Fuel Tank/Fuel Gauge Issues with Passat

I recently purchased a 97 Passat TDI with 125k miles (to go along with my 01 Jetta TDI). I did the ventectomy-and fully vent the tank when filling. The fuel gauge doesn't go below the last white hash mark (last white mark BEFORE the red-reserve zone). Since my Jetta gauge goes all the way into the reserve-I expected that is what the Passat would do-but I actually RAN OUT of fuel (on a tank that had been fully vented) on my first full tank-because I thought I still had a couple of gallons left....when I filled up I put in 16.8 gallons....A friend who has a 96 Passat-just filled up with 18.7 gallons-and he doesn't even vent. I have heard estimates for the sedan for fuel tank capacity (fully vented) of between 19 and 20 gallons.....

Bottom line is I don't seem to be able to get the last couple of gallons out of my tank-AND the fuel gauge doesn't seem to be working at the low end of the fuel....

Anyone had similar issues and got some recommendations on how I could correct this??? It is reducing my range pretty significantly....fuel sender/tube perhaps??? Thanks....

The sedan capacity is indeed around 20 gallons fully vented. If you're only burning 17 gallons and the gauge is telling you that you're not empty, it may be telling you the truth.

I don't know exactly how the fuel pickup is configured in the tank, but it sounds as though the problem may lie there rather than your gauge.

My newly acquired B4 wagon also ran out while still indicating a gallon or two remained in the tank. I've presently repositioned the indicator needle to read 2 gallons lower than it did previously.
This is a temporary measure (pun) until I investigate the pick-up assembly in the tank. I may have a leak that allows air to be drawn in when the level drops closer to empty. Such a leak will effectively move the pick-up level higher in the tank and not permit fuel from lower than that level to be used.
When I have the time I'll park the car on a level surface and suck the tank "dry" through the fuel lines. That will be the same level at which the engine would be sucking air. This "empty" level, the level at which no more fuel can be moved to the engine, will be checked in comparison to the fuel intake. If the pick-up integrity is fine, I'll then add a premeasured five gallons of fuel and set the gauge to read four gallons.

I've presently repositioned the indicator needle to read 2 gallons lower than it did previously.

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Jon, how did you change the position of the needle in the gage cluster?

I too am having fuel gage issues when the tank is low. When taking sharp left turns, the needle plummets to 0 and returns once the car car is going straight again. I've had the sender out but found nothing out of order and everything was super-clean. It only acts up when there is little fuel in the tank, otherwise all gage readings are OK apart from inconsistent readings (changing all the time) when fuel is low (less than 4 gallons).

thx.

When taking sharp left turns, the needle plummets to 0 and returns once the car car is going straight again. I've had the sender out but found nothing out of order and everything was super-clean. It only acts up when there is little fuel in the tank, otherwise all gage readings are OK apart from inconsistent readings (changing all the time) when fuel is low (less than 4 gallons).

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I just recently had this problem and fixed it. You have to take the float arm off of its plastic pivot holder, then remove the holder. Clean the corrosion off of the copper surfaces of both contacts, i.e., the stationary "ring" and the portion of the "pointer" contact that has the 2 spring ears. One of the 2 spring ears didn't have much bend in it and allowed the float arm to have more lateral motion that it should, causing loss of electrical contact at the ring/pointer interface when cornering.

Chris, thanks. I'll go back in and check it. I did inspect the contact arm and it seemed to apply good pressure throughout the range of motion.

I'll hook the voltmeter up and verify resistance values...should have done this the first time around.

Any ideas for MichTDi on his "small" fuel tank?

There was a thread a few days back about Passats that are hard to start when the fuel guage gets low (like in the 2-3 gallon range).

I'm sure that these two topics are related.

I, too, would like to know how Jon adjusted his indicator.

