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.
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.
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....
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.
It can't be the pumps. It's done it at three different gas stations.
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.
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.
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!!!!!
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.
Is it possible to probe the wires somewhere without dropping the tank?
the wires go through the trunk
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??????
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.
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
Thunder jet
Like the doctor said the wires pass through the trunk however you should try to figure out a way to make the level of the fuel change so that you can take a couple or three or even four readings by resistance
I suppose there might be a connector in the trunk but I'm not sure
Most definitely we need to isolate the float if you want to go that route and this is why I recommended you use the test connector to make the fuel pump run continuously you can empty it out and then add some fuel back and measure the resistance of the float and then add a little more fuel back in measure the resistance of the float so on and so forth
Does Kansas use a "winter" and "summer" gas blend like Illinois? Perhaps this has something to do with the ethanol content of the gas?
On a side note my Mark VII does something similar. The gas pump clicks off but the needle on the gas gauge isn't at the full line. It's slightly below it. Perhaps the ethanol in the gas screws with older floats?
I would hate to think that our floats are starting to get full of liquid making them heavier but I suppose it could be an option
Both of your floats yours and his would've had to of taken on the exact same amount of fluid though
Once upon a time a lawnmower carburetor float started to take on a little bit of gas and made it run incorrect until I Soldered it and fixed the problem
Mine clicks off and shows 18 or 19 most of the time. It didn't used to, but earlier this year when I switched cars and did a transplant marathon, I moved the tank to the other car (it has my Walbro 190 and there was no problems with it except that it needed a new filler grommet) and lowered it, which radically changed the stance. My variables: Tank swapped but not opened, lowered - possibly changed resting angles of the tank, and replaced the filler grommet.
Sort of off subject, has anybody figured out how to stop fuel sloshing away from the pickup on hard left/left drift? Doesn't do it to the right at any fuel level, just to the left with 8 gallons or less.
If I stand on the throttle from a stop in my Thunderbird with about 1/2 tank or less of gas the car stalls as all the fuel sloshes away from the pump pickup :hick:.
AFAIK, the Kansas fuel is the same year round. I think Kansas limits it to 10-15% Max.
If the fuel was changing, I would think I would have noticed this before, Ive had the car here for 6 years.
Im confused?
Here are the test procedures to enter the diagnostic mode and then troubleshoot a inaccurate fuel reading
Here they are
full digi clusters require a sender that reads low resistance when empty, high resistance when full
clusters that are buttstuffog or only have an electronic speedo are opposite resistance readings.
a snipit from my diy link below....................................
==============================================
Fuel sending unit info
Conventional "buttstuffog cluster"
87 Evtm page 127 or 129 shows
Empty - resistance - 60 to 86 ohms
Full - resistance - 8 to 12 ohms
Fully Electronic cluster
87 shop manual 33-05-23 troubleshooting step TJ6 shows
Empty- resistance-9-12ohms
Full-high resistance - 154-160ohms
88 turbo was able to verify his fuel guage was working properly. Just unplug the gray two wire connector "C491" under the package shelf accessable in the trunk. The two wires are yellow/white and a black. Insert a 10 ohm resistor in tehplug crossing the yellow/white and black wire. Make sure you have jumpered the fuel guage side of the wiring harness with this 10ohm resistor. Turn on your key and the needle should peg showing a full tank. This test was performed on a thunderbird turbo version. I wouldnt think it would be different for 3.8 or 5.0 engines but one never knows.
lay on your back under the tank
look to the right
find a two wire harness
one wire is yellow / white
the other is likely black.
this should be the sender harness
grab harness and follow its path up
it should be going up and finally under your package shelf in the trunk
package shelf-in trunk up near speakers
get in trunk
look for a connector with yellow white wire and a black
unhook connector
one end goes to your dash guage
the other goes to the sender
disconnect sender connector
connect red meter lead to the yellow white
connect black meter lead directly to the metal tank***
do not deviate from the above two steps or reading may be wrong
set meter to resistance and read
jot down that number you get
add 5gal of gas
read sender
jot down that number
if there is a change then the sender is assumed to be good.
To test the guage, insert a paper clip in the connector (C491)
This connector is the other end you disconnected leading to the guage
turn on key
gas needle will peg if its good
gas needle will peg if its a conventional cluster
gas needle will go to empty if its a digital cluster sender
go to my diy link below for details.
go to my electrical tech sticky "1987 evtm" page 129 for wiring diagram.
post your results
You can define what sender you have based on your readings as well as determin if it works.
