Billy Ryan Posted February 26, 2006 Share Posted February 26, 2006 I have been trying to figure out if when doing the RB swap, does your gas tank have to be under pressure? I have read multiple things on the forum and to be honest, I am confused. Some have said that when running EFI, the tank is required to be under pressure. Some others have said the opposite. So which one is it? Pressurized or not? Quote Link to comment Share on other sites More sharing options...
Ed260Z Posted February 27, 2006 Share Posted February 27, 2006 To the best of my knowledge, the tank doesn't ever need to be under pressure. Quote Link to comment Share on other sites More sharing options...
Billy Ryan Posted February 27, 2006 Author Share Posted February 27, 2006 Some people have said that they plug the vent lines. Doesn't that leave the tank under pressure? Quote Link to comment Share on other sites More sharing options...
Ed260Z Posted February 27, 2006 Share Posted February 27, 2006 People plug some of the vent lines, but not all. If you plug them all you will not be able fill the tank all the way, and you will have fuel starvation as the tank empties. Quote Link to comment Share on other sites More sharing options...
alexideways Posted February 27, 2006 Share Posted February 27, 2006 People plug the "vents" that are used for EVAP on a OEM not frankensteinized, 20 years older than the engine car. EVAP works by constantly checking depression in the tank, if it reads athmospheric pressure, the check engine light comes on and it can mean either thing, 1-Your gas cap is'nt tightened properly(most common problem) or 2:you have a leake somewhere in the closed circuit EVAP system. Quote Link to comment Share on other sites More sharing options...
EMWHYR0HEN Posted February 27, 2006 Share Posted February 27, 2006 I don't have an exact answer for you. but, I can say that im using my stock tank and its not under pressure, i have a walbro external, and I havnt ran into any problems....but if you ask me, doesnt sound right to put a once 'carbed' tank into a pressurized one, esp if your not gonna modify it. Since this is a Gas tank topic..... Quick question to anyone with 240Z with EFI..... is it necisary to keep the stock fuel vent device ( I think thats what it is?) when swapping to EFI? its the black, weird shaped canister behind the passenger side quarter pannel. The only thing I notice from that thing is the smell of gas fuems inside the cockpit. So what guys, Toss it? Quote Link to comment Share on other sites More sharing options...
Ed260Z Posted February 28, 2006 Share Posted February 28, 2006 If your smelling gas it's because you need to replace those 30yr old + lines. If your getting rid of the Evap controll system you can loose it. But as of yet I haven't heard a good reason to get rid of the Evap Sys. Quote Link to comment Share on other sites More sharing options...
240zwannabe Posted February 28, 2006 Share Posted February 28, 2006 if EFI gas tanks aren't under pressure then why does my tank make a psshh noise when i open it to put in gas every other day or so? Quote Link to comment Share on other sites More sharing options...
240Z_Master Posted February 28, 2006 Share Posted February 28, 2006 if EFI gas tanks aren't under pressure then why does my tank make a psshh noise when i open it to put in gas every other day or so? Certain systems have different ways of doing this. I'm still confused on the whole topic. As for me, I plan to plug all but 1 of the vents on top of the gas tank. I'm still going to be concerned with the return line and the surge tank though. I might route the return from the surge tank, back to the original gas tank. Quote Link to comment Share on other sites More sharing options...
RB26powered74zcar Posted February 28, 2006 Share Posted February 28, 2006 if EFI gas tanks aren't under pressure then why does my tank make a psshh noise when i open it to put in gas every other day or so? I think they are under vacum, not presure... Quote Link to comment Share on other sites More sharing options...
stony Posted February 28, 2006 Share Posted February 28, 2006 I think they are under vacum, not presure... Joel beat me too it.... you gas tank has created somewhat of a vaccuum because you have taken fuel out of it without letting any air in. The only crap i had left on mine before i went to a cell were the one or two vent lines that went up to the fuel cap area. everything else got pulled and scraped except the hard line going to the front of the car. hope this helps Quote Link to comment Share on other sites More sharing options...
alexideways Posted February 28, 2006 Share Posted February 28, 2006 if EFI gas tanks aren't under pressure then why does my tank make a psshh noise when i open it to put in gas every other day or so? As I said earlier, EFI tanks work under vacuum. The reason for this is the ECU monitors vacuum under specific conditions an can determine if there is a leak in the "CLOSED CIRCUIT" EVAP system. If ECU sees Atmospheric pressure, there is a leak. The PSSSSHHH sonf you hear is the expended gas "vapors" that comes out when you "open" the "closed circuit". Quote Link to comment Share on other sites More sharing options...
