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Draining bad gas

10K views 5 replies 3 participants last post by  b4black 
#1 ·
Hello everyone,


I am trying to drain some very old gasoline from a 2009 Mazda 6. I'm hoping it's the cause of a no start issue. (The fuel is at least 4 years old.)


I disconnected the fuel line from the rail and connected a hose to a gas can. Typically I just jumper the fuel pump relay and that energizes the fuel pump until it pumps out all the fuel. In this case, when I jumper the fuel pump, it runs for a couple of second and then shuts off. Each time I jumper it, same thing - about 2 seconds and then off again.


If there another easy way to run the fuel pump with the engine off?
 
#2 ·
Yeah its a PITA. The PCM cuts off the pump if there is no pressure at the fuel rail - safety thing I suppose. Here's what I did:


Pull the pump and syphon the fuel to get most of it.








Drop the tank and clean it inside and out.





Add a drain plug so I don't have to do this again.





Good luck!
CR
 
#3 ·
Drop the tank and clean it inside and out.
+1. I know it's not what you wanted to hear, but you're going to have to drop the tank and clean it. You won't be able to get all the crap out otherwise. You also won't be able to get all the fuel out, even if you could run the pump dry (which is a bad idea because you risk burning up the pump). There's a certain amount of unusable fuel in every fuel tank that would get left behind, along with all the crud, sediment, etc.

Without cleaning the tank, as soon as you put new gas into the tank, all that crud and crap and nonsense gums up the fuel pump and the fuel filter again.

That will also give you an opportunity to inspect the fuel pump, clean the pickup, etc.
 
#4 ·
I appreciate the pictures and all, but that's exactly what I am trying to avoid. I won't be dropping the tank. There's no crud or sediment or water in the fuel.


The fuel is low on vapor pressure. I just need to get most of it out and add some fresh winter gas (with high vapor pressure).


I read something about grounding a pin a "check connector" in the fuse box. Tried that, but it didn't work, but I'm not sure if I grounded the correct pin or not. Anyone familiar with the check connector?
 
#6 ·
Bypassing the FPCM worked. Pin 1 on the connector (female, green/black wire) is 12 volts from the underhood relay. Jump it to pin 5 (white/black) which is power to the fuel pump. Then ground pin 8 (brown/yellow) to chassis or pin 4 (black/red).


With the FPCM bypassed, jumping the fuel pump relay in the fuse block turns the pump on and it stays on.


Fresh gas and the car finally starts. :)
 
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