I have often thought that if one puts a digital cluster sender in a conventional dash car, the leads on the guage can be flipped there to compensate for the tank circuit,,,,,,,,,,(you getting this daminc?)
This is going to give me something to do over the winter while the car is in storage. Thanks! :)
so I was driving to work today. stop at a light and my temperature is pegged!
but when I left for work, I also had half a tank of gas...
(http://i33.photobucket.com/albums/d82/bosenKevin_02/2013-10-04093310.jpg)
ignore the 80mph... my speedo reads too fast dues to the 99+ mustang trans.
(http://i33.photobucket.com/albums/d82/bosenKevin_02/2013-10-04094201.jpg)
this is after cycling the key on and off and waiting for all gauges to stop moving immediately after parking the car.
I'm starting to think my car wasn't overheating after all.... I always shut it down before it got into the read previously.
Check your IVR. I think it may be causing the pegged-gauge issue...
How the hell is it reading 84 MPH in park?
The indicator is clearly broken.
haystack,
you want 5v coming out of the ivr,,, thats the goal.
there is also a resistance wire off the ignition switch which is a thin solid conductor approx 18awg that leads up to your instrument cluster.
you will find this thin wire on the plug in on your igntion swtich parallel with a larger gray/yellow wire.
my sons full ananlog cluster had unreliable guages and i found this little gray wire connection at the spade connector to be broken. the insulation was holding the wire in place.
people who take the column covers off and on bend up thier wires and this one particular wire is a single solid conductor.
it will have 12v going into it but on the other end up at the cluster, it will be lower , not like the evtm says but low enough around 5 to 7v.
next would be the ivr.
thanks Scott, I will check this when I get around to it.
about the dash reading 84 mph, that is just a touch under 25 mph. swapping a 99-04 t-5, the oss, which plus right into the vss, reads speed, traction control, and abs. the mustang computer splits these signals up, where our cars don't.
so dash reads about 4 times as high, until I can get around to finding a 94-98 transmission which used the same setup our cars did, and swap the tail shaft.
Well I went to the gas station today and filled the Thunderbird up (one of the 3 stations I usually stop at). The gauge said 10 gallons were in the tank. The pump said it took 12 to fill up (10+12=22 the tank capacity). I turned on the car and the gauge said F. So now the stupid thing wants to work right again. Instead of saying 18 when the tank is full the gauge has randomly decided to go back to displaying F :wtf:.
sounds like the same thing climate control does sometimes... the symptoms come and they go.
these are probably examples of the problems that came in the door at the dealership then went back out the door unresolved all the time.
there's no real way to troubleshoot these fickle or intermittant issues when there is no real clear way of simulating or introducing a fault when we dont clearly understand where the source of the fault might be.
oh wel... atleast now you can pull the codes off your cluster.
I'm going to pull codes from the cluster as perhaps it is still at fault. It a random problem like this that comes and goes that drives a person nuts. The only thing I can think of is that it *could* be a grounding issue. I know Mark VIIs built before 1990 are pr0ne to having faulty gas gauge readings. The fix is to install a ground strap between the tank and frame of the car. I might try that with my Thunderbird and see if it makes a difference. It's cheap and worth a shot.
i wonder what safety bullet items there are to list since the oem tank did not have a chassis ground.
for instance,,,,
welding on the frame...........
you are injecting a voltage throughout the frame of the car,,, the welder has a ground clamp.
at some point the gas tank ground strap becomes resistive due to corrosion or just age...
could that not introduce a voltage drop and current flow to ignite fumes?
this is an interesting comment you have made,, and not haveing a ground strap oem is probably engineered for a reason.
dono... chime in all you ASE guys!!!!
i wonder what safety bullet items there are to list since the oem tank did not have a chassis ground.
for instance,,,,
welding on the frame...........
you are injecting a voltage throughout the frame of the car,,, the welder has a ground clamp.
at some point the gas tank ground strap becomes resistive due to corrosion or just age...
could that not introduce a voltage drop and current flow to ignite fumes?
this is an interesting comment you have made,, and not haveing a ground strap oem is probably engineered for a reason.
dono... chime in all you ASE guys!!!!
on the flip side,, in my work world,,,
we have to bond diesel fuel tanks of generators to the exterior ground ring by way of cad welds... so,, it must be ok to "chassis" earth ground a fuel tank wihtout any worries of what i said in my earlier post....
on the flip side,, in my work world,,,
we have to bond diesel fuel tanks of generators to the exterior ground ring by way of cad welds... so,, it must be ok to "chassis" earth ground a fuel tank wihtout any worries of what i said in my earlier post....
