Aftermarket EFI and dual internal pump tanks

[Fastduramax]

Is anyone here successfully running dual Sniper EFI conversion return style tanks (pump and separate fuel sender model) with a Pollak or other brand 6 port selector valve with either PF4 or Sniper EFI ? This is my current goal but don't know if it's even possible never mind how to correctly do it !

 

[bluex]

Everytime I've tried it, it gives me trouble. The valves wind up failing an returning fuel to the opposite tank it's pulling from, which overflows that tank. I tell people to install a rear mounted tank from a 87 blazer. The 25 gal fits good for a shortbed an a 31 or even a 40 will work for a longbed. Just got to watch the ground clearance with a 40 on a lowered one.

 

[Fastduramax]

Thanks Blue I expected a Blazer tank reply for sure, does anyone make a conversion kit or you gotta mock/fab it up on your own ? Just sucks I already have 1 Sniper conversion tank full kit and was kinda just hoping to buy another and make it all work in harmony! Also the 31 won’t fit in a shorty ?

 

[bluex]

Thanks Blue I expected a Blazer tank reply for sure, does anyone make a conversion kit or you gotta mock/fab it up on your own ? Just sucks I already have 1 Sniper conversion tank full kit and was kinda just hoping to buy another and make it all work in harmony! Also the 31 won’t fit in a shorty ?

Not if its lowered it won't. It'll get into the rear axle. Boyd welding or No limit might build you a custom one with more capacity if it's necessary. I think those are around 20 gals or so.

Other people have had luck getting the dual tanks to work, I just never have.

Is there a reason you'd have to have the dual tanks? If you've done a overdrive upgrade as well with the efi you should be in the 270-300 mile range on the one 16 gal tank. Unless you're road tripping it alot (or it's like 700 hp) most times the dual tanks are more hassle an expense than they are worth.

In my experience on road trips, especially with a group of classics there's always one guy that needs fuel around 200-220 miles and the group is stopping anyway. That or someone needs a bathroom.

 

[SquareRoot]

What makes this different than my dual tanks, in tank pumps and pollack 6 port valve?

 

[bluex]

What makes this different than my dual tanks, in tank pumps and pollack 6 port valve?

Nothing, that's why I said: "Other people have had luck getting it to work". You're on the short list of people I know of that got it to work without problems. Idk if the valves are manufactured different, with cheaper parts or what changed.

Kinda like my sniper(s) work great, but you hate them

 

[SquareRoot]

I had a bad experience with Sniper. The Holley forum had a lot of others with issues. I realize not everyone has issues, there are bad runs of production and times change. Therefore, from now I'm making an effort to not bash the Sniper. I may slip so feel free to remind me not to be a hypocrite. I'll take my own advice and Carry On.

 

[SquareRoot]

But..... misspell axle and it's game on!

 

[SquareRoot]

Is anyone here successfully running dual Sniper EFI conversion return style tanks (pump and separate fuel sender model) with a Pollak or other brand 6 port selector valve with either PF4 or Sniper EFI ? This is my current goal but don't know if it's even possible never mind how to correctly do it !

Yes. Zero issues.

 

[SquareRoot]

Everytime I've tried it, it gives me trouble. The valves wind up failing an returning fuel to the opposite tank it's pulling from, which overflows that tank. I tell people to install a rear mounted tank from a 87 blazer. The 25 gal fits good for a shortbed an a 31 or even a 40 will work for a longbed. Just got to watch the ground clearance with a 40 on a lowered one.

There's no possible way it's pulling from one tank and returning to the other unless your lines are crossed. Not physically possible. I cut a pollack 6 port valve apart to investigate how the contacts for the gauge work. Those sliding valves can only do one or the other. I guess it's possible you got a crap Chinese knockoff (Amazon?) and the clearances are so loose that it bleeds over under pressure?

 

[Fastduramax]

Mike, did you use the EFI tank kit with the separate fuel pump and sending unit ? I see the Pollak has a max of 65psi how did you regulate the pressure before the Pollak ? How do you wire it to have one pump shut off when you switch to the other tank ? Sorry for my lack of knowledge of the inner workings of dual tanks

 

[bluex]

There's no possible way it's pulling from one tank and returning to the other unless your lines are crossed. Not physically possible. I cut a pollack 6 port valve apart to investigate how the contacts for the gauge work. Those sliding valves can only do one or the other. I guess it's possible you got a crap Chinese knockoff (Amazon?) and the clearances are so loose that it bleeds over under pressure?

I'm not sure how it happened either. Its been a couple years now so I'm not 100% sure where we sourced the valves but it was probably summit. I know the second one was a pollack for sure. The truck was an LS swap with EP381 pumps did it with 2 valves within 2-3 weeks of installing them. We deleted the valve, ran 2 corvette regulators with check valves and a y up to the motor. The check valves lasted about a month an half iirc. When it happened that time the customer decided to just ditch the pass side tank. Several other people in my local area have had issues with the valves as well at the higher pressures. Never heard of an issue like that with carb/tbi pressures. My only guess is the higher pressure causes it to not seat fully an it bleeds some return fuel off to the opposite tank. If that tank is already full it doesn't take much to overflow it.

Just my opinion for how most people use these trucks now a days it's alot of hassle an extra expense on extra parts that don't really make a huge difference in how the truck performs. I'm sure someday someone will make me try it again though because they just have to keep them no matter what I tell them....

 

[bluex]

Mike, did you use the EFI tank kit with the separate fuel pump and sending unit ? I see the Pollak has a max of 65psi how did you regulate the pressure before the Pollak ? How do you wire it to have one pump shut off when you switch to the other tank ? Sorry for my lack of knowledge of the inner workings of dual tanks

Electric fuel pumps are much more efficient at pushing fuel rather than pulling it. I've also seen people put 1 external pump after the valve an run it that way. They always live a short life in that arrangement. External pumps are loud, they don't get the benefit of fuel around them for cooling and are best gravity fed so they are not pulling the fuel. There's no real way to gravity feed them with the stock tanks and valve.

Long story short they are best done in tank for longevity and to power them you'll have to switch to an 87 style switch and wiring setup if your truck is 86 and down. I think there are diagrams somewhere around here showing the 87 wiring, I'll see if I can track them down.

With a sniper the pressure is regulated at the unit itself there's no need to regulate it before the valve.

 

[Fastduramax]

Great info Blue thank you, I opted for the PF4 XT recently that was not available at the time of my build that’s why my Sniper is in the classifieds, that said I do now need to run an external regulator and yes my truck is an 86 but did come with factory dual tanks… Perhaps AA has an 87 tank harness ? My head scratching is that wouldn’t the fuel pressure need to be regulated after the pumps but before the Pollak so the issue you had dosen’t occur ? The sniper is regulating fuel at the throttle body therefore the Pollak would be getting hit with full pump pressure is that not correct ?

 

[Fastduramax]

I do have a full set of the really cool color laminated wiring diagrams I believe covers to 87 but I’d have to confirm that….