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Topic: Gas tank won't fill to full. (Read 14706 times) previous topic - next topic

Gas tank won't fill to full.

I’m trying to figure out why the tank in my Thunderbird won’t fill up to full. It has started the last two times I’ve added gas to the tank and it has occurred at two separate stations. What happens is that the gas nozzle clicks off before the tank is full, at least according to the gas gauge, which says the car has 18 gallons of gas instead of “F” (full digital cluster). If I try to add any more gas the pump keeps shutting off and a little bit of gas will come out the filler neck (perhaps even around the O ring where it joins the tank). I figure it’s either one of two problems:

1.The gas gauge is off and the tank really is full.

2.The filler neck to inlet pipe to gas tank O ring needs to be changed.

3.There is a problem with the filler neck.

Thoughts? I’m leaning more towards problem 1 or 2 myself.
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

Gas tank won't fill to full.

Reply #1 –
Seems like the gas pumps are more sensitive and shutting off sooner.  It sounds like when you add extra gas, it is already actually full.

I would guess the sender isnt reading all the way full.  I wouldnt drop the tank for it, if it were me.
Mike

Gas tank won't fill to full.

Reply #2 –
I had another thought: perhaps the vent line is plugged or bent? I'll have to take a look and see. I'm hoping it's that vs. dropping the tank to get at the sender. That's no fun. I've done it before with a quarter tank of gas to change the fuel pump. It's got at least three quarters of a tank in it right now....
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

Gas tank won't fill to full.

Reply #3 –
try a diff gas station before you go hunting for blockages, or drop the tank
[SIGPIC][/SIGPIC]
***** Project "EVOLUTION" 1987 Cougar LS  & 1985 Cougar Convertible *****
[/COLOR]
5.0 HO 306 roller block, machined GT-40P heads, Wiseco dished forged pistons, Eagle forged floating I-beam connecting rods, Lunati pushrods, ARP bolts, Scorpion aluminum 1.6 rockers, Comp Cams Magnum 266HR, Explorer intake, 65mm TB, MAF Conversion, 19# injectors, Ford Racing stainless P-headers, 2-1/2" cat-less exhaust w/ Flowtech Afterburner lers , SC AOD with 2800 BDR torque converter, 3.73 T-Lok rear, CHE rear control arms, full 2-1/2" frame w/1" jacking rails & seat supports, Rear disk brakes, Turbine wheels, All original interior w/ floor shift upgrade .......
Pretty much every panel on my 87 is new, rebuilt, or re constructed. :D
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Gas tank won't fill to full.

Reply #4 –
Quote from: daminc;422454
try a diff gas station before you go hunting for blockages, or drop the tank

X2. I had that issue. It was the pumps at that particular station.
'88 Sport--T-5,MGW shifter,Trick Flow R intake,Ed Curtis cam,Trick Flow heads,Scorpion rockers,75mm Accufab t-body,3G,mini starter,Taurus fan,BBK long tube headers,O/R H-Pipe, Flowamaster Super 44's, deep and deeper Cobra R wheels, Mass Air and 24's,8.8 with 3.73's,140 mph speedo,Mach 1 chin spoiler,SN-95 springs,CHE control arms,aluminum drive shaft and a lot more..

Gas tank won't fill to full.

Reply #5 –
Quote from: daminc;422454
try a diff gas station before you go hunting for blockages, or drop the tank

It can't be the pumps. It's done it at three different gas stations.
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

Gas tank won't fill to full.

Reply #6 –
My 88 TC is very sensitive to angle of car when filling the tank.  If it is pointed slightly down hill, I can get 2-3 gallons more in it than if it is level or pointing up hill.  I figured it was just the shape of the tank and perhaps an air bubble trapped in the top of the tank that doesn't "burp" out unless the car is aimed down hill.

Another tip... when you top off, pull the nozzle out some so the air vent (the air vent part way up the nozzle holds a suction tube, which is what triggers the shut-off when it starts pulling fuel rather than air) doesn't keep sucking up the fuel you just added.  While leaving the nozzle in the filler neck, but above the gas level, reach over to push the gas pump shutoff (usually the little flap that is pushed up when you return the gas nozzle to the pump).  Squeeze the nozzle handle to release the gas pressure in the nozzle head and you may get a half cup or so more of fuel.  This will minimize drips and will give you some fuel you paid for (or the person ahead of you paid for) but never collected.  This may also have been the fuel that was sucked up into the suction tube to trigger the shut off.  Over time, this can add up.  $3.20 / gallon = 20 cents per cup.

Gas tank won't fill to full.

Reply #7 –
since you have s full digi dash, im betting you have exceptional highway gas mileage.

im betting the sender or wiring to sender has some additional resistance.,, sender or wiring kina messed up somewhere.

jumper your tan/light green wire at the self test connector to ground then turn the key forward.... then disconnect the fuel supply line and prep it to dump fuel into a couple gas cans.

turn your key forward to empty the tank.... thats what we did on my sons bird to get the fuel pump changed.

Gas tank won't fill to full.

Reply #8 –
I'll be ed if you just didnt jinkx me.  Mine just did the exact same thing. 

