[Voodoo8648]

Hi, I just bought a 2007 BMW 328i N52 with GM tranny. I knew it had a bad misfire and bad coolant leak when I bought it but tried to drive it home about 2 miles anyways but the car shut off. So I had it towed it to mechanic and he said it needed a fuel pump and parts & labor would be $600. He replaced the fuel pump and told me it still has 3 cylinder misfires. He looked into it and said there was granules and dirt in the gas tank and said it needed to be flushed. He told me the tank would have to be dropped and that it's an 8 hour job. I told him to do it along with replace radiator. All in all the whole job cost $2,200 w/ parts and labor.

Well, after I got the car back, the motor runs great now but I noticed a tranny shutter at low RPM. Did some research and I decided to add Shutter Fixx to the trans fluid. So I got it up on the lift today and I was looking at the gas tank and noticed cobwebs were extending from the tank to the car's frame. I started looking at the bolts that are required to be removed in order to remove the tank and none of the bolts have been touched. It's obvious that the gas tank was NOT dropped.

So my question is what is required in order to properly flush the gas tank on this car? Can you do it WITHOUT dropping the tank? If so, how long would that take?

[Efthreeoh]

I'll have to check the Bentley to make sure, but I don't think it requires dropping the rear subframe to drop the fuel tank. You would need to drop the driveshaft and exhaust. But most all 3-series have access to the fuel tank from panels under the rear seat. The E90 is no exception; it has access to both sides of fuel tank through large openings on the top from under the rear seat. The right side is the fuel pump and fuel filter and fuel level sender combo and the left side is the left-side fuel level sender. If I were going to clean the tank, I'd go it it from the top side under the rear seat.

If the fuel tank was contaminated, then a good mechanic would replace the fuel filter, which is Integrated with the fuel pump, so a new fuel pump would be in order. He should have checked the old filter for contamination and not have to go back in.

It sounds like the shop wasn't quite honest with you, IMO. Misfires on 3 cylinders would not be a clogged fuel system issue if the mechanic implied the fuel filter is getting clogged. A simple fuel pressure test would be in order to diagnose it. And what three cylinders were misfiring? If it was 1, 2, 3 or 4, 5, 6 and not a mix then something else was the issue. The BMW inline 6 has two "cylinders banks"; cylinder bank 1 is cylinders 1, 2, and 3. Bank 2 is 4, 5, and 6. If all three cylinders from one bank were misfiring, then that's a fuel/ignition control issue. A clogged fuel filter would randomly affect fuel delivery.

In the future, get a scan tool and scan the car before you take it to the shop.

[E93Dude]

I'm more curious to see what resolution/restitution you get from the mechanic.

[tcphoto]

The OP made no mention of replacing the fuel filter, why do the fuel pump and ignore the filter?

[Voodoo8648]

Originally Posted by Efthreeoh

If the fuel tank was contaminated, then a good mechanic would replace the fuel filter, which is Integrated with the fuel pump, so a new fuel pump would be in order. He should have checked the old filter for contamination and not have to go back in.

Yeah, The first thing he claims he did was replace the fuel filter in order to get in running. After it got running, then he determined that it still had the multiple misfires.

But my biggest thing is regarding the flushing of the fuel tank as that was the highest priced labor item. 8 HOURS of labor.

he said it was also missing a gas cap and I think it was but my memory is vague because the car sat in his lot for 3 months before he even attempted to look at it.

[Voodoo8648]

Originally Posted by tcphoto

The OP made no mention of replacing the fuel filter, why do the fuel pump and ignore the filter?

According to the first commenter, the Filter is integrated with the fuel pump which the mechanic charged me to replace

[Voodoo8648]

So, Anybody have know if you can flush the fuel tank and lines without dropping the tank?

[Suvorovo]

Did you check any codes indicating bad fuel pump/system? Misfires could also be caused by bad coils which are cheap which you can do yourself in 1hr or a blown pcv valve.

[Efthreeoh]

Originally Posted by Voodoo8648

So, Anybody have know if you can flush the fuel tank and lines without dropping the tank?

Usually "dropping the tank" is required to gain access to the top of the tank where the opening is where the fuel pump is mounted into the tank. So other than being able to roll the tank over, there is no better access to the tank than through the fuel pump opening. Since the E90 gives full access to the top of the tank from under the rear seat, there no difference than just leaving the tank in the car and cleaning it vs. pulling the tank out and cleaning it. Anyway, rolling the tank over doesn't guarantee all the small granular contaminants would be removed. The fuel pump opening is approximately 4" in diameter from the few BMW tanks I've pulled the pumps from.

I've not had to flush the tank in any car, but after removing all the gasoline and letting the tank ventilate until all the fumes are gone, there are several ways to flush the tank. I'd use a shop vac and a garden hose with water.

The mechanic says he can see the granules of contamination. The granules are pretty big then I would suppose. So once the tank is clear of the fuel pump on the right side and the sender mechanism on the other side and of course gasoline and fumes so it is not explosive, a shop vac should be able to suck the contaminates off the bottom of the tank.

TBH I think the mechanic is bullshitting you.