WARNING for removing gauge needles. You may be able to remove the needle from its spindle without pulling apart the servo motor casing halves beneath the spindle, you may not. I've removed all the needles from several different B4 (TDI & GLX) clusters and only one or two of them came off cleanly. Its not a disaster if the casing halves separate, but be prepared for it. If it happens, see Section C-2 of my MFA article for instructions on how to repair it.

[/QUOTE] I too am having fuel gage issues when the tank is low. When taking sharp left turns, the needle plummets to 0 and returns once the car car is going straight again.

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I am having the opposite problem. When I fill it and vent for a full tank, the needle plummets to 0 on turns and returns once the car car is going straight again.

Where is the fuel sensor located and how do you remove it?

Chris, thanks. I'll go back in and check it. I did inspect the contact arm and it seemed to apply good pressure throughout the range of motion.

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There are 2 moveable contact points...the contact arm/resistor point and the point between the other end of the contact arm and the float arm holder pivot point. This second point was the problem.

Heh, mine has beeo doing the same thing lately, but I have been ignoring it.

Flip up the rear seat bottom and unbolt the access cover to get to the sending unit.

I am having the opposite problem. When I fill it and vent for a full tank, the needle plummets to 0 on turns and returns once the car car is going straight again.

Where is the fuel sensor located and how do you remove it?

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The remedy for this is the same regardless of where the "dropout" occurs. For me, it was w/ 1/4 tank remaining.

The fuel gauge sender is located under a large round sheet metal cover under the trunk mat on wagons.

I was freaking out the first time it happened since I thought I broke something. Now I just ignore it but I am going to try and fix it once the tanke get empty.

B4 Passat, not the A4 cars. The B4 have the sender access in the trunk or rear cargo area.

The needles can be repositioned without removal. The needles can be removed without risking pulling apart their drive gearbox.
Allow the needles to come to a rest on their stops with the ingition OFF. Continue to rotate the needles lower (CW on fuel, speedo and tach, CCW on water temperature). Twist and pull simultaneously applying more twist than pull. The twist will relieve the "stiction" and reduce the force needed to pull the pointer off the drive post.
Press straight down to reinstall. Twist only in the "lower" direction to align the pointer with the desired reference mark. If you twist it too far you'll have to continue another full rotation. Don't twist in the "increase" direction or the plastic drive gears may become damaged.

We had the same problem over the last couple of winters at even 4-6 gallons and in the warmer months when getting low as described. I also believe that the gauge is not lying, but rather you (and everyone else with this problem including us) has an air leak somewhere in the system.

The reason I say somewhere is because I don't think it to neccesarily be in the tank. This problem went away on our wagon when I replaced the injectors. A fuel leak on the #3 return also went away leading me to believe that was where the air was getting in.

What was happening in our car was air would recirculate between the injectors and the filter building up in the filter. Once there was too much air in the filter it wouldn't start or it would stall out and refuse to restart. It is my theory that when there is enough fuel (it would seem more than 2 or 3 gallons) there is enough force in the tank combined with the pump to overcome the air in the filter and get fuel to the engine. Once this level is dropped below there is no longer sufficient force to get fuel past the filter.

This seems to have been confirmed by the fact of filling the tank relieves the problem. BTW, the first time we had this problem it turned out that the O-ring on the filter was where the leak was coming from.

The needles can be repositioned without removal. The needles can be removed without risking pulling apart their drive gearbox.

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I don't recommend this. In my experience with several different clusters, the press fit of the needles varies greatly. With really tightly-fitted needles, in trying to rotate them to break them free, I've had a needle hub crack and another actually shear the needle right off the hub. Since then, I've been pulling them straight off the spindles with no damage to the needles no matter how tightly installed.

