Fuel Tank Failure
05-14-2018, 05:05 PM
#1
AudiWorld Senior Member
Thread Starter
Fuel Tank Failure
I've been having issues with my S8 not running below half a tank of gas. I had my Audi dealer replace the fuel pump assembly, as they diagnosed a pump failure, and still had issues. The tech double checked everything and even replaced the newly installed fuel pump assembly but the issue continued.
Well after some exploring by several Audi techs, they found out the tube that pulls gas from the secondary part of the tank had gone bad/had a crack in it. Because of the crack, when gas got bellow 1/2 a tank, the pump would suck in air, not gas. The techs said this was an issue with the D2. However, I've never read or heard of this before. Has anybody ever experienced or heard of this before?
Well after some exploring by several Audi techs, they found out the tube that pulls gas from the secondary part of the tank had gone bad/had a crack in it. Because of the crack, when gas got bellow 1/2 a tank, the pump would suck in air, not gas. The techs said this was an issue with the D2. However, I've never read or heard of this before. Has anybody ever experienced or heard of this before?
05-15-2018, 07:22 AM
#2
No. Never in 13 years. Any evidence of rock or jack damage to the tank?
I recall some magazine writer saying Porsche 928s had a problem with cracked blocks and some bozo I was selling a 944 Turbo motor to said they had a problem with frequently cracked pistons and cracked compression rings. I never heard of that stuff either.
I recall some magazine writer saying Porsche 928s had a problem with cracked blocks and some bozo I was selling a 944 Turbo motor to said they had a problem with frequently cracked pistons and cracked compression rings. I never heard of that stuff either.
05-15-2018, 11:53 AM
#3
AudiWorld Senior Member
Thread Starter
Nope. The Audi tech said the tank was undamaged. The bill they quoted was for $2600 for parts (new tank, as the needed hose is no longer available) and labor. My next step is to get a borescope and look in the tank for myself.
05-15-2018, 03:56 PM
#4
AudiWorld Senior Member
Total Horse****. The pump is not at the lowest point in the tank. It sits in a cup assembly inside the tank. Once the fuel level falls below the top edge of the cup, the pump gets fuel in two stages. First, it siphons fuel from a series of accordion tubes way down low in the nether regions at the bottom of the tank. These siphon hoses are attached to and continuously fill the cup, and then the fuel pump pumps the fuel from the cup to the engine.
The fuel pump assembly has a small plastic male tube about the thickness of your pinky finger pointing straight down that needs to mate with the female port on the side of the cup inside the tank. The cup inside the tank is free to move around a little bit. Accordion hoses are clipped to the floor of the tank and feed the cup. These hoses reach out like octopus tentacles to the far front left and right of the saddlebag tank. If the suction probe on the side of the fuel pump plastic housing misses the suction port inside the tank, then the tentacles don't suck fuel from the low points to fill the cup in which the fuel pump is submerged. The symptom is the car "runs out of gas" with the tank half full...give or take.
You can bolt in the pump using the foot long bolt and still have misalignment of the ports. THIS IS THE COMMON PROBLEM. The fix is to partially remove the pump assembly. Disconnect the wiring and the lines. Undo the big black ring, back the bolt out half an inch then give it a rap on the head to push the internal cup down to separate the pump from the cup. Now completely undo the bolt and remove it, remove the integrated fuel pump sender, and raise the pump assembly out. At this point you could attempt to reinstall the pump correctly. The trick is to rotate it in clockwise while holding it up as much as you can until the arrows are aligned, then gently push it straight down. Think of it as you are turning in a screw but instead of pushing down, you are holding it up slightly as it progresses down. Only let it down enough to rotate clockwise If you push it down too soon, the male suction port ends up next to rather than inside the corresponding female suction port inside the tank. Like prom night all over again.
If you are CERTAIN the ports are mated correctly, another common issue is one of the accordion hoses inside the tank has popped loose from the cup inside the tank. How did that happen? Well if someone tried to pull the whole assembly out without using the partially loosened bolt to push the cup down, then the cup gets pulled up and a hose can pop loose. Simple to reattach. The accordion hoses have two teeth on opposite sides. squeeze the connection perpendicular to these teeth and the hose pops free Squeeze the teeth toward each other with a pair of pliers to tighten the hose, snap it back on and that should work. These hose ends look like the plastic PCV hoses used in my now departed B7 A4.
To test that you got it right, remove the banjo bolt at the top of the pump assembly. find a threaded hose barb that matches the thread. Thread it in. Attach a length of cheap fuel hose to feed into a five gallon gas can. Remove the passenger' side front carpet. Open the relay box. Slide out the tray with the fuel pump relay. Pop the plastic cover off the FP relay. Wedge the relay contacts closed with a folded matchbook cover or thin piece of vinyl tube. Gently now. Turn the key to RUN, and the pump will run continuously. Pump out the tank into the gas can. Switch off, swap cans and keep pumping. When you can pump out the entire tank, you got it right. The Audi approved method for checking is drive it around and hope the engine doesn't quit. Idiots.
