New fuel tank and sending unit weirdness (Questions)

classic Classic list List threaded Threaded
27 messages Options
12
Reply | Threaded
Open this post in threaded view
|

New fuel tank and sending unit weirdness (Questions)

Rembrant
Gentlemen,

I installed a new fuel tank this past winter (Spectra Premium # F14A 16.5 Gallon), and a brand new sending unit (Spectra Premium FG75A). I tested the sending unit before I installed it in the tank, and it stroked the fuel gauge with no issue. So now for the past few weeks driving the truck, the gas pump cuts off and the fuel gauge only shows 1/2 tank. I don't know how much fuel is in there...I drive it until I hits Empty, and then refill it...today it took 8 gallons.

Previously, the old rusty tank and sending unit both worked fine. I could fill the tank until full, and the gauge worked perfectly.

So today I got wondering if I tried to gently force some more fuel in there, if it would actually take it. I got another half gallon in there maybe, without trying any further, and the gauge went a bit above 1/2 way on flat ground, but when I was going downhill or coming to a stop, the gauge would read almost full. Back on level ground it would go back to the mid-tank level or so.

Anybody know what's going on here? Should I try to force feed it a little more fuel again and test?

That leads me to my next question...if that does work, then what is wrong?

I reinstalled the plastic tube in the fuel filler hose (reused original hose). I just checked and it is still intact on the upper end. When you look down the hole, all you can see is that plastic tube.

The reason I am asking all this is, I'll be pulling the box off on Tuesday before sending the cab/chassis to the body shop, and if I need to do something with the tank and/or sender, etc that would be the opportune time.

Does that plastic tube really need to be in there?

What would stop the tank from filling higher (if indeed that is the problem)?

Or, is there just something wonky going on with my new aftermarket tank and sender?..
1984 F150 4X2 Flareside. Mild 302 w/GT40 heads, BBK headers, Holley 4bbl, XE256H Comp Cam, M5R2 5spd swap, Magnaflow full duals. Fresh Medium Blue Metallic in August 2019.
Reply | Threaded
Open this post in threaded view
|

Re: New fuel tank and sending unit weirdness (Questions)

ArdWrknTrk
Administrator
You might consider going with a later (Bricknose) fill assembly.
They reverse the vent and fill tube.

As for your sender... Idkwts.
It's a shame it won't read right when mounted in the tank.
Is it Motorcraft, or Chinese?
 Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with an Edelbrock 1826 and Performer intake.
Too much other stuff to mention.
Reply | Threaded
Open this post in threaded view
|

Re: New fuel tank and sending unit weirdness (Questions)

Steve83
This post was updated on .
In reply to this post by Rembrant
I'm not a fan of Spectra or Airtex, but I don't think the tank or sender is causing this problem.  Generally, filling problems are caused by the neck vent collapsing, or being kinked or out-of-place.  There should have been a steel support in the tank's fill nipple to keep the bottom of the vent tube up where it belongs.  Did you insert the tube into that support?

In any case, my first instinct is always to upgrade with newer (generally-better) parts.  The '87-96 filler neck is a direct replacement, with better venting (both in the neck & the cap), and better caps (tethered, if the grommet survives; and more ergonomic).



Walk softly and carry a BIG SIX!!!
https://www.supermotors.net/registry/2742#album
Memphis, TN, USA, Earth, Milky Way
Reply | Threaded
Open this post in threaded view
|

Re: New fuel tank and sending unit weirdness (Questions)

Rembrant
Steve83 wrote
There should have been a steel support in the tank's fill nipple to keep the bottom of the vent tube up where it belongs.  Did you insert the tube into that support?
There was a little loop there for it yes, and yes I did insert the plastic tube in there.

It never occurred to me to check the later trucks for a filler hose...I never see them in the junkyards or being parted out. I'll check around and see what I can find. With my truck being a Flareside, the styleside fuel filler is not a direct fit...they are different. Maybe the 92-up Flareside filler will work if I can find one.

In any case, I'll check the vent tube and make sure it is all OK.
1984 F150 4X2 Flareside. Mild 302 w/GT40 heads, BBK headers, Holley 4bbl, XE256H Comp Cam, M5R2 5spd swap, Magnaflow full duals. Fresh Medium Blue Metallic in August 2019.
Reply | Threaded
Open this post in threaded view
|

Re: New fuel tank and sending unit weirdness (Questions)

ArdWrknTrk
Administrator
This post was updated on .
In reply to this post by Steve83
Steve, my '87 came with the gray strap tether.
I 'upgraded' to the black caps with grommet retainer, from Amazon.

Motorcraft number FC 920 and MY Amazon price is $9.80.