Having said that, though, it is a lot less work to reposition or remove a lightly-pressed needle that doesn't take the servo motor casing with it when it comes off. So, if you are just repositioning the needle, you can try, with very low torque, to rotate it when at its lower stop. But I mean really low torque, and if it doesn't break free under these conditions...STOP and pull it straight up and off before you break it. If you're doing an MFA conversion, you'll have an extra set of needles in case of breakage, but if you're just reindexing the needles without a spare cluster around, use extreme caution (and very little muscle)...cluster parts are not available.

so we're going hiking this last Saturday and I go to start the car (wagon) and perhaps I'm too quick with the switch or whatever, the car starts fine, but the tach is grinding (yes noise) away against its stop. So I wait, it stops but stays at zero. So I shut it off and restart and its fine, but now the fuel gauge is sooooooo full (the tank had about 16-17 gallons in it) that the needle is resting on the hub of the temp gauge needle.

As I drive, it slowly lowers itself. The closest I got was a (proportional) reading of about 24 gallons. A reset would cause it to go all the way back to temperature land. After hiking we meandered our way back home through the mountain valleys even stopping at a grass air strip who's hanger was full of old planes and parts, very coool but I digress. The point is it was started and stopped a number of times, but it never went away. Later in the day it did start more or less straight up as opposed to clear left, but never anything approaching normal.

Yesterday we drove the beetle everywhere (BTW, Bourne Supremecy is a rental if you haven't already guessed from the commercials) and today I get in and start the wagon and it goes directly to about 12 gallons which is about right given the driving we did Saturday.

I'll of course keep an eye on it, but any ideas for the cause of this?

Has anyone got this figured out yet??? I haven't pulled my sending unit yet to have a look (hopeful that one of you would do it first-and give some information on what the problem was).

The air leak theory sounds like a good one to me.....

I thought about buying a new sending unit-but its like $109 from Impex-but if it is just a hole-perhaps it could be patched somehow......I'd rather have a "free" fix than a $109 one if possible......Anybody figure it out yet???

The problem is the sender and here is the fix.

Thanks Chris-but I think that my problem is different-the gauge is fine-I just don't have "access" to the last two to three gallons in the tank for some reason.....perhaps there is a hole somewhere such that after the fuel gets down to a certain level in the tank-the hole is exposed-thus no suction of fuel after that point......I have never used biodiesel (perhaps the previous owner did). My gauge will not go down into the "reserve" area......the fuel is really still there (2 or 3 gallons) as the gauge is showing-but evidently suction is gone-and then the engine dies for lack of fuel (as if its empty).......

I'd just like to be able to get at that last 2-3 gallons-because the fact that I can't seriously reduces my range/time between fill-ups......

Oops, there were a couple of different problems mentioned in this thread...I guessed the wrong one.

If you're only missing the last 2 or 3 gals., the problem may be a partially plugged pickup screen. The screen is vertical and is about an inch tall. The flex hose is mounted much higher up and, if sucking air, would probably result in more than 2 or 3 gals being unavailable.

I know that with my '97 Passat my fuel gauge sometimes acts up. It will read a little low, sometimes for a few minutes, and occasionally will even drop to zero. It is very rare when this happens and I don't think I have seen it happen in six months. One of these days I'll have to fix it.

As for the "empty" position, where the needle sits with the ignition off is it's stop. When you turn the ignition on the needle is driven into the stop position (this causes a buzzing noise. Normally you cannot hear it). The drive system is a stepper motor and a couple of gears. The motor doesn't have enough torque to harm anything, so when the gauge is done "zero"ing itself out it moves to its indicated position. So, if you want zero to read different from what you have, you will have to make sure you load the needle toward the stop, as mentioned in one of the other posts.
When I adjusted the needles on my car I could not pull them off, no matter what I did. Spinning them on their posts was not a problem.

As for fuel level, I will have to check the pickup on mine as well. When I fill the tank without venting the needle goes up above the 18gal. mark. If I vent it goes to the same place, so it seems like I am maxing the upper limit out. When I run the level down to the point that the engine will start starving for fuel I am down at the lower red hashmark. From that point, venting and letting the foam settle out I still could not put 19 gallons in the tank and the fuel was up 1/4" from overflowing the filler.