I know the tank on my car has a plastic shield under it. The tank straps never touch the actual metal tank but instead the plastic shield. I have to assume that the sender is grounded not through the tank (since it is insulated) but instead through the wiring harness.
The 84-89 Mark VIIs that have issues with the fuel gauge don’t have a little ground strap running from the tank to the chassis. Ford fixed the problem on the 90-92 Mark VIIs by adding that little ground strap from the factory. I’m wondering if doing the same thing on a Fox Thunderbird/Cougar would fix the problem?
Holy thread revival!
I fixed the problem early this spring and forgot to post the solution. It turns out that somehow the fuel filler neck and slipped lower into the tank than it should be. The plastic shield it sits in cracked and the neck in turn sank. since it sat lower fuel was getting pushed up the neck before the tank was full. I pulled the neck up to the correct height and repaired the plastic shield the neck mounts to behind the fuel door. Vola the tank now take up to 22 gallons and the dash says it's full. It ended up being a mechanical rather than electrical fault after all.
Mine went on a tantrum a few weeks back and kept saying more gas and miles till empty after I had driven it 15 miles and not added any gas. Did it 3 days straight, then stopped.... I'm not even gonna start to mess with any of it until the issue stays. It's reading correctly as of right now....
How full was the tank? It takes quite awhile for the gauge in my Thunderbird to come off F. F is 22 gallons. The next number below F is 20 so it will take a good 30+ miles of "normal" driving to get it to come down.
That's awesome! Does anybody know how to make the fuel pump not suck air on a hard left?
Or in my Thunderbird's case not suck air with less then 1/2 tank and a full throttle launch and/or passing maneuver? The car rears up so hard that gas sloshes away from the pickup :hick:.
Lou, I have an extra black plastic part you're talking about. If you want it, it's yours.
I had 6 gallons I think. Next morning it read 9. Day after read 7. Should have read 4 by that point. Put $30 in and it stopped. I've run it that low since without issue.
Thanks for the offer. I managed to JB Weld mine back together. I did it from the back. Looks just like stock.
If I run mine below 7 gallons it will sometimes go to E and slowly climb back up to 7. I think it's a float/sender issue.
I wonder if that could be the issue with my TC. Depending on how the car is parked tilted one way or the other, depends on how full the tank gets and how the gauge reads when I'm done. Doesn't read clear full all the time. But I have a regular type gauge, not the digital one. I think I'll check that filler neck here when I get a chance. Good thread to read.
The best way is to either SUMP the tank and install a rail pump and or mount the pump horizontal to the bottom. problem fixed.
Eventually I will do that. For now I just keep the tank above 1/2 full till I get around to it.
I know Im a little late here, but mine did the same thing. The gas pump shut off at 17gallons. I have a 21gallon tank. I tried filling it up again. Nothing. about a week later, filled up at a different station, never happened again. weird.
And regarding your instrument cluster, my dads friend worked a ford dealership and he said the clusters go bad every now and then. Mine had a issue where the speedo didnt show anything. Just blank. Didnt even read 0mph. Blank.
Needless to say, I got a new cluster. No problems since.
And important side note, if you have a full digital cluster, your odometer reading is stored IN the cluster so if you swap clusters, your odo is way off. And you have to do maths to calc your actual mileage.
Oh, and I know the digital odometers roll over at 200K miles....the go from 199,999.9 Miles to 100,000.0 miles
I had to replace a tank in another car and noticed there was no conductive path from the filler tube to the car or any other part of it. The filler was surrounded by rubber where it entered the tank on one end and the other end bolted to a large plastic shroud type thing. There was no ground strap or anything I could find that would allow any electrical difference of potential (static charge) between the filler tube and the rest of the car to safely neutralize. Am I misunderstanding something here?
It's not a Cougar or TBird so I didn't think this question qualified for its own thread.
Believe it or not the fill pipe that is rubber contains carbon that conducts electricity fairly well. I once played a joke on a state inspector at an emission seminar in Ct. He was demonstrating how NOX can be easily repaired. He broke for a break and me and John stayed in the shop alone. So i cut a piece of 1/4 inch vacuum hose and replaced it with the coil center wire. Thinking the car would not run and drive this inspector nuts. Well the car started perfectly and ran just fine. I confessed doing it as a joke and we were all shocked that the car ran and ran perfectly. The reason was the hose was loaded with carbon that conducts. So we were told that those filler hoses are in fact conductive and do not need to be grounded. This seems like it's true as many cars we service do not have ground straps any more. have a good weekend guys.