Need Help Draining Fuel Tank...where's The Relay?

[ocd]

I searched for hours on google and came up empty. I need to drain the fuel tank on an R34 GTR. I'm working with limited space and tools. From what I've discovered, one cannot simply siphon the fuel tank with a hose. There appears to be some type of anti-siphon obstacle in the filler tube that obstructs any hose from slipping past.

Can anyone direct me, or at least tell me where the fuel pump relay is located? Any photos would be helpful. Knowing which color wires to run direct power to would be very helpful. I'm hoping to provide constant voltage to the fuel pump via the relay wiring and capture the fuel by removing the fuel line at the rail in the engine compartment.

Thanks in advance.

[StevenCJR31]

you wont get all the fuel out doing it that way, you need to take the fuel pump cradle out to get all the fuel out

[Tommy Kaira RL]

Just take off the fuel hose at fuel rail and turn car to on but dont start it. That's what I did when I converted to e85. I then put a bit of e85 in and pumped it out again.

[copycutter]

Just take off the fuel hose at fuel rail and turn car to on but dont start it. That's what I did when I converted to e85. I then put a bit of e85 in and pumped it out again.

^^ Same here exactly

[ocd]

you wont get all the fuel out doing it that way, you need to take the fuel pump cradle out to get all the fuel out

I'm not too concerned with getting all the fuel out. I just need to get as much as I can. I'll dillute the remainder with fresh gasoline.

Just take off the fuel hose at fuel rail and turn car to on but dont start it. That's what I did when I converted to e85. I then put a bit of e85 in and pumped it out again.

I was under the impression that the fuel pump will shut off after a moment without the engine acutally running. Did you have to keep cycling the key?

[jiffo]

Perhaps those cars had modified their electrics?

You're correct, the ecu will time out the pump in about 5 seconds.

Fuel pump relay should be in the boot, remove the panel in front of the number plate.

You should see 2-relays, fuel pump and ATTESSA pump.

[Tommy Kaira RL]

I'm not too concerned with getting all the fuel out. I just need to get as much as I can. I'll dillute the remainder with fresh gasoline.

I was under the impression that the fuel pump will shut off after a moment without the engine acutally running. Did you have to keep cycling the key?

My pump kept on going . Maybe the stock ECU has a 5sec timer but I doubt it. If your car was hard to start why would you want it to cut off. It wont take long to empty it even if you have to turn it on a few times. Its possible the 5sec comes from the fuel pressure reaching its pressure and fuel pressure relay shutting the pump off. With the hose disconnected the pressure wont hit the desired pressure so in theory will keep pumping.

[ocd]

Perhaps those cars had modified their electrics?

You're correct, the ecu will time out the pump in about 5 seconds.

Fuel pump relay should be in the boot, remove the panel in front of the number plate.

You should see 2-relays, fuel pump and ATTESSA pump.

I believe you are correct. Would you happen to know which wires to "jump" or "short" to have the pump run constant?

My pump kept on going . Maybe the stock ECU has a 5sec timer but I doubt it. If your car was hard to start why would you want it to cut off. It wont take long to empty it even if you have to turn it on a few times. Its possible the 5sec comes from the fuel pressure reaching its pressure and fuel pressure relay shutting the pump off. With the hose disconnected the pressure wont hit the desired pressure so in theory will keep pumping.

Most modern vehicles will shut off the fuel pump if the ecu doesn't see the engine has started (rpm based?). As far as I'm aware, there is no electrical fuel pressure sensor signal. I know you can run the engine and disconnect the fuel return as a drain until the tank runs empty, but my engine doesn't run.

Edited April 30, 2013 by ocd

[jiffo]

 

My pump kept on going . Maybe the stock ECU has a 5sec timer but I doubt it. If your car was hard to start why would you want it to cut off.

 

Mate all ecu equipped vehicles have a safety cut on the fuel pump. Some use a timer, others use engine oil pressure, anything to tell the ecu that the engine has stalled.

Not rocket science, you don't want fuel pumping over a crash scene, that's the reason.

The stock pump will prime in those 5 seconds but some aftermarket items without a non-return valve will need a few key on/offs to fully prime.