I actually had to make a "special tool" ...foot long hole saw... to remove my pump when the captive nut inside the tank broke loose. I drained the tank, filled it with a garden hose, cut out the assembly, shop vac'd the water, reached into the tank with a magnet to collect any filings, shop towels to the farthest recesses, took the cup out entirely, epoxied the nut, reattached all the inner hoses, new pump and assembly..10 years ago. No problems.
They probably just misaligned the pump on installation. Absent that, there is a loose accordion hose inside the tank where it attaches to the cup.
The fuel pump assembly has a small plastic male tube about the thickness of your pinky finger pointing straight down that needs to mate with the female port on the side of the cup inside the tank. The cup inside the tank is free to move around a little bit. Accordion hoses are clipped to the floor of the tank and feed the cup. These hoses reach out like octopus tentacles to the far front left and right of the saddlebag tank. If the suction probe on the side of the fuel pump plastic housing misses the suction port inside the tank, then the tentacles don't suck fuel from the low points to fill the cup in which the fuel pump is submerged. The symptom is the car "runs out of gas" with the tank half full...give or take.
You can bolt in the pump using the foot long bolt and still have misalignment of the ports. THIS IS THE COMMON PROBLEM. The fix is to partially remove the pump assembly. Disconnect the wiring and the lines. Undo the big black ring, back the bolt out half an inch then give it a rap on the head to push the internal cup down to separate the pump from the cup. Now completely undo the bolt and remove it, remove the integrated fuel pump sender, and raise the pump assembly out. At this point you could attempt to reinstall the pump correctly. The trick is to rotate it in clockwise while holding it up as much as you can until the arrows are aligned, then gently push it straight down. Think of it as you are turning in a screw but instead of pushing down, you are holding it up slightly as it progresses down. Only let it down enough to rotate clockwise If you push it down too soon, the male suction port ends up next to rather than inside the corresponding female suction port inside the tank. Like prom night all over again.
If you are CERTAIN the ports are mated correctly, another common issue is one of the accordion hoses inside the tank has popped loose from the cup inside the tank. How did that happen? Well if someone tried to pull the whole assembly out without using the partially loosened bolt to push the cup down, then the cup gets pulled up and a hose can pop loose. Simple to reattach. The accordion hoses have two teeth on opposite sides. squeeze the connection perpendicular to these teeth and the hose pops free Squeeze the teeth toward each other with a pair of pliers to tighten the hose, snap it back on and that should work. These hose ends look like the plastic PCV hoses used in my now departed B7 A4.
To test that you got it right, remove the banjo bolt at the top of the pump assembly. find a threaded hose barb that matches the thread. Thread it in. Attach a length of cheap fuel hose to feed into a five gallon gas can. Remove the passenger' side front carpet. Open the relay box. Slide out the tray with the fuel pump relay. Pop the plastic cover off the FP relay. Wedge the relay contacts closed with a folded matchbook cover or thin piece of vinyl tube. Gently now. Turn the key to RUN, and the pump will run continuously. Pump out the tank into the gas can. Switch off, swap cans and keep pumping. When you can pump out the entire tank, you got it right. The Audi approved method for checking is drive it around and hope the engine doesn't quit. Idiots.
I actually had to make a "special tool" ...foot long hole saw... to remove my pump when the captive nut inside the tank broke loose. I drained the tank, filled it with a garden hose, cut out the assembly, shop vac'd the water, reached into the tank with a magnet to collect any filings, shop towels to the farthest recesses, took the cup out entirely, epoxied the nut, reattached all the inner hoses, new pump and assembly..10 years ago. No problems.
They probably just misaligned the pump on installation. Absent that, there is a loose accordion hose inside the tank where it attaches to the cup.
05-15-2018, 07:20 PM
#5
AudiWorld Senior Member
Thread Starter
Wow. Thanks for the detailed response Brian. That's what I want to checkout (tube connection) with the borescope. My car never had an issue running on gas below half a tank before the new pump.
Why does it have to be so hard to keep these cars running. UGH!
Why does it have to be so hard to keep these cars running. UGH!
05-15-2018, 10:43 PM
#6
AudiWorld Senior Member
It's easy if the tech is knowledgable
Or if you do it yourself. Borescope can access from the other fuel sender gauge access port on the left side of the trunk. That sender looks more like an old toilet bowl float rather than the silo incorporated into the fp assembly on the right side. The fuel gauge is an average of the readings from both sides.
Hey, when you rap the bolt, use a block of wood or dead blow hammer...not a steel hammer. Sparks over gas fumes is not desirable.
When setting the big rubber ring, lube it lightly with WD40 or a light oil to ease installation.
Good luck.
Hey, when you rap the bolt, use a block of wood or dead blow hammer...not a steel hammer. Sparks over gas fumes is not desirable.
When setting the big rubber ring, lube it lightly with WD40 or a light oil to ease installation.
Good luck.
05-18-2018, 04:17 AM
#7
AudiWorld Member
Nice writeup, BrianC72gt; thanks. The only nitpick could be your use of the term "siphon", since that means gravity flow from a higher location to a lower location, after getting starting with vacuum or some other method.
