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Discussion Starter · #1 ·
alright guys, still having the same problem i told you about before. 84 f350, 6.9l while driving the truck for about 5 minutes, my fuel filter is sucked dry. have a frame mounted electric pump, steady supply of fuel is getting to the fuel filter. cannot find any kind of blockage anywhere. the whole fuel system has been taken apart, new fuel lines and clamps, auxiliary tank, the whole sha-bang.
the only thing i think can be done here is to remove the filter assembly. have to figure out how what to do with the return line. i have a filter before the pump now.
any advice would be greatly appreciated.
 

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my fuel filter is sucked dry. have a frame mounted electric pump, steady supply of fuel is getting to the fuel filter.
What your saying is kind of contradictory. If it's getting to the filter, then the blockage must be the fitting going into the filter, must be a large chunk of something blocking it. That should be a 3/8" steel line, unless you've changed it to something else.

Is this the filter you have?

The return line on the filter, if it's like this, is only to bleed off any air in the filter, you can do without it.

You should just continue with the same thread for the same problem. Who wants to hunt down what you said before.
 

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Discussion Starter · #3 ·
the return line comes from the #1 injector, part of the fuel return. It goes to the fitting that the supply line to the inj. pump is attached to.
After sending the original out this morning, i have taken all fittings and the flange assembly apart, cleaned, inspected, and reassembled using petroleum thread sealer. Yes, 3/8" line.
If this does not work, i see my only option to bypass the filter assembly altogether. have had this issue for going on 2 years now
 

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ongoing fuel issue

When you added the electric fuel pump, you bypassed the mechanical pump right?
 

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How much fuel pressure are you getting at the factory filter?
 

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Discussion Starter · #7 ·
don't have a pressure gauge, but when the filter is full and key in run position, pump is working fine. filling up 16 oz container in about 20 seconds.
 

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Does the new tank have a vent? Is the filter on the positive pressure side of your pump? Is your fuel pump plumbed wrong?
 

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Discussion Starter · #9 ·
yes the tank vented. the inline filter is before the electric pump. the filter assembly on top is arrowed correctly. the electric pump is on the frame rail under the driver side.
 

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the return line comes from the #1 injector, part of the fuel return. It goes to the fitting that the supply line to the inj. pump is attached to.
In NO way should that return line from #1 injector be connected to the supply line to the IP. That 5/16" steel line must be direct from filter to the IP with nothing else attached to it.

That return line from #1 injector has to be connected ONLY to the filter orifice fitting, as shown in the pic I posted before.

If you can't see where from the pic above, I will snap another pic larger, and label it.
 

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Im thinking that filter seal may be better at pressure than vacuum. Anyone else care to comment?
 

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Discussion Starter · #12 ·
my bad Bill; yes it is connected to the orifice on the engine side of the filter. told you wrong on that. have changed out the filter 2x. the whole flange assembly has been changed also. the fuel line fittings have to be used, can't find any fittings with those thread patterns. been told they are a different type of thread.
your pic was too small to see clearly.
in order to bypass the filter assembly, have to figure a way to incorporate the orifice fitting for that line from the #1 injector. this is the only way i can think of to see if the filter is the problem. anyone care to comment? ?
 

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I said, that return line from the filter to #1 injector don't mean SH*t. It just relieves any air in the filter back to the return lines. You can eliminate it if you want to bypass the filter.

You can put a clear line in place of the black rubber hose, that way you could see if there is in fact air coming out of the filter. Most any hardware store carries the clear line. Get a couple of feet of 1/4" ID and the thick walled, make a loop in it, air will settle at the top of the loop and can be clearly seen.

I just don't understand why the filter is going dry with an electric lift pump. The IP will suck/draw fuel from the filter if it is not continually supplied with fuel with the engine running until it runs out of fuel.

It's got to be some how or some way the lift pump has quit supplying fuel to the filter.
 

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Discussion Starter · #14 ·
this problem has me bonkers. will try the clear hose and see what happens. will probably be the weekend though, got lots of work to do.
 

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Also, as I think chuckster was alluding to, your lift pump needs to be able to keep up with your injection pump. If you have another pump, or the mechanical one still works, you might just want to give it a try.
 

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Discussion Starter · #16 ·
the problem originally started with the mechanical pump. not a bad idea to try the mechanical again. yes the mechanical pump has been replaced also. will check what the flow of the electric pump is.
 

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Discussion Starter · #17 ·
well guys, just spent the last hour or so working to bypass the OEM filter; truck fired right up ran smooth in driveway for 10 minutes, put on road; less than a mile away it stalled out. acted just like it has been doing, like its running out of fuel. turned the key off and back on waited about 5 seconds, turned it over, and about 10 seconds after that it slowly came to life.
don't know the next step, guess i'll start saving money to get it in a shop and let someone who knows more than me look at it. that may take a while though knowing the cost of diesel repair now.
Any suggestions ? ?
 

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Take the rail filter off, put the stock filter back on and test. Post results.
 

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Discussion Starter · #19 ·
going to put it back to factory, (remove electric pump, hook up mechanical). then go from there. Chuckster, can tell you now there will be no change in the way it acts. been working this problem too long. you guys just need to be here, you can drive it and experience it for yourself.
will let you know when it is back the original way.
 

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Would it be easier to try it with a pressurized filter system than a filter system under vacuum?
 
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