The biggest difference is that the later fillers fuel goes down the tube and pressure vents annually.
With the bullnose fillers gasoline goes around the vent and the tube inside vents up the middle.
 Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with an Edelbrock 1826 and Performer intake.
Too much other stuff to mention.
Reply | Threaded
Open this post in threaded view
|

Re: New fuel tank and sending unit weirdness (Questions)

FuzzFace2
In reply to this post by Rembrant
Rembrant wrote
Steve83 wrote
There should have been a steel support in the tank's fill nipple to keep the bottom of the vent tube up where it belongs.  Did you insert the tube into that support?
There was a little loop there for it yes, and yes I did insert the plastic tube in there.

It never occurred to me to check the later trucks for a filler hose...I never see them in the junkyards or being parted out. I'll check around and see what I can find. With my truck being a Flareside, the styleside fuel filler is not a direct fit...they are different. Maybe the 92-up Flareside filler will work if I can find one.

In any case, I'll check the vent tube and make sure it is all OK.
Cory, you are right on the style side & flare side fillers being different.
The front tank on mine was a miss match of parts when I go it I just used parts to make it look nicer.
For the rear tank I can remember what all I used but again I used what I had and to make it look nice.

On the front 16 gal tank are you sure you got the right sender?
I ask because most list the same sender for both the 16 & 19 gal tanks and this is not right.
I have yet to test mine, well put 5 gal. of gas in the rear tank and it did move the needle hope to do the same on the front tank today.
Dave ----
81 F100 flare side 300 six/T18 project
http://cars.grantskingdom1.com/index.php/1980-Ford-F100?page=1
81 F100 style side 300 six/SROD parts truck
http://cars.grantskingdom1.com/index.php/1981-Ford-F100
Reply | Threaded
Open this post in threaded view
|

Re: New fuel tank and sending unit weirdness (Questions)

Steve83
In reply to this post by Rembrant
Rembrant wrote
...the styleside fuel filler is not a direct fit...they are different. Maybe the 92-up Flareside filler will work if I can find one.
Yes, I should have said for the same body shape & tank position.  I can't remember if dually filler necks are interchangeable with stepsides, but it's worth checking.
Walk softly and carry a BIG SIX!!!
https://www.supermotors.net/registry/2742#album
Memphis, TN, USA, Earth, Milky Way
Reply | Threaded
Open this post in threaded view
|

Re: New fuel tank and sending unit weirdness (Questions)

grumpin
If it’s not the vent, take a couple of gallons with you and run it till it’s empty, then see how much it takes to fill it.
Dane
1986 F250HD SC XLT Lariat 4x4 460 C6
1992 Bronco XLT 4x4 351W E4OD
1997 Mazda 626 LX 2.0L G25M-R
1998 Suburban LT K2500 454 4L80E
Oregon
Reply | Threaded
Open this post in threaded view
|

Re: New fuel tank and sending unit weirdness (Questions)

Rembrant
grumpin wrote
If it’s not the vent, take a couple of gallons with you and run it till it’s empty, then see how much it takes to fill it.
Hey Grumpin good idea. I will give that a try as well.
1984 F150 4X2 Flareside. Mild 302 w/GT40 heads, BBK headers, Holley 4bbl, XE256H Comp Cam, M5R2 5spd swap, Magnaflow full duals. Fresh Medium Blue Metallic in August 2019.
Reply | Threaded
Open this post in threaded view
|

Re: New fuel tank and sending unit weirdness (Questions)

85lebaront2
Administrator
In reply to this post by Steve83
Steve, the dually filler necks are actually very stubby so you may be correct, the bulk of my filler system is molded rubber hoses.

Bill
"Getting old is inevitable, growing up is optional"
Darth Vader 1986 F-350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator
Wife's 2011 Flex Limited
Daily Driver 1994 Taurus LX
Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413
Reply | Threaded
Open this post in threaded view
|

Re: New fuel tank and sending unit weirdness (Questions)

Rembrant
In reply to this post by Steve83
Steve83 wrote
Generally, filling problems are caused by the neck vent collapsing, or being kinked or out-of-place.  There should have been a steel support in the tank's fill nipple to keep the bottom of the vent tube up where it belongs.  Did you insert the tube into that support?
I suppose this is a stupid question, but what happens if you remove the plastic vent tube from the filler neck all together? If you ran the gas nozzle slow, theoretically it would be better without the vent tube, right? The vent tube is just to help you fill the tank at a faster rate?

I'm wondering if that little metal support in my new tank was too big and has allowed the plastic vent tube to push further into the tank?...Hmmm...

