing immediately to the injectors for quicker starts. This pressure is held by a check valve that may be built into the fuel pump or may be a separate part and if it fails you have to wait for the pump to pressurize the fuel system before the engine will start. Check that the fuel rail is holding pressure after the engine has been turned off for a while.
According to the test turning the key on and off they mentioned a fuel pressure regulator. Is there such a thing on this motor? Do you need a special tool to check the fuel pressure? Is there a tire type valve that I can press and fuel will spray out? I would expect issues running if injectors are leaking fuel. Lack of fuel pressure at start is looking like the most likely cause to me. What is the best way for me to test?
What is the best way for me to test?
with a fuel pressure tester.
Ask your local parts store if they have a loaner.
Even though the check engine light went off by itself I found a stored code in the computer when I connected it to a scan tool so I reset the code and haven't had a problem with starting and the check engine light hasn't come back on so resetting it was the fix. Thanks for the help.