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OK, that does make sense. I was using a return system with the inline type pump (mounted to the frame rail) and finally got tired of the pump quitting, after a couple of years. Heat soak was finishing them off. No problem with the newer efi tank/in tank pump. Curious, wouldn't the evaporation of the gasoline in the tank help to cool to some degree? Does it stay in a liquid state, all the time with an EFI type of system? EFI doesn't get the vapor lock issue?

"Vapor lock - Wikipedia"
https://en.wikipedia.org/wiki/Vapor_lock

"Vapor lock is a problem that mostly affects gasoline-fueled internal combustion engines. It occurs when the liquid fuel changes state from liquid to gas while still in the fuel delivery system. This disrupts the operation of the fuel pump, causing loss of feed pressure to the carburetor or fuel injection system, resulting in transient ."
 

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OK, that does make sense. I was using a return system with the inline type pump (mounted to the frame rail) and finally got tired of the pump quitting, after a couple of years. Heat soak was finishing them off. No problem with the newer efi tank/in tank pump. Curious, wouldn't the evaporation of the gasoline in the tank help to cool to some degree? Does it stay in a liquid state, all the time with an EFI type of system? EFI doesn't get the vapor lock issue?

"Vapor lock - Wikipedia"
https://en.wikipedia.org/wiki/Vapor_lock

"Vapor lock is a problem that mostly affects gasoline-fueled internal combustion engines. It occurs when the liquid fuel changes state from liquid to gas while still in the fuel delivery system. This disrupts the operation of the fuel pump, causing loss of feed pressure to the carburetor or fuel injection system, resulting in transient ."
i would expect vapor lock isn't that common in an EFI system (e.g. return style) because it shouldn't typically experience the hot spot and also EFI is much higher pressure with moving not stagnant fuel.
 

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i have gauges on both my feed and return line, feed is around 65, return is less than 5.

(i've actually switched to a much lower max reading gauge for the return that reads the <5 psi, since it woudnt even move with the 100psi max one)
Interesting. 64 is a bit high. It should be 58 psi (4 bar). But it's not high enough to worry about or cause fueling issues. You'll get < 5% more fuel.

Return line is an open line so the psi is going to be whatever the pumping restrictions are. I'm surprised it's even 4 psi. I'd expect closer to 1-2.
 

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i would expect vapor lock isn't that common in an EFI system (e.g. return style) because it shouldn't typically experience the hot spot and also EFI is much higher pressure with moving not stagnant fuel.
I can be an issue. Like others have said the fuel pump is a heater (no motor is 100% efficient so you get heat from all of them). As an extreme, if you go put a 455 lph pump on a 80 hp 4 cyl it's going to vapor lock. The flowing fuel actually warms the whole system since it runs next to the engine plus the pump itself has efficiency losses and the fuel itself has friction. The only way you're going to get cooling is a tiny bit from adiabatic and convective to the fuel lines outside the car which isn't going to be much of a factor, especially during cruise on a hot day.

You can also get "vapor lock" if the tank manages to pull a suction. At some point the pump just can't pull enough fuel and the gas boils due to the pressure differential and you lose fuel line pressure because the pump can't move vapor (and it causes cavitation).
 

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OK, that does make sense. I was using a return system with the inline type pump (mounted to the frame rail) and finally got tired of the pump quitting, after a couple of years. Heat soak was finishing them off. No problem with the newer efi tank/in tank pump. Curious, wouldn't the evaporation of the gasoline in the tank help to cool to some degree? Does it stay in a liquid state, all the time with an EFI type of system? EFI doesn't get the vapor lock issue?

"Vapor lock - Wikipedia"
https://en.wikipedia.org/wiki/Vapor_lock

"Vapor lock is a problem that mostly affects gasoline-fueled internal combustion engines. It occurs when the liquid fuel changes state from liquid to gas while still in the fuel delivery system. This disrupts the operation of the fuel pump, causing loss of feed pressure to the carburetor or fuel injection system, resulting in transient ."
The inline pumps are mostly air-cooled. If you stick them in a stagnant air location they will cook themselves. The in-tank are fuel-cooled so they stay more consistent.

It's definitely possible to vapor lock an return-style fuel system (see my previous comment) but it's much harder than a carb with a dead-head fuel system.
 

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Discussion Starter #46
Interesting. 64 is a bit high. It should be 58 psi (4 bar). But it's not high enough to worry about or cause fueling issues. You'll get < 5% more fuel.

