High Milage Fuel Filter replacement

[Vinson581]

I finally have started on my explorer (long travel build) last night, and while i was under it i noticed the rusted nasty looking fuel filter which prolly had 175k miles of dirtyness( i got the explorer @150k for the price of free)I decided to datalog the truck using sct's advantage III + livelink, w/ an xcal i had laying around, well lets just say the FPDC was off the charts for a stock 99 explorer, i was near 95% duty cycle at wot, @5500rpm, whoa not good. Figured i would bring her back in the garage and go look in my parts closet sure enough i had a spare motocraft fuel filter. score! took all of 5 mins to install after removing the fuel pump fuse (to prevent gas spray) and starting the truck until it depressurized the line. while i was also under there i threw on a gibson swept side exhaust that i have been meaning to install. 2 things, upon startup i noticed, one it sounded pretty good, and 2 the idle was Absolutly night and day difference!! I figured i would take the truck for a little drive and check it out. once again i data logged the truck and this time i saw a much much nicer duty cycle in the 70's, ah problem fixed! previously i was getting 12mpg 99 175k 4.0 SOHC motor - all origional, basic matience ect. i took the truck on a 200 mile round trip to and from nyc two times, and all i can say is wow, i went from 12mpg to 18mpg! if you are questioning if your fuel filter needs to be replaced or has over 40k on it, i suggest doing it as cheap insurance, now you may not get the milage gain i did (as mine was most likely origional, and when poured into a container it apeared that rust was coming out of the filter) but for how cheap and easy it is to replace i would highly reccomend it, as it is an item that is often overlooked.

 

[2000StreetRod]

fuel pump duty cycle

I assume there is a PID for fuel pump duty cycle that you datalogged. I wonder how it is computed. The only access the PCM has to fuel pump data is the voltage at the fuel pump relay on the side connected to the inertia fuel shutoff. I thought the relay stayed energized (closed) any time the engine is running and the fuel pump ran continuously with the excess fuel dumping into the fuel tank. I suppose the load on the pump varies with flow which could be reflected in the voltage read by the PCM.

Good job on replacing your fuel filter! I suspect clogged filters shorten the life of the fuel pump.

 

[Vinson581]

the explorers are a returnless style fuel system meaning the pump only takes what it needs, and varys voltage to compensate flow. (unlike say an aeromotive fuel setup on a high hp car where the pumps runs @100% duty and the fuel unused at the rails goes back to the tank). now being returnless this means the pump only takes what it needs, and varys voltage to compensate flow. the pump gets its imput from a fpdm, (fuel pressure driver module) which in turn gets signal from the ecu and tps taking into consideration engine rpm, and spark advance, then sends the signal to the fpdm telling it how much voltage to give the pump. most obdII fords are setup this way. hope this better explains where the PID reads from!

none the less my milage is better!

 

[2000StreetRod]

fuel pressure driver module?

I understand the concept you described but the Ford Wiring Diagrams for my 2000 don't seem to support it. I agree the PCM monitors the TPS but there is no way for the PCM to control the voltage to the fuel pump. The only electrical connection I can find between the PCM and the fuel pump is PCM Pin 40 (Fuel pump relay input). It allows the PCM to monitor the voltage of the path from the fuel pump relay output to the fuel pump via the inertia fuel shutoff. If there is a fuel pressure driver module it would have to be located in the fuel tank and be independent of external control. The photo below of a fuel pump assembly was posted some time ago by ranger7ltr.

I have an SCT SF3 and would like to investigate further. What is the name of the PID you datalogged for the fuel pump duty cycle? It might be useful for identifying a "tired" fuel pump as well as a clogged filter.

 

[2000StreetRod]

3rd Generation with fuel pump driver module

I did a search for "fuel pump driver module" and learned according to the following thread that it was implemented on the 3rd generation models.
Fuel Delivery Issues ***SOLVED***
I'll have to see if I can find one on my Sport but didn't notice one when I dropped the fuel tank. It doesn't show on any of my wiring diagrams.

 

[Vinson581]

i will upload a picture of a screen shot from my SCT software

but i do belive only 99+ explorers have a returnless fuel system.

im very interested now as well as to how it is reading the duty cycle, because it is clearly reading it and varying with rpm and engine load.