Major Problem?!?! Dies at half full tank!!

[TDIFLA]

Hello!
I've been searching all over and can't find the answer to my problem. Hopefully someone can help??!!??

Long story short....
2006 Jetta TDI
Put unleaded in my TDI(I'm an idiot!)
Towed to dealer and after flush and such, was given a clean bill of health.
Car was driving fine, until I hit a half tank of fuel. It just plain died and wouldn't start.
Towed back to dealership, who couldn't find the problem to save their lives.

After $600 later and a new fuel pump(that's what they thought was the problem to no avail) the problem is still there.

Car runs great as long as it not at half full or parked on a hill. MPG is 41!
I've checked fuel lines and such and no problem.

Does anyone have ANY idea what might be causing this?

Thanks in advance!!!!

[Quantum TD]

On on the old IDIs, if the water-separator was full of water, or the fuel pump screen was clogged, the car would cut out going around corners or below a hlf tank.  I'm not sure what your car has, but I'm going to assume that it at least has a water separator on the bottom of the fuel filter. I'd drain that completely and or replace the filter. There may also be another separator under the car (again, not sure).

If the engine runs fine except for cutout at 1/2 tank, then it can't be anything major. The old engines were ok with some unleaded (the manuals for the old Rabbits encouraged you to mix 10-30 % unleaded in the winter to prevent gelling). So, the unleaded is not the issue. I think that you might be getting straight unleaded at times. Either they didn't drain the tank completely, or there's unleaded in the filter. Presumably, gas is less dense than diesel, so if there's still some gas in there (about a half a tank?), then the transer pump will be pulling diesel from the bottom of the tank, then it hits the unleaded and cuts out.

Either way, it's a toughie. I'd check the filter/separator first. I don't know what electronic mechanisms the newer cars may have that would cut out the fuel. But based on the old cars, and what you're describing, then it shouldn't be anything major. And to be honest, I don't know how the transfer/lift pump could be affected by gas fuel. It's just another liquid, and the dealer probably didn't need to replace it. My best bet is that the filter is full of str8 gas.

Let us know how it goes.

[MikkiJayne]

I've heard of this on Corrados before when the lift pump (or fuel pickup) was damaged. If there is a hole or crack in the assembly above the half tank level it can pull in air instead of fuel.

I would guess they took the lift pump out to drain the tank, and possibly damaged it or dislodged something in the process. If a filter change doesn't help I'd be looking at replacing the lift pump next.

Mikki x

[jtanguay]

well 2006 TDI should be a PD engine.  since there is no pump to change (injection pump), there only lies the lift pump at the back, and i think there is another pump on the engine itself (that is a mechanical feed pump).

was the car ran on the gasoline/diesel mixture for any amount of time??? if not i'd say the problem is completely their fault.  they probably didn't hook something back up properly.  i know some of those fuel tanks have different chambers/compartments and there is a pump that disperses fuel or equalizes fuel between chambers (to stop fuel cutting out going around tight corners maybe or on hills maybe) but that might just be on audi's

[Quantum TD]

Yeah. That's a good point. The lift pump is often integrated with the fuel sending unit. In order to make it all work, there is often a long tube with the lift pump at the end of it. The tube attaches to the lift pump and rides along a rubber seal.  The tube usually goes down 1/2 of the height of the tank, then the lift pump takes up the other 1/2.

What may be happening is one of two things:

1) The lift pump is not working at all. The injection pump is doing all the work and when it hits 1/2 tank, the tube is at the end of it's length, and it starts sucking air.

2) The pump is working, but the stealership forgot to install/replace the rubber seal on the pump, or it tore when they reinstalled it.

In either case, you'd be sucking air. That's easy enough to look for. When the tank get's near 1/2, open the hood and watch the clear tube looking for bubbles. If/when the car stalls, you see air bubbles, you know the problem is in the tank.

So, i guess final word on my end: change the filter, then look to the tank pickup system. I think that fault may eventually end up in the dealer's hands.

Good luck.

[jtanguay]

another thing is that i think if you run the PD injectors dry you can seriously damage them.  i may be wrong, but i wouldn't want to be the one to find out...

[Greasecar]

The PD Has an in tank electric pump and a mechanical high pressure pump driven off the cam shaft with a filter water seperator under the hood and a fuel cooler in the return line of automatic models.  The '06 fuel filter is really funky with at least 4 fuel line barbs that I do not belive are labeled.  You may want to make sure the lines are on the correct barbs (the lines themselves are labeled with blue or white arrows on the ends).  If the feed and return line to the tank are swapped that could explain why it stops pulling fuel at half tank since the return line doesn't go to the bottom.  There is also a feed and return connection on the sending unit on top of the tank, they could be switched there ( be warned, this is under the rear seat on the pass side and is a real pain in the ass to get at)

$.02

[jtanguay]

good knowledgeable advice greasecar thanks.  

now if i can translate what that all means:  take car back to dealership and in nicer words, tell them that they f*@#$ed up and need to fix it.  :lol: