The location of the fuel pump relay on my F250 super duty, 5.4
Country: United StatesMake: FordModel: F250 Super DutyYear: 2000Engine: 5.4
throwing codes PO 171 and 174. "System Adaptive fuel to lean". Replaced fuel filter and am getting ready to replace Idle control motor however I'm told a bad MAF sensor will prevent starting. The above codes are the only ones being sent. Ralph
Hello and thanks for using Just Answer.I will try my best to help you with your question.
The lean codes are most likely caused by a vacuum leak. Inspect the PCV hoses from the passenger side valve cover to the back of the engine. Make sure the rubber elbows are not soft and sticky or collapsed together. Oil in the system causes the hoses to fail and break down causing lean codes like yours. Check and repair any PCV hoses and then clear the codes.
The truck won't even hit now as if there is no fuel. Yesterday it started and ran until the daughter brought it home. I went to start it again and it hit, ran a few seconds and died. Now it just cranks as if there is no fuel. Will a bad MAF sensor prevent starting or the fuel pump relay finally dying preventing the fuel pump from operating?
The MAF will not cause a no start and no fuel pressure.
There is a test port located on the fuel rails for the fuel injectors. The test port is on the passenger side of the engine on the intake manifold back behind the heater hoses. Push the needle valve down and see if you get a BIG spray of fuel. If not, you more than likely have a failed fuel pump.
A fuel pump relay will, however, prevent the fuel pump from operating is that not correct?
Yes, and so will the inertia switch. The inertia switch is located under the dash on the passenger side behind the plastic panel on the floor. See if you get power on both sides of the switch at the wire connector. If you do, try to start the truck. If it will not start and still no fuel pressure, the fuel pump has failed.
I have "NO" power at the inertia switch. Relay? Fuse?
No power at the inertia switch means either a fuse of the relay.
The fuse is #19 a 20 amp fuse under the hood in the engine bay fuse box. The relay is located under the dash next to the steering column on the passenger side of the steering column.
I bought the relay but for the life of me see it no where under the dash to the right of the steering column
Do you have power on the fuse #19 under the hood with the key turned on?
First let me appologize for not getting back to you as I was sent out in the field 10 days ago. I need to let you know my fuel pump relay is "not" under the dash but under the hood in the same box as the #19 20 amp fuse. I only have one more question and I will close this out for you. In the front of said fuse\relay box in the engine compartment are two items that look like fuses however are solid black and have opposing blades. They also have a diode symbol on top of them. One of them will cause the fuel pump relay to cycle as you take it out and put it back in. What is the purpose of these. TY.
Sorry about that, my diagram from the factory shop manual shows it under the dash to the right of the steering column.
The black fuse like plugs are Diodes. They absorb voltage spikes in the circuits.
Below are the wiring diagrams for both diodes.
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