Recently my 2001 F150 4x4 5.4 truck has been misbehaving by being difficult to start at random times. The engine will turn over with however will not fire. After some time, I am able to get it to fire. When this happens the truck start normally for the rest of the day and maybe several days. Around the same time, error codes for a variety of sensors would occur. This problem was traced to a broken PCM connection. When this problem does materialize, no error codes are generated. After some time in repair shop, a probable cause could not be found. If anyone provide some direction to look, I appreciate any comments.
Which is it, was the problem traced to a broken connection or could a cause not be found?
Let me clarify. The problem being addressed is the starting issue. Secondarily there was problem with the PCM which was resolved by replacement.
Thank you for the suggestion.
Thanks for the clarification.
How’s it run immediately after the symptom occurs? If it runs rough, you might have a bad temp sensor. Since the ECU has nothing to compare this to, it won’t throw a code but the engine will run rough until it warms up.
One thing you can try is putting the key to ON a few times for about four seconds each before turning it to START. It’s possible that the fuel lines are losing pressure and the fuel is draining down when the vehicle is parked overnight. If that’s the case, putting it to ON a few times in the morning should refill and pressurize the fuel lines.
I had a vehicle back in the '70s that I used to have to do this with. Let us know how you make out.
I like mountainbike’s suggestion
Without even hooking up a fuel pressure gauge, you’d know you have a fuel problem
Other posters here who have had this problem on their own vehicles (not necessarily Ford trucks) later discovered the problem was the fuel pump check valve was on the fritz, allowing the fuel system to depressurize after the engine is turned off. The gas flows back into the tank instead of staying inside the fuel rail ready to go for the next start.
I ran a quick test today by placing the ignition in the “RUN” position for about 3 minutes, after the vehicle has been unused for about a week. The result it started as it should. I was planning to rework this test shorter periods to see if this observation holds. Since it can require several days in between to get it in a no start condition, not sure when the next will occur. It is an interesting comment regarding the check valve, sounds like a good possibility.