Sounds like you have fought this before! Pumping out the tank for confirmation is a really good idea. No guesswork.
Sounds like you have fought this before! Pumping out the tank for confirmation is a really good idea. No guesswork.
Trending Topics
05-22-2018, 06:19 PM
#8
Nice writeup, BrianC72gt; thanks. The only nitpick could be your use of the term "siphon", since that means gravity flow from a higher location to a lower location, after getting starting with vacuum or some other method.
Sounds like you have fought this before! Pumping out the tank for confirmation is a really good idea. No guesswork.
Sounds like you have fought this before! Pumping out the tank for confirmation is a really good idea. No guesswork.
I have pulled all of the guts from a d2 fuel tank...
It's not that difficult. I am betting you could find someone parting a car and get the part(s) you need.
-Richard
06-27-2018, 10:43 AM
#9
AudiWorld Senior Member
Thread Starter
UPDATE & RANT:
Took my car to an independent European shop. Dropped the car off at 8:30 with half a tank of gas, per their request. Four hours later the owner called and said the car is fixed. Before calling me, she had the tech drive the car around and listen for any sounds coming from the pump. He stated the pump was silent.
I picked my car, the shop owner told me to take the car and drive it around for a couple of days to make sure they fixed the issue. If all was good, come back and pay the bill. Sure, enough there was no noise coming from the pump and I ran the tank to 1/4 full with no issues.
I stopped back to pay the bill. Total charge out the door was $137.12. The issue was the bolt that clamps the fuel pump module to the lower part of the tank was loose. This might sound like a lot to tighten a bolt but Audi told me my tank failed and was going to charge me $2600 to fix it.
The funny or not so funny thing is: I was telling Audi for three weeks after they installed the new pump. That the pump was not installed correctly and that is why the pump is making noises and stalling out around half a tank. Audi guaranteed me the pump was installed correctly and the issue was with a "cracked transition" hose to the lower part of the tank.
Fuel pump problem solved. Now it's back to the dealer and talk with the general manager about this whole ordeal.
Thanks to everyone who chimed in on this.
Forum Users: What do you think would be an acceptable solution/compensation for my inconvenience?
Took my car to an independent European shop. Dropped the car off at 8:30 with half a tank of gas, per their request. Four hours later the owner called and said the car is fixed. Before calling me, she had the tech drive the car around and listen for any sounds coming from the pump. He stated the pump was silent.
I picked my car, the shop owner told me to take the car and drive it around for a couple of days to make sure they fixed the issue. If all was good, come back and pay the bill. Sure, enough there was no noise coming from the pump and I ran the tank to 1/4 full with no issues.
I stopped back to pay the bill. Total charge out the door was $137.12. The issue was the bolt that clamps the fuel pump module to the lower part of the tank was loose. This might sound like a lot to tighten a bolt but Audi told me my tank failed and was going to charge me $2600 to fix it.
The funny or not so funny thing is: I was telling Audi for three weeks after they installed the new pump. That the pump was not installed correctly and that is why the pump is making noises and stalling out around half a tank. Audi guaranteed me the pump was installed correctly and the issue was with a "cracked transition" hose to the lower part of the tank.
Fuel pump problem solved. Now it's back to the dealer and talk with the general manager about this whole ordeal.
Thanks to everyone who chimed in on this.
Forum Users: What do you think would be an acceptable solution/compensation for my inconvenience?
Last edited by 2001 S8; 06-27-2018 at 10:49 AM.
06-27-2018, 11:23 AM
#10
When I got my car it was on CPO warranty. It developed a bad front wheel bearing. Sounded exactly like a bad wheel bearing, any fool could hear. I could *not* get those bozos to agree it was a problem. They said it was tires so I put my winters on and came back. Then they said it was normal or they did not hear it. A few months later the wheel was louder and now quite loose, but my CPO warranty had expired. I took the car to the dealer and jacked it up in the parking lot, got the service manager to come out feel the loose wheel, shot wheel bearing, right there. He authorized the repair since the complaint was already in the system. I think he still had to go up the chain of command.
These Audi techs were the best Lexus salesmen I've ever seen. I was really blown away, $75K car new, only a couple years old, why not impress the buyer so they buy another high end Audi in a few years?
No, better to blow off the complaint and look like bunch of jerks and fools.
It does not seem to me like you should pay for all the work done by the dealer. Maybe the fuel pump install was done in good faith, you probably had a bad fuel pump, but they botched the install and you had to pay more labor to get it sorted out. So maybe not the labor?
These Audi techs were the best Lexus salesmen I've ever seen. I was really blown away, $75K car new, only a couple years old, why not impress the buyer so they buy another high end Audi in a few years?
No, better to blow off the complaint and look like bunch of jerks and fools.
It does not seem to me like you should pay for all the work done by the dealer. Maybe the fuel pump install was done in good faith, you probably had a bad fuel pump, but they botched the install and you had to pay more labor to get it sorted out. So maybe not the labor?