Am I on the right track?

IDIBRONCO

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Not a direct answer, but first off, I wouldn't use too much air pressure. When I've done it, I used line pressure, but only held the pressure on for maybe 3 or 4 seconds at the most and then let it bleed off. That leads to my second suggestion,. If you do blow compressed air back through the fuel lines, remove your fuel cap first. This will help to keep from overpressurizing your fuel tanks. If you keep the air pressure on for too long or have the tanks fairly full while doing this, you may actually blow fuel back out of the filler neck. Just another reason to use short bursts of air.
 

asmith

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Not a direct answer, but first off, I wouldn't use too much air pressure. When I've done it, I used line pressure, but only held the pressure on for maybe 3 or 4 seconds at the most and then let it bleed off. That leads to my second suggestion,. If you do blow compressed air back through the fuel lines, remove your fuel cap first. This will help to keep from overpressurizing your fuel tanks. If you keep the air pressure on for too long or have the tanks fairly full while doing this, you may actually blow fuel back out of the filler neck. Just another reason to use short bursts of air.

Thanks for the reply. i was definitely going to take the cap off when i did it. and I was only going to use shorts bursts like you described. what do you mean by "line pressure"? like is 50 psi too much? should it be more like 10 psi? i know this is not a high pressure system and i don't want to blow anything apart.
 

Clb

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-10 to be safe, if you have showerheads ya could blow em off\apart.
or crack a line ect.
 

Clb

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Yepp
That is why I mentioned -10 psi...
My line psi will hit #250, regulated to 125.
Subtle input like you mentioned works fine (if ya understand)
 

asmith

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ok so a little update. The issue seems to be somewhat heat related. When it first started happening we had temps over 100 for about a month. It dipped into the 90s for about a week and it got slightly better. Then last week it went back to over 100 and it got way worse. To the point where can't even run at over 2000 rpm on flat ground or it kicks the fuel filter light on. That is a bummer on the freeway with 4.10s.
So i finally had to make some time to really dig into it. Started at 9 tonight-cuss-cuss First thing I did was see how much the pump was putting out. Ran a hose into a bucket, and it took about 2:15 to put out half a gallon. that seems really slow to me. The rating on the pump is 140 gph. So doesn't that mean it should be doing about 2.3 gallons a minute?:dunno put my new pump on thinking I had found the problem, it did the same thing:frustrate Now I am second guessing myself on if this is a useful test.

So I crawled under the truck and bypassed the FSV thinking that would be the next most likely problem area for a blockage in the line. What a PIA that was. I used 3/8" hose, but it seems like it is too big for the metal lines. Really had to crank down on the clamps. Is there a better size to use? Tried my test again and if anything it was slightly slower out put.

Now I am at a loss as what to do. l thought about buying a bunch of hose and skipping all the hard line from the tank all the way to the pump, but i don't want to just throw money at it blindly.
Oh and i did all the tests with the cap off the tank to rule out vapor lock and it pulling a vacuum on the tank.


Any bright ideas out there?
 

The_Josh_Bear

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Hey that's good progress! It isnt what you want to see but at least you've proven that you aren't getting even close to the GPH you should have.

How does the filter screen on the pumps look?

Before getting too much further I'd triple check the ground and power to the fuel pump for good clean connections.
The next thing I'd do is isolate the pump with two buckets, take another GPH test. That removes the supply system from the equation. If the GPH is good then run a new supply line.

5/16" hose is the next size down for the hose to fit over the hard line. Also the FSV is indeed a PITA, I agree completely.
 

The_Josh_Bear

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I just did the math and your pump is rated at just over 10 TIMES the throughput you're getting out of it. Yikes.

Where is your pump mounted?
 

asmith

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I just did the math and your pump is rated at just over 10 TIMES the throughput you're getting out of it. Yikes.

Where is your pump mounted?

That is a good thought to pull the supply from a fresh bucket. I hadn't thought of that. I will do that today.

