15 replies to this topic

[IronmanG]

I have finally fitted the tank to the PUP and I have 2 questions.
I am running injection. MS states a non vented petrol cap for injection. I just want to confirm that's right.
Secondly there isnt much of the tank sticking through the body work to allow a cap to fit on. See pic. Is that enough?  Screenshot_20210608-153637_Gallery.jpg   12.8K   2 downloads

[nicklouse]

Pup would normally have a vented cap as there is no tank vent. But as you are running injection you want a NON vented cap.

[Steve220]

As you have no other way of reducing the pressure in the tank, i'd go vented.

 

Non-vented is only for systems that have a charcoal canister that can purge the excess pressure, otherwise you'll slowly get a heavily pressurised tank.

 

As I have binned the charcoal system on my MPi and blocked up the 3rd pipe, i run a vented cap.

[Steve220]

Out of curiosity, how have you done the fuel return into the tank?

[IronmanG]

I am running a return to the tank via a swirl pot if that makes a difference

[IronmanG]

Out of curiosity, how have you done the fuel return into the tank?

When it's a bit tidied I will post a picture!
I had a return pipe welded in

[IronmanG]

Bump

[nicklouse]

As you have no other way of reducing the pressure in the tank, i'd go vented.

 

Non-vented is only for systems that have a charcoal canister that can purge the excess pressure, otherwise you'll slowly get a heavily pressurised tank.

 

As I have binned the charcoal system on my MPi and blocked up the 3rd pipe, i run a vented cap.

Ohhhhh I forgot about the carbon canister.

[Gabor]

HI,

 

Do you have the purge valve, and/or the canister? Deffinetly the non vented cap is needed for the injection, because the fuel pump needs relative system presure to work fine, and this way it does not run the system that lean neither. It will work with the non vented cap as well, but it will slowly damage the fuel pump, because of the lack of the system pressure, and the fuel pressure will descend in the system when you turn of the engine, and this way the pump needs to build up the system presassure every time when you start the engine. So if you have the canister and the fuel purge system built to your pup, than go to non vented caps. If you do not have these, than you can not keep the system under constant pressure, and it will run too, but firmly leaner and the fuel pump will be worn out sooner. 

 

Regardin the cap, that should be enough gap.

 

Drive safe

G

Edited by Gabor, 09 June 2021 - 02:26 PM.

[Steve220]

HI,

 

Do you have the purge valve, and/or the canister? Deffinetly the non vented cap is needed for the injection, because the fuel pump needs relative system presure to work fine, and this way it does not run the system that lean neither. It will work with the non vented cap as well, but it will slowly damage the fuel pump, because of the lack of the system pressure, and the fuel pressure will descend in the system when you turn of the engine, and this way the pump needs to build up the system presassure every time when you start the engine. So if you have the canister and the fuel purge system built to your pup, than go to non vented caps. If you do not have these, than you can not keep the system under constant pressure, and it will run too, but firmly leaner and the fuel pump will be worn out sooner. 

 

Regardin the cap, that should be enough gap.

 

Drive safe

G

 

Total myth reference the fuel pump damage.

 

https://itstillruns....ct-7302130.html

 

The longevity or output of the pump is not a function of the pressure in the tank. Otherwise manufacturers such as Walbro, DeatschWerks, AEM, Bosch etc. would state tank/atmospheric conditions for their datasheets. The reason the pressure rises is due to warmer weather and the returning fuel being warmer as it flows around the engine, the car uses this to purge the vapour back into the engine in a closed loop EVAP system to prevent over pressurising. When we talk about pressure, the tank is maintained BARELY above atmospheric due to EVAP, but due to the size, makes a large hiss (usually you get it below half a tank of fuel). The reason we have sealed caps is due to air polution (unburnt hydrocarbon emissions (UHC)) and safety against ignitable vapour. It has nothing to do with the pump longevity as they simply do not work that way.