Mine won't even go down into the reserve area (red hash marks)-and I "ran out" (well the engine was starved for fuel anyway) and proceded to put 17 gallons in (and the tank was fully vented). So-I think that my guage is accurate-and I do indeed have 2+ gallons left-but because of a hole-or partially clogged screen in the pickup tube-cannot get to the last couple of gallons......I am gonna try to check it out this weekend.....

I have shortened the float arm by increasing it's angle to restore the linearity of fuel measurement. It now reads at the lowest mark when it sucks air. Some fuel remains in the tank at this level.
Bending the float arm more acutely made five additional gallons plus the "empty" volume read 4 gallons. Another five gallons brings the indicator up to between 8 and 10 indicated. This low level accuracy is of more concern to me than the full accuracy.
Yet another five gallons added is indicated as 14. Another five gallons is just above the 18 gallon "full" mark. Another five gallons on top of all that fills almost into the neck and keeps the needle pegged above 18 for almost 300 miles.
Nice that the accuracy is retained with full tank measurement too.

I have the same problem. My fuel gage started to zero out while in the middle of driving and would come back to 6 to 8 gal mark. I will try the remedy of cleaning the fuel transmitter contact. I hope it works. If it does not, then I will just log how many miles I drive and make sure to refill before going above 700miles.

I am having a similar problem of the car not getting fuel, but fuel still left in my tank. I have vegetable oil in my main 18. ? tank and I have diesel in a 5gallon tank mounted behind oem tank. my diesel tank will completely empty, so this would seem to leed me to think our problems are connected and they are sender related. Although I am still not ruling out, a leaky injector heat shield or something.

I have been having blown fuel lines, which I just realised is due to a one way valve in the fuel supply line, I think I remember that little plastic valve in line by the tank, I guess in other models that valve is in the sender unit and they drill it out. I have to yank that valve today anyway so while I'm in there I'll see if my pickup is clogged.

Well yanked the valve, total PITA. Now I can send my fuel in both directions. Checked out the fuel sender unit. No real clogging on the screen no visibal corrosion on my sender (remember i am running SVO not biodiesel). I think my heater just isn't low enough to work when I only have 4 gallons left in my tank.

I have finally gotten around to pulling the sending unit and trying to figure out why I can't access the last 2-3 gallons of fuel-and why my fuel gauge won't go down into the "reserve" (red hash marked) area. There wasn't any "crud" plugging the screen-and the unit seemed to be operating fine. Perhaps the spring loaded mechanism is not allowing the intake to COMPLETELY rest on the bottom of the tank-that is one possibilty (although that doesn't seem to be the case).....related to that is that the metal pickup tube (inside the plastic sending unit) perhaps doesn't go quite as far down as it should........the only other thing I can think of-is that perhaps the tank has shifted slightly and the sender isn't sitting (on the bottom of the tank) at one of the lower spots anymore (I don't think this is likely-I am kinda grasping at straws at this point)!!!!

A friend has a 96 (mines a 97) both B4's......and his is working fine-AND goes into the reserve-and he routinely fills up with 18-19+ gallons).......we are planning on SWAPPING sending units......which will at least tell me whether my problem is with the sending unit itself......or somewhere else........so this is just an update.....

Hmmm... ran out of fuel this morning so did a search on fuel guage. Similar situation... guage showing around 2 gallons left when the engine sputtered and stopped. Only 2 miles from home so not too bad a walk. Trip odometer suggested I still had 100 to 200 miles to go before I was in trouble and the low fuel light never came on. When I filled it, it took almost 24 gallons vented (it's a wagon) so seems that the tank might really have been empty? And, yeah, the mileage had dropped from 44 to 34 for some reason hence the diminished range. I'll add this to my long "to do" list but in the meantime, I won't let it get that low again! Any additional thoughts as to what might be causing this to happen are most welcome!