The pump on there is brand new and the screen is perfectly clean. When I mounted it for the test I just ran wires directly to the battery. The permanent setup is mounted off of the filter head using a solenoid.

yeah the flow volume just seems really low to me. It makes sense that it couldn't keep up with the engine under high load scenarios.
 

The_Josh_Bear

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Crap it just dawned on me that using a battery on a vehicle that isn't running is lower voltage than with it running. You should still have ~80% flow though, not >10%.

That leaves a supply issue OR a bad pump issue.
 

asmith

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ok so some corrections. the pumps are only rated for 33 gph. There are a couple places on line that say 140, but they are less than reputable. Guess that is what i get for searching late at night on my phone. Looking at the manufacturers page they are rated for 33gph which is still more than twice the rate I am getting out of them. ON to more testing.
 

asmith

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new update. Thanks to @The_Josh_Bear for the idea. Ran intake from a container of fuel, and the pump put out the same volume in less than half of the time. This leads me to believe there is a block somewhere down the line. I also for the first time saw a few flakes of what looked like rust in the container from last night. -cuss:frustrate

My side tank already was blocked at the fsv from something, I am guessing rust now, and now it looks like my back tank is having a similar issue.
I am thinking a full replacement is going to be in order to fully get rid of this issue. I am thinking of going with a bigger back tank and getting rid of the side tank and FSV completely. I know it eliminates the spare but I don't carry one anyway. Who has done this and how do you like it? When it is full is it a lot of weight back there?

what should I do for fuel lines? I think i just want to get rid of what is there and go all new so I don't have to worry about them. Is just rubber lines good enough or should i swing for braided AN lines?
 

The_Josh_Bear

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Good to know the pump works at its rated GPH and you're on the right track now!

I have the bronco 38 gal tank and I love it. The only thing about it is you'll need to extend your pickup tube with fuel rated hose, and extend the fuel sender arm with stainless wire or whatever you can figure out. The best solution I heard of was a member that used a length of SS tig wire- I thought that was really smart.
And lastly the mounting hardware that comes with it wont fit, you'll need your own longer bolts and matching nuts, and dont forget the blue thread locker!

Any hose on your pickup that touches diesel should be fuel-rated. They are specialty rubber compounds like vinton, and wont degrade even if submerged into diesel. It's not cheap either, you might want to drop your tank and see what the situation is before blowing $100 on fuel hose when the hard lines are fine but it's the pickup that's clogged. Just thinking out loud a bit, haha.
 

asmith

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Yeah normally i would agree with you, but I need the truck for work. When its not working I am not making money and customers are not happy their projects are not moving forward. SO this will be a gather all parts one could conceivably need and then drop the tank and do the repair type job. that way i have as little down time as possible.

I also am of the thought, if I am in there now lets upgrade if possible so i dont have any more problems with it. though you could argue the system is 24 years old, hard to beat that.

If your tank is full do you notice the extra weight in the back like that? was it hard to bend the arm to get it to read correctly with the bigger tank? that seems to me the only tricky part.
 

The_Josh_Bear

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I hear you there, gotta have work. Gotta have the rig!

It's not hard to bend the arm. If all you do is bend it, you wont have full travel. Itll read full for half the tank then start to move towards E. (And may not have the length to make E very accurate, but I cant remember. It may actually straighten out to get near the bottom OK.)

Using a new and longer wire would allow full use of the sending unit. I have a hole in my float so it doesnt work and I have gotten so used to driving by the trip meter that I haven't gotten around to fixing it, haha. Which is pathetic since the PO literally cut a hole out right in the bed above the rear tank. I have better access than anyone and still haven't fixed it. Lame! Now that I own some SS tig wire though, I really should get after it. Bought a new float that has been doing nothing for 4 years too...doh. Ah well.

To clarify on the fuel pick-up extension: get rid of the stock "shower head" style pick up. Just use fuel hose and run it to the bottom. Cut a big V out of the very end of it so it cant suck to the tank.
I did that, and when I forget to switch tanks until I'm pumping air into the engine :angel: I can fill up that rear tank with 36.xx gallons. So it works great!
 

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