Return line is an open line so the psi is going to be whatever the pumping restrictions are. I'm surprised it's even 4 psi. I'd expect closer to 1-2.
yeah I dont.. think there are setting on it, nor does the EFI control the pressure? its just an... on and off right?
I know my injectors are LOUD... louder than other holley snipers i've seen.

we'll see what the new AEM pump runs at.
 

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yeah I dont.. think there are setting on it, nor does the EFI control the pressure? its just an... on and off right?
I know my injectors are LOUD... louder than other holley snipers i've seen.

we'll see what the new AEM pump runs at.
there will be a regulator in the unit. it won't be electronically controlled. the sniper and some (most?) fitech units will have a manifold reference to keep the pressure the same 4 bar/58 psi regardless of manifold pressure.
 

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"Spectra EFI Tank fuel pump became noisy - looking for better replacement options."


What took you so long? I don't necessarily agree with your assessment, but expected a pic of a carburetor much sooner than page 4.
 

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For people discussing fuel temps this thread a buddy of mine created might answer a lot of questions. I think he pretty much dispelled the myth that the pumps add a lot of heat to the fuel.

https://www.svtperformance.com/forums/threads/i-drastically-dropped-my-fuel-temps-by-over-100f.1030180/

I run a dead head on my 03 Cobra, but on my Massflo 351C and my FiTech 69 Mach I run a conventional return. The temperature difference between a dead head setup and conventional return is night and day. Before you couldn't even touch the fuel supply line on the car after a long drive, now its more or less ambient temp.
 

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to the outside through the bottom of the trunk dropoff.
Would something like this work? Run the hose up, basically as high as practical and down and then down. There is a factory hole in the drop off panel where a grommet could be used. Or maybe a convenient rust hole. The hose would just hang out a bit. If any gas does make it high enough to come out, it would hopefully just drip to the ground.The vapor is vented to the outside so no problems with odor?

 

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Would something like this work? Run the hose up, basically as high as practical and down and then down. There is a factory hole in the drop off panel where a grommet could be used. Or maybe a convenient rust hole. The hose would just hang out a bit. If any gas does make it high enough to come out, it would hopefully just drip to the ground.The vapor is vented to the outside so no problems with odor?

that would probably work fine. I've never noticed any residue or drips (i routinely clean the underside of my car) come out of mine. That factory hole in the dropoff near the wheel is the drain. the other hole was for the reverse lights.

I don't notice any odor with mine. when i ran a two way valve that took a little pressure to open either way, it seemed like it would almost burb on occasion.
 

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Discussion Starter #56
both, pressure or vacuum.

I welded a bung near the top of the filler tube for a barbed fitting. then ran a hose along the top, along the quarter and then down.





Is there an option to create a connection to the rubber connection between the filler neck and the tank? getting a bung welded on seems like a pain --- if there was just a way for me to tap the neck connector rubber piece... i think i'd be satisfied
 

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Is there an option to create a connection to the rubber connection between the filler neck and the tank? getting a bung welded on seems like a pain --- if there was just a way for me to tap the neck connector rubber piece... i think i'd be satisfied
I see no reason why you couldn't buy a 1/2"NPT tap and appropriate drill bit to accomplish the same thing as it's not under any kind of pressure. Add a little silicone goo on the threads for good measure. I just enlarged the hole in my cap from 3/32" to 3/16".
 

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Is there an option to create a connection to the rubber connection between the filler neck and the tank? getting a bung welded on seems like a pain --- if there was just a way for me to tap the neck connector rubber piece... i think i'd be satisfied
I haven't looked for any sort of rubber option. I'm fortunate to have the ability to weld, so it was very easy.
 

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I see no reason why you couldn't buy a 1/2"NPT tap and appropriate drill bit to accomplish the same thing as it's not under any kind of pressure. Add a little silicone goo on the threads for good measure. I just enlarged the hole in my cap from 3/32" to 3/16".
the filler neck tube is probably around 18 gauge, so not much to thread into.
 

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the filler neck tube is probably around 18 gauge, so not much to thread into.
Probably enough given the lack of any real pressure. I weld but might not bother to plug it in in this situation.

I personally would, and did, enlarge the vent hole in the cap. I would like to eventually make my cap not vented and vent the tank through a charcoal canister to eliminate the last bit of gas smell from my attached garage after a drive.
 
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