That is the first time its happened. The gauge said 3 gallons left.  I filled it up and it shuts off at 15 gallons.  I figured it just clicked early and tried to add more, NO DICE, tank was full.

Started the car and it reads 18 gallons.  I instantly thought of you and this thread.  WTF!!!!!
Mike

Gas tank won't fill to full.

Reply #9 –
So yours reads 18 gallons and if you try to add any gas it overflows? Sounds like mine :hick:. I haven't looked into it yet as I haven't had a chance to see what's up. I may not be looking at it till the spring. Being that the car is getting put away for the winter in about 5 weeks I may just drive it as is and figure it out in the spring. I'm betting it has something to do with the float/sender in the tank. I don't think the part is available, which could make fixing the issue fun.
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

Gas tank won't fill to full.

Reply #10 –
Quote from: jcassity;422659
since you have s full digi dash, im betting you have exceptional highway gas mileage.

im betting the sender or wiring to sender has some additional resistance.,, sender or wiring kina messed up somewhere.

jumper your tan/light green wire at the self test connector to ground then turn the key forward.... then disconnect the fuel supply line and prep it to dump fuel into a couple gas cans.

turn your key forward to empty the tank.... thats what we did on my sons bird to get the fuel pump changed.

Is it possible to probe the wires somewhere without dropping the tank?
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

Gas tank won't fill to full.

Reply #11 –
the wires go through the trunk
[SIGPIC][/SIGPIC]
***** Project "EVOLUTION" 1987 Cougar LS  & 1985 Cougar Convertible *****
[/COLOR]
5.0 HO 306 roller block, machined GT-40P heads, Wiseco dished forged pistons, Eagle forged floating I-beam connecting rods, Lunati pushrods, ARP bolts, Scorpion aluminum 1.6 rockers, Comp Cams Magnum 266HR, Explorer intake, 65mm TB, MAF Conversion, 19# injectors, Ford Racing stainless P-headers, 2-1/2" cat-less exhaust w/ Flowtech Afterburner lers , SC AOD with 2800 BDR torque converter, 3.73 T-Lok rear, CHE rear control arms, full 2-1/2" frame w/1" jacking rails & seat supports, Rear disk brakes, Turbine wheels, All original interior w/ floor shift upgrade .......
Pretty much every panel on my 87 is new, rebuilt, or re constructed. :D
Join us on Facebook
http://www.facebook.com/home.php?sk=group_137541156293768&ap=1

Gas tank won't fill to full.

Reply #12 –
Quote from: thunderjet302;422691
So yours reads 18 gallons and if you try to add any gas it overflows? Sounds like mine :hick:. I haven't looked into it yet as I haven't had a chance to see what's up. I may not be looking at it till the spring. Being that the car is getting put away for the winter in about 5 weeks I may just drive it as is and figure it out in the spring. I'm betting it has something to do with the float/sender in the tank. I don't think the part is available, which could make fixing the issue fun.


Exact same reading (18 gallons), just like you.  I probably wont mess with it.  I had my tank down and sender out about 2 yrs ago while installing my Walbro 190 pump.  Everything worked fine till yesterday??????
Mike

Gas tank won't fill to full.

Reply #13 –
I hesitate to throw this information into the thread, BUT...  Last year I discovered the IVR (Instrument Voltage Regulator) was responsible for problems I was having with the Temp Gauge and Fuel gauge.  The fuel gauge on the 88 was always quirky from new.  The needle would always be beyond the full line on fill up.  While the gauge was not inaccurate at low fuel, it did have wide mood swings in operation--just making it quirky.  The adjustment of the IVR solved this and the temp gauge issue.  About 8 years ago, the temp gauge needle began running hot.  I ended up chasing down all the other reasons for this before discovering the nasty IVR a year ago.  It is one nasty little piece of work. 2 Pic attached.  It is mounted on the back side of the dashboard gauges (instrument panel).  I toyed with IVR adjustment, and you would be surprised what this tiny thing can do to the 2 gauge needles (Temp and fuel) it controls---see sample pic of wacko gauges when I started playing with it.

Gas tank won't fill to full.

Reply #14 –
No dice in this case it's a full digital – so the IVR is for all discussions out of the picture in my opinion

The doctor however has taken apart and fiddled with a couple of floats and I have a link to an older discussion about using standard floats in converting them to full digital cluster variable resistor floats

On a sidenote I find it very interesting that two separate people have to identical problems geographically located into separate parts of the world

Seems to me like if the odds of the floats being the problem now has Decreased

If one person complained about their tank not showing a full reading and as was described then of course I would want to jump on the wiring passing through the trunk to take a resistance rating
Now that a second person has the identical symptom the odds of both of them only being able to display 18 gallons's is starting to point me toward something about the fuel computer or computation system

The odds of two people having the identical problem and arriving at the same numerical value is very slim if we point to the float as probable fault

With this new variable in the mix I have no idea where to start now
Before I was thinking about having him measure the float by grabbing the wiring passing through the trunk and isolating the float

I'm open to other ideas and I think the float might be something we should ignore for now
This thread is going and up yeilding a lot of good information I believe so let's keep talking