240zwannabe Posted February 28, 2006 Share Posted February 28, 2006 oh ok, for some reason i must have looked over your first post. it sense to me now. Quote Link to comment Share on other sites More sharing options...
Ed260Z Posted February 28, 2006 Share Posted February 28, 2006 Certain systems have different ways of doing this. I'm still confused on the whole topic. As for me' date=' I plan to plug all but 1 of the vents on top of the gas tank. I'm still going to be concerned with the return line and the surge tank though. I might route the return from the surge tank, back to the original gas tank.[/quote'] The vent lines on the tank are there to allow the fuel to fill all the way up. If you look at your tank you will see that it has a few high spots, (so that it can conform to the floor of the car.) and the vent lines are connected there. You might loose 1/2 to 1 gallon of capacity if you plug up most of the lines. Right now I'm toying with the idea of heavily modifying my 260Z tank. I'm going to divot the lower pass side, to allow for a twin exhaust. And then run new Exit and return lines of the size I want. -8 & -6. I might also remove the tire well, and weld in an extension on the top of the tank. (for more capacity) All of this will require me to split the tank open, and of course learn how to weld. LOL Quote Link to comment Share on other sites More sharing options...
240zwannabe Posted February 28, 2006 Share Posted February 28, 2006 the welding part is easy, just be careful with the thin metal, dont let it get too hot. if your going to take out the wheel well and put on an extension why not just put in a fuel cell? Quote Link to comment Share on other sites More sharing options...
240Z_Master Posted February 28, 2006 Share Posted February 28, 2006 the welding part is easy, just be careful with the thin metal, dont let it get too hot. if your going to take out the wheel well and put on an extension why not just put in a fuel cell? Yeah, I might just put a fuel cell in my car to solve those problems too. Then build some kind of cover for it for SCCA safety regulations. Quote Link to comment Share on other sites More sharing options...
Ed260Z Posted February 28, 2006 Share Posted February 28, 2006 the welding part is easy, just be careful with the thin metal, dont let it get too hot. if your going to take out the wheel well and put on an extension why not just put in a fuel cell? I want to keep the stock filler location. And from what I've seen most if not all of the cells fill in the middle of the tank. I would need to drop the cell pretty low to have enough clearance to run a filler neck. A fuel cell would be the simplest way to get it done, the way I want. Do you know of a way to run the filler from the stock location? The only examples I've seen run the tube through the cargo area, which I don't want. Another thing is that I also want to keep the stock gauges, and the GM sending units won't work with the Datsun fuel gauge. Quote Link to comment Share on other sites More sharing options...
240Z_Master Posted February 28, 2006 Share Posted February 28, 2006 I want to keep the stock filler location. And from what I've seen most if not all of the cells fill in the middle of the tank. I would need to drop the cell pretty low to have enough clearance to run a filler neck. A fuel cell would be the simplest way to get it done, the way I want. Do you know of a way to run the filler from the stock location? The only examples I've seen run the tube through the cargo area, which I don't want. Another thing is that I also want to keep the stock gauges, and the GM sending units won't work with the Datsun fuel gauge. There might be some kind of side feed fuel cell, but I'm not sure how well they work or if they exist. Quote Link to comment Share on other sites More sharing options...
Ed260Z Posted February 28, 2006 Share Posted February 28, 2006 There might be some kind of side feed fuel cell, but I'm not sure how well they work or if they exist. I've looked, and it seems that it's only a custom cell. As in $$$$$$$$$$. If I could find a cell with an off center filler I could use a 45*neck, and a remote filler from Summit. I'm already going to be spend $1K on the fuel system, so whats another $300 or so. Quote Link to comment Share on other sites More sharing options...
240Z_Master Posted February 28, 2006 Share Posted February 28, 2006 I've looked, and it seems that it's only a custom cell. As in $$$$$$$$$$. If I could find a cell with an off center filler I could use a 45*neck, and a remote filler from Summit. I'm already going to be spend $1K on the fuel system, so whats another $300 or so. Hold your wallet in your own pocket mister money bags! Quote Link to comment Share on other sites More sharing options...
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