Hey fellas,
I've been diagnosing this issue for 3 days during my commutes between job sites, and I think I know my issue. But let me spell out my detective work...just in case someone else experiences this.
Last Friday I replaced the brake line behind the fuel tank, so I pulled the fuel tank out and replaced the hard line within about 3 minutes. Pice o' cake.
I was not surprised to find my sending unit lacking the rubber suction boot on the supply side of the sending unit, it's resting on the bottom of the tank in several disintegrated pieces. So I whipped out my roll of 5/16" rubber fuel hose and cut a section out. I used a utility knife and cut 4 V's on the end so it wouldn't suck itself to the bottom of the fuel tank. Everything went back together very well, maybe too well
I lost prime in the fuel system over the weekend, so it took a bit of cranking Monday morning to get my fuel back up to the engine. It ran fine Monday, but I had a new problem arise. At random times, it seemed to suddenly accelerate on its own, like a Runaway engine.
3 thoughts instantly crossed my mind:
1) I'm running out of fuel and I'm getting air in the system for that sudden boost (which is what it's like when you run out of fuel). This would explain the loss of prime if the supply line wasn't totally emerged in fuel in the tank.
2) My mechanical fuel pump is on its way out, and it's de-fueling and then pumping too much fuel to advance timing or the cold timing advance had a poor electrical connection on the pump. That's how drastic the sudden boost has been feeling, as if the cold advance was switched on. If the pump is shot, that would explain the loss of prime.
and 3) My CDR was recently cleaned (soaked in gasoline, then allowed to air dry) about a month ago, but there is oil on the bottom of my intake on the interior, so maybe the burning oil was causing my sudden acceleration boost. But that doesn't explain the loss of prime.

Over the last 3 days, I've narrowed it down by running various speeds and RPM's and played around with idle, light acceleration and hard acceleration.
I decided to change out hose with 4 V's cut in it, and made another length that only has 2 v's cut into it. The hose has a natural curve from being rolled up that it very nicely lays parallel to the bottom of the fuel tank and actually lays on the bottom perfectly.
Yesterday I determined the boost was coming from a 1/2 pedal sudden throttle increase. If I got into it about 1/2 throttle, it would suddenly "boost" and go faster. I played around driving "with the boost" and determined maybe I like it! And at this point I was convined it was the oil burning from the CDR.
Until today when I hit a hill, dropped it in 3rd at 35 MPH and stuffed the pedal to the floor and held it. Within 10 seconds of WOT, I went from 35 to 55, and then I started "boosting", but then affter maybe 2 seconds of "boosting", it began de-fueling. I experimented by keeping my foot to the floor.
At this point, I dropped from 55 MPG (nearly on the govenor, which is 60 MPH for my 3rd gear) down to 35 due to a lack of fuel. My natural insticnt was to give it more fuel so it stayed running, but I instead shifted into 4th gear and let it idle over the crest of the hill. The engine didn't die at all, and slowly cae back to normal.
Mystery solved, I'm pretty sure the rubber hose is collapsing onto itself under hard throttle sucking pressure...even with just 2 v's cut into the end of the rubber hose.

My plan is to cut a short 3" section of 3/8" brake line and cut 2 V's in the steel brake line, inserting 2" of it into the rubber hose and using a hose clamp to secure it to the hose.
My question right now is how the steel hose clamp will react with the diesel fuel? The hose clamp I have is pretty shiny, but seems to be made of standard steel. The section of metal brake line I have is painted with green, I'll just grind that off so it's bare metal. I'm sure it won't rust seeing how diesel is an oil.
Anybody have an opinion on the reaction?

 

Could be the V's you cut are allowing the ends to flap down over the opening. Your insert of metal tubing will prevent that from happening.

Corrosion has to have an electrolyte to carry the reaction and give the electrons a place to go. The basic reaction is Fe --> Fe3+ + 3e-. In other words, when the iron corrodes, it gives up electrons. Then the positive charged iron ion reacts with a negative chaged oxygen ion. Making iron oxide as the result. But diesel fuel is not very good of a conductor, and you don't really have any oxygen present. The stainless steel will not corrode, the metal tubing will if they are in dircet contact. However I think each piece is separated by the rubber, so there is no galvanic couple. In the end this all means, just clamp the tubing in and it should cure your problem. You will nto have any corrosion issues.

 

hey i have the same problem with my new rear tank.
luckily i can just lift the dump to inspect.
my sending units metal line is rusted and sucking air.
that is a cool "boost" feeling until it looses fuel.
i don't see any problem using metal fuel line as the pick up hose.MASS roads will eat the truck around the metal fuel line in your tank and propably still be good when she's on her way to the scrap yard.......hopefully a year or two from now tho.

 

Mine has a problem with the front pickup tube as well. I just never run it low enough to find out what would happen. I guess I'm the smarter one of the bunch.

 

Fabulous! I didn't have a clue that's how corrosion worked, thanks!

