Strange fuel leak

Car is a 2003 mercury sable GS, V6 engine.

Fuel is leaking from the top of the gas tank only when the engine is running. With the key in the run position i can hear the fuel pump turn on and pressurize the system and there are no leaks. It only leaks when the engine is running. The fuel pressure is within specs. Only 50k miles. New fuel filter installed. Using shell regular unleaded gas. No OBD codes when scanned. Check engine light is off.

Any idea why it only leaks when the engine is running?

I did a google search for this problem, no usefull results.

Best Regards Tom.

"Howard Beal" fired this volley in news:ls8lkl$ebu$1 @speranza.aioe.org:

Sure. The system slightly pressurizes the tank so that tank vapors are passed back into the intake system.

Shouldn't BE any leaks; the system is designed to be airtight. If so, it's probably a sensor/fuel-pickup gasket problem... but it could be a bad seam. That's something that needs attention NOW!

In the meanwhile, run your tank no more than 1/2 full to prevent the leak.

Lloyd

Just went out and removed the gas cap so there is no pressure in the tank still leaks when engine is running.Unlikley to be a bad seam, this car is in las vegas and does not have any corrosion issues. Tank looks like factory new. Only has a 1/4 tank of gas.

Best Regards Tom.

Thanks for the link. A very good knowledge base for taurus/sable owners. Saved to my favorites.

Best Regards Tom.

"Howard Beal" fired this volley in news:ls8qdv$r15$1 @speranza.aioe.org:

You said it was leaking from the TOP. If no pressure, and only 1/4 tank, then it's got to be the recirculation hose leaking. Excess fuel from the injector rack goes back to the tank.

LLoyd

There ya go buying those cheap after-market parts.

The fuel pump in my Blazer failed (at 180k). Right at $1000 from Chevrolet.

I tend to agree, still gonna have to drop the fuel tank to fix it. Gonna rerout the fuel return line into a gas can and see if the leak stops. I just hope its not a cracked or broken fuel pump output port. New fuel pump is $250.00 Damn things are all plastic, i don't think they are repairable.

Best Regards Tom.

Thats what i am thinking. Still a big PIA to fix, gotta drop the gas tank. Luckly it's only gonna be 110 in the shade tomorrow. Its about a 3 hour job according to reports from people who done it.

Best Regards Tom.

Many EFI systems use a fuel return line to route excess fuel from the pump back to the tank. You probably have a bad line at the tank, where it switches from steel/copper to rubber to mate with the tank.

I suggest dropping the tank and replacing all lines there, as well as any other fuel line rubber on the vehicle.

Yep goona replace all the old lines on the gas tank. I have to drop the gas tank to see whats going on, might as well replace those 11 year old hoses.

Best Regards Tom.

Wow thats a pricey fuel pump.

Best Regards Tom.

Particularly if there is a rubber hose involved in the return line. Hot nevada temps - cracked rubber hose - leak when running.

The 7' bed comes off my '91 easily, thanks to LPS-3.

Insert a plank or plywood between the bed and the cab to avoid scratches.

Cut a knot-free 2x6 long enough to catch the lips at the top of the sides. Put an eye bolt (not screw) in the middle. Set it across the fender wells. The lift eye reminds me not to cut it up for something else. The pullout rating of a 3/8" eye -screw- in pine is marginal for this.

Unplug the electrical connector below the tailgate and remove the three screws behind the gas cap that hold the filler tube.

Remove the six T-55 bed bolts.

Roll up the shop crane and lift the bed barely clear, then check for anything missed. I have to remove the gas cap to free the filler tube. It's easier to pull through or reinsert in the hole when the bed is slightly raised and swinging free.

Lift the bed above the bumper and roll it away. I leave it upside down on cribbing to more easily inspect and repair it.

-jsw

The return line to the tank from the fuel pressure regulator probably has a leak where it connects to the top of the tank. When the engine is running there is return flow, when not running no return flow. If you jumper the fuel pump relay to run the pump with the engine not running you should see the same leak. When you turn the key on, it only pumps for a few seconds, not enough to push much if any fuel back through the return line.

Check prices at Rock Auto:

Just took a quick look and they must have had 20+ different fuel pumps available with prices starting ~$30. Even if I don't buy from them I always check pricing to see how bad the local guys are jabbing me...