Direct wiring of a street car's fuel pump is one defect I'll endorse.

[Tommy Kaira RL]

   

Mate all ecu equipped vehicles have a safety cut on the fuel pump. Some use a timer, others use engine oil pressure, anything to tell the ecu that the engine has stalled.

Not rocket science, you don't want fuel pumping over a crash scene, that's the reason.

The stock pump will prime in those 5 seconds but some aftermarket items without a non-return valve will need a few key on/offs to fully prime.

Direct wiring of a street car's fuel pump is one defect I'll endorse.

Yes well that would make sense. I better have a look at how my Tomei fuel pump rewire is done. I even remember having to put a pressure switch in line with a fuel pump once to do the exact thing you stated. Thanks

[ocd]

Update:

I found the fuel pump relay with the help of a well informed friend. It's located under the passenger side tail light assembly, underneath the interior trunk panels. It's pretty easy to get to, but locating it was challenging. It's relay number 62. I attached a diagram for anyone in the future that needs to evacuate their fuel tank this way. I removed the relay and jumped terminals 3 and 5 with a medium gauge wire (the relay terminal #'s are labled on the relay itself). Then, when you turn the ignition to the on position (enging NOT running), the fuel pump will continuosly run until the tank is empty. I removed the fuel hose from the filter to the fuel rail, connected a hose junction and a length of fuel hose to a gas container. It didn't take very long to empty half a tank of petrol. Keep a close eye on the fuel meter, you don't want to run the fuel pump without fuel too long.

Edited May 18, 2013 by ocd

[ocd]

[benjaminpwarren]

I had to do this on my stock 2001 R34 GTT sedan and I can confirm that bridging terminals 3 and 5 on the relevant relay plug allows the fuel to pump continuously when the ignition is on.

Some other points/info:

• The relays aren't on the passenger side, they're on the right-hand side.
• Your relays might have been swapped around or mounted incorrectly/differently in the first place, as mine were, compared to the above relay location pic. If you've bridged the correct relay plug, fuel will pump solidly out of the whole diameter of the fuel line hose (rather than just a brief trickle if you've got the wrong relay). Dunno what the other relay is for, I'm hopeful that nothing has been borked.
• The fuel line hose is 5/16". I bought mine from Supercheap Auto. It was approx. $10/m. In hindsight, I should have found a cheaper type of hose as one doesn't really need a rated hose for just transferring fuel. For example, Bunnings has 8mm hose for less than half the price (they were out of the 8mm size when I needed it).
• Get about 2m of hose. This way you've got plenty of room, particularly if you're pumping into another vehicle.
• You'll need a joiner, too. I bought mine from Supercheap Auto (also costs more than it should). Later discovered that the plastic "shell" of a pen/biro is the perfect size, and gives you a viewing window if it's a clear plastic!
• The easiest way to identify which hose is the fuel line is to look for the fuel filter. The fuel filter casing has "OUT" written on it.
• The fuel line was pretty hard to pull off. We ended up gripped it with some pliers (GENTLY) near the end and just rotating/jiggling it a very small amount. This then allowed me to pull it off with great effort.
• You don't need to purchase or use hose clamps just to transfer the fuel, friction is enough to hold the hoses onto the joiners. In fact, don't push your hoses onto the joiner too tightly, you'll struggle to get them back off.
• It takes a surprisingly small amount of time to pump a large amount of fuel, so keep an eye on your gauge(s).
• Skyline screw trim fasteners are stupid. In fact, most trim fasteners are stupid.

Siphoning

Whilst we ended up discovering that the fuel pump relay method wasn't working because we had the wrong relay, we did attempt to siphon out the fuel using the traditional hose-down-into-tank-and-suck method.

It was actually perfectly easy to get a hose down into the tank, so perhaps there isn't an anti-siphon device in there after all. The 'pipe' down to the tank does turn to the right, perhaps this is what other people had difficulty with or perhaps there's something model-specific that's different.

We confirmed that we'd reached the fuel by blowing air into the hose and listening for the bubbles.

We decided not to use this method as there was no practical way for us to get Car B lower than Car A and siphoning into a Jerrycan would have taken too long (we only had a 5L "Jerrycan").