FUEL FILTER

[Alwaysreadyrob]

1994 7.3 turbo diesel, dash says FUEL FILTER when on front tank, spin on filter is new .
Are there in tank filters on these trucks ?

 

[gandalf]

I don't believe the '94 has an in-tank filter. I know my '92 does not.

As far as I know the "Fuel Filter" light is measuring fuel pressure. That being the case your front tank is producing a low pressure situation. Since the rear tank is fine, I would guess that the front tank has a blockage of some sore. It could be in the tank, in the short line, tank to FSV, or in the FSV itself.

 

[Alwaysreadyrob]

What’s an FSV ? Fuel Sending Valve ?

 

[chillman88]

A bad lift pump can cause it too.

FSV is the tank switching valve on the frame rail that switches between front and rear tanks.

 

[Alwaysreadyrob]

Thanks

 

[Selahdoor]

A bad lift pump can cause it too.

FSV is the tank switching valve on the frame rail that switches between front and rear tanks.

But if it was the lift pump, it wouldn't matter which tank was selected.

 

[chillman88]

But if it was the lift pump, it wouldn't matter which tank was selected.

Good catch, I missed that.

For what it's worth, my front tank does the same, because it sucked up some pieces of the old showerhead pickup. One of these days I might drop it and fix that....

 

[Selahdoor]

Good catch, I missed that.

For what it's worth, my front tank does the same, because it sucked up some pieces of the old showerhead pickup. One of these days I might drop it and fix that....

Exactly what I was thinking the most likely cause of the OP's problem was. And yeah, I'd probably have the same attitude.

I eliminated the showerhead on my front tank, while I had it apart. Hung a piece of vinyl tubing, with a brass tee on the end, in it's place. Adjusted the length perfectly so the tee sits directly above the bottom of the tank without quite touching it. Easy to do, with the tank out. Stick a flashlight in the filler neck of the tank. And look through the hole where the rollover valve goes. You can see exactly where the float and the end of your tube is.

Yeah, that means there is no filter in the tank. But I don't make it a habit of knocking crap into the tank when I fill it up. And that is what we have a fuel filter for, in the first place.

Way I see it, with the full diameter of the pipes and hoses, and the openings through the FSV, it will take a pretty hefty chuck of crap to plug it up. And the only place I have ever seen chunks that big, coming from in a tank, is from a crumbling showerhead.

Leaving the showerhead in means eventually you are going to have this problem. Plus, the 'filter' on the showerhead can be clogged with smaller pieces of stuff. Granted, that is why the thing looks like a showerhead. More filter area to clog, before there is a difference in flow. But like I said, the sort of stuff that would clog the showerhead will NOT clog the hoses and FSV. But will be caught in the fuel filter...

 

[raydav]

Regarding supply/lift pumps causing problems. I have so far not proven to myself that we even need one.

For about 27 years one of these pulse pumps was my supply/lift pump. Several times I drove without the pump running and the engine did not seem to notice. But those pumps, when not running, are just a check valve.

New photo · Saturday, Oct 5, 2013 📸

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I recently switched to one of these rotaries. And drove away with it not running. What caught my attention was the exhaust smoke because the turbo scavenge pump was also off.

New photo · Saturday, Sep 30, 2017 📸

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And my shower heads and in-tank pumps that break up are all gone, replaced by rubber hose.