Yeah, the "boost" is pretty sweeeeeeet!
I have a lot of room under there also, I have 12" betweent he frame and the bottom of the flatbed deck. But, once again, you can just lift the dump bed and there it is
Yeah, the salt is nasty...but this truck is in incredible shape. I have several galons of ACE Gloss Black enamel in the garage waiting for a nice summer day to keep it nice

I know exactly how you mean, I don't have a working fuel gauge...so every 200 miles I filled up to make sure I didn't get too low. On a side note, I swear the speedomer is the only gauge that is actually good in these trucks. These gauges are useless pieces of ****! The original gauges in my '65 work, why can't 20 year old newer gauges be good? LOL



There it is:


And my solution:


I had the sending unit off the newer tank I installed. But that sending unit had a rusted line on the sending unit, so it was patched together with a rubber fuel hose on my last truck. I used the good unit on the right, and transferred my rubber hose over to it. That's the hose I did on my first truck, the one I added 2 more V's to in order to get 4 V's. I'll cut a short section of 3/8" brake line and clamp it on the hose I currently have installed. The nice part is that the job only takes 5 minutes because I have a lot of room under the deck and above the tank. Guess I'll go do that now so I can drive between jobs confidently tomorrow!

 

Get a turbo and you can feel boost every day!!!

 

Done, success!
Drove on a few flat roads and gave the different RPM's for various simulations, then hit a hill HARD and it's awesome!
Today I ended up sneaking 45 minutes between jobs and put in a used lift pump and a nicer "used" air cleaner. The one I had is like dark brown, and the used one I put in is still probably not good, but it's better.
No running start for this hill. Started across the intersection, shifted into 2nd, floored it. Tires let go, backed out a bit and got her up to the governor, then hit third and floored it the whole length of the hill. From 35 to 60 on the governor and no "boost" kicked in! Just kidding, I'm thrilled I'm back to having a trust-worthy truck again.

Snap on, I can't wait for the turbo'd 6.9 in the '65

 

i went a little further on my pickups...I fabbed up some aftermarket strainers....Haven't had a problem yet. To see you can check out my old posts/pics even David said they were pretty awesome. The best part once on E, I can still go around 20 more miles before stumbling and have no choice but to switch tanks!!!!

 

Double Zero, I'm linking your thread here and I'm linking this thread there. Got it? LOL!

Your pictures are excellent, and I think your thread will be a good addition as a link to this thread for anyone who may stumble upon this in a search. Nice job!

https://www.ford-trucks.com/forums/8...rear-tank.html

 

hey good going.
my problem is a little different.the top metal line that goes into the pickup is rusted and has pin holes.i see them bubbling/sucking air with the truck running.
i see AZ sells what i need to fix this,but do you happen to know how these are held in place blue?

Help/5/16 x 4 in. double bead fuel sending unit repair line and 90 degree end (800-229) | Fuel Sending Unit Repair Kit | AutoZone.com

Help/3/8 x 4 in. double bead fuel sending unit repair line and 90 degree end (800-230) | Fuel Sending Unit Repair Kit | AutoZone.com

can i simply remove these lines? are they just press fitted do you,or anyone know?
hope ya don't mind me asking in your thread,since you seem to be all set now,and it's all kinda the same topic.
maybe i have to take the pickup/sending unit and those parts to someone to have them replaced?

 

Dude, these gauges aren't bad, all mine work just fine. You sure its not like a fuse(I don't even know if they are on fuses)? You check all the wires?

 

The 3/8" brake hose inside the rubber hose didn't fix the issue.
But there's another factor that hasn't been an issue yet, but I fixed it today. When I did my rear axle swap, I dropped my rear tank and never put it back. I don't need it, the extra fuel tank only adds more weight and I just don't want the hassle of a leaky tank selector valve.
Of course, I just left the lines that go to the rear tank hanging there...knowing that eventually I will be running new fuel lines and would take care of all the lines at that point in time.
Well, I just cut the plastic slip-on ends off my plastic lines and put 3/8" fuel hose over them...connecting the front tank supply and return tot he engine side of the valve...totally bypassing it.
So far, a 30 minute test drive with all the possible RPM/speed situations turned out positive. But of course, last night's test drive with the metal pick-up was good too....
I'll find out in the morning on the way to work...

 

F250, ask all the questions you want!! I've got a second sending unit in the garage I can closely examine in a few minutes.
That particular sending unit came from my first truck, and has the same pinhols as you have. My solution was I RTV'd the whole metal stem...then after it dried, I put a piece of fuel hose over it and clamped the crap out of it. It never gave me any issues.
Those are AWESOME links you have!! I imagine they are pressd and soldered, but there's nothing a cutting wheel can't remove. Then use a punch/chisel to pound the rest of it out? Or a drill? I'll let ya know in a few minutes!

Snapon, mine are 80-86 body style, yours are 92-97 body style. My temperatre gauge is the only one that "might" work, as it kind of resembles what I usually assume the engine temp to be.
On any given day, within a 5 minute time period, I can glance at the dash and see the fuel gauge pegged PAST F (knowing in my head that I filled up 4 days ago, it should be more like 1/4), then I can watch it move down to 1/2, then back up to 3/4, drop down to PAST E, shave violently as if there is NO fuel at all, then suddenly it can dart right back up past F again. There's no pattern to it, the needle is just "exercising" I suppose LOL
At some point I'll be taking a piece of aluminum cut to the size of my dash insert and installing all mechanical aftermarket gauges
Kind of like this one from Dave S's gallery...I don't know if this is Dave's truck, but it's what mine is planned to look like someday

 

Oh, I forgot that detail. Well, my gauges do work well and I like em'. They all read accurately, so no reason to yell at them(fingers crossed). I like that custom gauge cluster too, Looks awesome.

 

my speedo is the only guage that works as well