Edited by Steve220, 09 June 2021 - 03:41 PM.

[IronmanG]

 Screenshot_20210609-202710_Gallery.jpg   18.88K   4 downloads  Screenshot_20210609-202715_Gallery.jpg   19.54K   4 downloads

Is this vented?

[IronmanG]

 Screenshot_20210610-172038_Gallery.jpg   14.85K   12 downloads

@Steve220

[Steve220]

Screenshot_20210610-172038_Gallery.jpg

@Steve220

Cheers mate!

[Gabor]

Thank you for expressing your opininon. I accept it, that yours if different than mine.

 

HI,

 

Do you have the purge valve, and/or the canister? Deffinetly the non vented cap is needed for the injection, because the fuel pump needs relative system presure to work fine, and this way it does not run the system that lean neither. It will work with the non vented cap as well, but it will slowly damage the fuel pump, because of the lack of the system pressure, and the fuel pressure will descend in the system when you turn of the engine, and this way the pump needs to build up the system presassure every time when you start the engine. So if you have the canister and the fuel purge system built to your pup, than go to non vented caps. If you do not have these, than you can not keep the system under constant pressure, and it will run too, but firmly leaner and the fuel pump will be worn out sooner. 

 

Regardin the cap, that should be enough gap.

 

Drive safe

G

 

Total myth reference the fuel pump damage.

 

https://itstillruns....ct-7302130.html

 

The longevity or output of the pump is not a function of the pressure in the tank. Otherwise manufacturers such as Walbro, DeatschWerks, AEM, Bosch etc. would state tank/atmospheric conditions for their datasheets. The reason the pressure rises is due to warmer weather and the returning fuel being warmer as it flows around the engine, the car uses this to purge the vapour back into the engine in a closed loop EVAP system to prevent over pressurising. When we talk about pressure, the tank is maintained BARELY above atmospheric due to EVAP, but due to the size, makes a large hiss (usually you get it below half a tank of fuel). The reason we have sealed caps is due to air polution (unburnt hydrocarbon emissions (UHC)) and safety against ignitable vapour. It has nothing to do with the pump longevity as they simply do not work that way.

 

Edited by Gabor, 11 June 2021 - 01:58 PM.

[Steve220]

 

Thank you for expressing your opininon. I accept it, that yours if different than mine.

 

HI,

 

Do you have the purge valve, and/or the canister? Deffinetly the non vented cap is needed for the injection, because the fuel pump needs relative system presure to work fine, and this way it does not run the system that lean neither. It will work with the non vented cap as well, but it will slowly damage the fuel pump, because of the lack of the system pressure, and the fuel pressure will descend in the system when you turn of the engine, and this way the pump needs to build up the system presassure every time when you start the engine. So if you have the canister and the fuel purge system built to your pup, than go to non vented caps. If you do not have these, than you can not keep the system under constant pressure, and it will run too, but firmly leaner and the fuel pump will be worn out sooner. 

 

Regardin the cap, that should be enough gap.

 

Drive safe

G

 

Total myth reference the fuel pump damage.

 

https://itstillruns....ct-7302130.html

 

The longevity or output of the pump is not a function of the pressure in the tank. Otherwise manufacturers such as Walbro, DeatschWerks, AEM, Bosch etc. would state tank/atmospheric conditions for their datasheets. The reason the pressure rises is due to warmer weather and the returning fuel being warmer as it flows around the engine, the car uses this to purge the vapour back into the engine in a closed loop EVAP system to prevent over pressurising. When we talk about pressure, the tank is maintained BARELY above atmospheric due to EVAP, but due to the size, makes a large hiss (usually you get it below half a tank of fuel). The reason we have sealed caps is due to air polution (unburnt hydrocarbon emissions (UHC)) and safety against ignitable vapour. It has nothing to do with the pump longevity as they simply do not work that way.

 

 

 

I wasn't giving an opinion. I was telling you why you were wrong, with facts.