I'm going to check that, and if need be I'll bend that little support a little bit to make sure the vent tube stays high.
1984 F150 4X2 Flareside. Mild 302 w/GT40 heads, BBK headers, Holley 4bbl, XE256H Comp Cam, M5R2 5spd swap, Magnaflow full duals. Fresh Medium Blue Metallic in August 2019.
Reply | Threaded
Open this post in threaded view
|

Re: New fuel tank and sending unit weirdness (Questions)

Gary Lewis
Administrator
They say that no question is stupid if you don't know the answer.  And I sure don't know the answer to that one.  But I'll hide and watch to see the results.  
Gary, AKA "Gary fellow": Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker in front & 10.25 Spicer/Trutrac in back, & EEC-V MAF/SEFI
Reply | Threaded
Open this post in threaded view
|

Re: New fuel tank and sending unit weirdness (Questions)

Steve83
In reply to this post by Rembrant
Rembrant wrote
...what happens if you remove the plastic vent tube from the filler neck all together?
It's been decades, but I vaguely remember trying that, and filling being AGONIZINGLY slow.  But that's the worst that can happen - give it a try, and let us know what you observe.
Walk softly and carry a BIG SIX!!!
https://www.supermotors.net/registry/2742#album
Memphis, TN, USA, Earth, Milky Way
Reply | Threaded
Open this post in threaded view
|

Re: New fuel tank and sending unit weirdness (Questions)

Randy
In reply to this post by Rembrant
Rembrant wrote
Gentlemen,

I installed a new fuel tank this past winter (Spectra Premium # F14A 16.5 Gallon), and a brand new sending unit (Spectra Premium FG75A). I tested the sending unit before I installed it in the tank, and it stroked the fuel gauge with no issue. So now for the past few weeks driving the truck, the gas pump cuts off and the fuel gauge only shows 1/2 tank. I don't know how much fuel is in there...I drive it until I hits Empty, and then refill it...today it took 8 gallons.
How did it work before the last few weeks? I ask because I installed a new tank and the same sender that you installed. The first fillup took a full 16 gallons (the 5ish were put in at my friend's hangar and the 10ish we put in when we drove to town) but the gauge didn't read. I was not as smart as you and didn't test it before I installed it. So I managed to remove it without dropping the tank thinking I'd confirm that the sender was bad. But it worked just fine outside the tank. I bent the wire a bit to get it to register higher; now it reads 1/2 tank when I fill up, but I never put more than about 7 gallons in because it feels so weird driving on E, even though I suspect that when I get to E I still have another 8 gallons.
1984 F150, 300 Six, C5
Reply | Threaded
Open this post in threaded view
|

Re: New fuel tank and sending unit weirdness (Questions)

Gary Lewis
Administrator
Make sure your tank is grounded.  And, to test your gauge, ground the Dark Blue/Yellow for the front or Yellow/Light Blue Hash for the rear.  With the key on the gauge should go to Full.
Gary, AKA "Gary fellow": Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker in front & 10.25 Spicer/Trutrac in back, & EEC-V MAF/SEFI
Reply | Threaded
Open this post in threaded view
|

Re: New fuel tank and sending unit weirdness (Questions)

Randy
I tested with the sender connected to the cable after I removed the sender from the tank, the meter goes E <> F in concert with moving the sender.  I also tested it using resistors across the cable contacts.  22 ohms (a number I found on one of your posts) puts it right at 1/2 tank. I also tested the sender with an ohm meter. Overkill, perhaps, to make up for my complacency when I installed it the first time. I plan to get back at it soon. The first step might be to find out just how much gas I do have in the tank. It's a bit harder now that I finished my Duraspark II conversion and gas mileage increased by 50%.
1984 F150, 300 Six, C5
Reply | Threaded
Open this post in threaded view
|

Re: New fuel tank and sending unit weirdness (Questions)

Randy
Would the tank ground influence the meter since the meter cable gets its return through the cable?
1984 F150, 300 Six, C5
Reply | Threaded
Open this post in threaded view
|

Re: New fuel tank and sending unit weirdness (Questions)

Gary Lewis
Administrator
The schematic below shows the senders grounding via ground G701, which is on the firewall behind the radio.  So I was wrong about checking the tank for being grounded as the ground comes through the cable.  Sorry.


Gary, AKA "Gary fellow": Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker in front & 10.25 Spicer/Trutrac in back, & EEC-V MAF/SEFI
Reply | Threaded
Open this post in threaded view
|

Re: New fuel tank and sending unit weirdness (Questions)

Steve83
In reply to this post by Randy
What do the battery terminals look like?

Walk softly and carry a BIG SIX!!!
https://www.supermotors.net/registry/2742#album
Memphis, TN, USA, Earth, Milky Way
Reply | Threaded
Open this post in threaded view
|

Re: New fuel tank and sending unit weirdness (Questions)

Randy
In reply to this post by Gary Lewis
Gary Lewis wrote
The schematic below shows the senders grounding via ground G701, which is on the firewall behind the radio.  So I was wrong about checking the tank for being grounded as the ground comes through the cable.  Sorry.
sorry? no need for that. Thanks for all the great stuff on this site.
1984 F150, 300 Six, C5
12