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Fuel tank/sending unit problem? A back siphon on fuel filter return line emptied my fuel tank.

ben_2_go

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I changed my fuel filter yesterday. I had just over a half tank of fuel. When I removed the fuel filter, gas never stopped running out of the return line from the filter back to the tank. I stuck the fuel line into an empty jerry can and took the old filter with me to get a new one. When I returned home, the entire contents of my fuel tank was gone, except the little over 5 gallons my jerry can held. This isn't the first time I've changed my fuel filter. It's about the 5th time since I bought the truck in 2003. I never had it lose fuel through the lines after the filter was removed. I do have a Spectra replacement sending unit I installed 3 or 4 years ago due to a failed fuel pump. I opened the fuel filler cap to check the tank for pressure and there was none. I put the cap back on. I thought that there were check valves in the sending unit to prevent back siphoning of the fuel system in case of an accident. Has anyone experienced anything similar? Is it normal for the return fuel line to create a back siphon? My truck was flat on the ground not raised in the rear like I've seen some people do it.
 


dirtymike

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I dont have the answer but i sure wish someone in here did. I have the same problem every time i change my fuel filter unless I'm changing the pump at the same time. I dont lose 5 gallons though.
 

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That's seems crazy, I've never seen that. just a little dribble from the filter.
 

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The return line goes to the bottom of the gas tank, but thru the Fuel pressure regulator(FPR), 2001-2011
FPR valve may be the issue, it should be closed with pump off, i.e. pressure is under 60psi at FPR(hose from filter)

But it may not close fully unless there is some pressure applied, i.e. 10-15psi, don't know

What is happening is just a siphon effect, the hose end at the filter is lower than the bottom of the tank and fuel level in the tank, so current fuel in the return line drains out and pulls in new fuel from the tank as it does, siphon

So the siphon starts when you remove that hose at the filter, and its sucking fuel from the bottom of the tank, so will drain the tank

Just raise the end of the hose up as high as possible to get air in that line, to stop the siphon effect, then it won't leak any more fuel when it's down lower
 

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That's seems crazy, I've never seen that. just a little dribble from the filter.
That's the way mine was until I installed a new spectra sending unit several years ago. I never had running issues until a few weeks ago. I now suspect the sending unit but also the head. Fail compression test and endoscope showed what appears to be cracking between the valves, also valves have receeded into the head. My machine shop says that once the valves receed into the head, it's done. No rebuilding is possible.



The return line goes to the bottom of the gas tank, but thru the Fuel pressure regulator(FPR), 2001-2011
FPR valve may be the issue, it should be closed with pump off, i.e. pressure is under 60psi at FPR(hose from filter)

But it may not close fully unless there is some pressure applied, i.e. 10-15psi, don't know

What is happening is just a siphon effect, the hose end at the filter is lower than the bottom of the tank and fuel level in the tank, so current fuel in the return line drains out and pulls in new fuel from the tank as it does, siphon

So the siphon starts when you remove that hose at the filter, and its sucking fuel from the bottom of the tank, so will drain the tank

Just raise the end of the hose up as high as possible to get air in that line, to stop the siphon effect, then it won't leak any more fuel when it's down lower
I was thinking the fuel return was what Ford used to restrict fuel to build pressure. So that may be part of my issues. Pretty familiar with back siphioning. I was a pilot and aviation line service tech. It was an issue on high wing aircraft with wing mounted tanks. We regularly inspected the fuel lines during preflight inspections. We had vermin eat a fuel line on a Cessna and dump 180 gallons of av gas all over the tie down lot.
 

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What is the fuel pressure supposed to be for an early 2001 with a 2.5L engine? I've read everything from 45 to 72 psi. My shop manual says between 55 and 62 psi.
 

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I have a length of hose capped off and place it secure with the clip.
 

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1998 and up Rangers used 55-65psi fuel pressure spec, 1986 to 1997 30-40psi

1998-2000 didn't use a return line at all, 2 port fuel filter, FPR was in the tank but on the Fuel Pump's OUT line
This did not work well, pressure at the injectors was not very stable

Ford added a return in 2001(but can have it in 2000 as well) at the fuel filter, 3 port, and same FPR is in the tank but on the added return line not on the pump OUT line
Works way better to get stable pressure at the injectors
 

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1986 to 1997 30-40psi for an indefinite period of time? Where is the most possible place for a bleed down to start rather rapidly?
 

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That's running pressure spec
Key off spec is usually 50% or more of running pressure

Outside of a broken fuel line there are only 3 places pressure can leak down when key is off
FPR, on the engine, or in the gas tank(depending on year)
Fuel pump
Fuel injector<<< this is usually pretty obvious from running issues

With the 1986 to 1997 simply cycling the key on one time should give your system 10psi so enough to start engine, although it may stall after startup but should restart normally after that
 

ben_2_go

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My 2001 2.5L runs 62 psi and doesn't even shake the needle when the throttle is slammed to the floor from a dead stop. It ran like crap though. I've ruled out the fuel filter and fuel pump. I found my problem. I have the misunderstood and heavily misdiagnosed receded valve problem. I'm trying to decided if I want to buy a new head casting and build a new head, because remans are janky at best because of the receded valve problem. I've run into this as well as some other people I know that have bought rebuilt heads. The bottom end is having issues and needs a rebuild. The truck is an all around beat and I'm not sure if it's worth it to rebuild or scrap it. I can't afford the insane prices of used or new trucks.
 
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sgtsandman

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My 2001 2.5L runs 62 psi and doesn't even shake the needle when the throttle is slammed to the floor from a dead stop. It ran like crap though. I've ruled out the fuel filter and fuel pump. I found my problem. I have the misunderstood and heavily misdiagnosed receded valve problem. I'm trying to decided if I want to buy a new head casting and build a new head, because remans are janky at best because of the receded valve problem. I've run into this as well as some other people I know that have bought rebuilt heads. The bottom end is having issues and needs a rebuild. The truck is an all around beat and I'm not sure if it's worth it to rebuild or scrap it. I can't afford the insane prices of used or new trucks.
I’m not sure what kind of mileage engines you can get now but when I swapped the blown engine in my ‘98, I was able to get one with about 100 K on it a number of years back and just swapped what needed swapped to make it work with a manual transmission. That engine is still running in it. The body is rusted to hell but the current owner is still running it.
 

ben_2_go

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I’m not sure what kind of mileage engines you can get now but when I swapped the blown engine in my ‘98, I was able to get one with about 100 K on it a number of years back and just swapped what needed swapped to make it work with a manual transmission. That engine is still running in it. The body is rusted to hell but the current owner is still running it.
I can't find 2.5L engine in my area. The ones I know about are the ones that are on the road and still running good.
 

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You can also use a 1995-1997 2.3l Lima, not earlier
Same engine, 2.5l is a stroked version, so different crank and connecting rods, but same pistons, head and block
Plug and play
 

ben_2_go

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You can also use a 1995-1997 2.3l Lima, not earlier
Same engine, 2.5l is a stroked version, so different crank and connecting rods, but same pistons, head and block
Plug and play
Those heads are the same as the 2.5 and suffer the same problems. It goes back to 93 when the D port heads came to be used on the 2.3 and later 2.5.
 

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