EFI Dual Tank Conversion, need help on power 4 the pumps.

[SquareRoot]

@SquareRoot what part number tanks did you get?

GM1C. Rockauto.

 

[SquareRoot]

So, staring at the wiring schematic for awhile I realized something that changes things.

1. With the Pro-flo EFI it uses a NEGATIVE, ground input to power the pumps on/off. No problem, use a relay.
2. Everybody that has said to use a dedicated power source (vs tapping into the 87 sender power wires) must not realize, as did I, that the power feed first runs thru the dash mounted selector switch when using dual tanks. That would require another two relays. Not a fan of three relays to get this to work.

My research says that stock TBI pumps pull about 5 amps. That's thru the selector switch which is fed by a 16 guage wire. The , 381 pumps pull 6 amps so I'm satisfied they will be fine without relays and dedicated power source. If it blows the factory fuse I'll reconsider.

Benefit of the EFI is it uses the rpm input signal to activate the pump on circuit. No signal, no power to the pump. Plus, it primes the pumps when the key is switched on. No need for oil pressure switches or timers.

 

[Dleslie212]

So, staring at the wiring schematic for awhile I realized something that changes things.

1. With the Pro-flo EFI it uses a NEGATIVE, ground input to power the pumps on/off. No problem, use a relay.
2. Everybody that has said to use a dedicated power source (vs tapping into the 87 sender power wires) must not realize, as did I, that the power feed first runs thru the dash mounted selector switch when using dual tanks. That would require another two relays. Not a fan of three relays to get this to work.

My research says that stock TBI pumps pull about 5 amps. That's thru the selector switch which is fed by a 16 guage wire. The , 381 pumps pull 6 amps so I'm satisfied they will be fine without relays and dedicated power source. If it blows the factory fuse I'll reconsider.

Benefit of the EFI is it uses the rpm input signal to activate the pump on circuit. No signal, no power to the pump. Plus, it primes the pumps when the key is switched on. No need for oil pressure switches or timers.

So how did you end up wiring this up? I installed a Pro Flo 4 system last year and have been running on a single, external pump since then, butthats just not cutting it. Yesterday I bit the bullet and ordered two new tanks, pumps, senders and sets of mounting brackets and straps from Tanks, Inc. They won’t be here for a few weeks, but I need to start thinking about wiring. Did you end up just end up connecting to the pump power feed off of the Pro Flo system?

 

[SquareRoot]

So how did you end up wiring this up? I installed a Pro Flo 4 system last year and have been running on a single, external pump since then, butthats just not cutting it. Yesterday I bit the bullet and ordered two new tanks, pumps, senders and sets of mounting brackets and straps from Tanks, Inc. They won’t be here for a few weeks, but I need to start thinking about wiring. Did you end up just end up connecting to the pump power feed off of the Pro Flo system?

Actually I'm doing the install today. I have a wirng diagram I will post here shortly.

 

[Bextreme04]

I would still recommend doing this with relays. You would need two relays for dual tanks. Use one relay for on/off power to the second relay. Second relay should have the power from the 87 terminal on the first relay to the 30 terminal on the second relay. Run one pump power wire from the 87 terminal on the second relay and the second pump from the 87a terminal. Wire the second relay to get activated by the power output from the switch. Wire the ground from the first relay to the ECU.

If you don't have them running straight from the battery through relays, you can induce some pretty nasty EMI into the rest of the system and you can have some weird electrical issues.

 

[Dleslie212]

Actually I'm doing the install today. I have a wirng diagram I will post here shortly.

Perfect timing lol... please do. In the mean time, I’ll have to learn to read an electrical diagram

 

[Dleslie212]

I would still recommend doing this with relays. You would need two relays for dual tanks. Use one relay for on/off power to the second relay. Second relay should have the power from the 87 terminal on the first relay to the 30 terminal on the second relay. Run one pump power wire from the 87 terminal on the second relay and the second pump from the 87a terminal. Wire the second relay to get activated by the power output from the switch. Wire the ground from the first relay to the ECU.

If you don't have them running straight from the battery through relays, you can induce some pretty nasty EMI into the rest of the system and you can have some weird electrical issues.

I don’t know much about electrical... I don’t know what any of this even means

 

[Dleslie212]

Got my new tanks, straps, brackets and everything else. I’m going to take a stab at wiring this weekend I think

 

[SquareRoot]

Got my new tanks, straps, brackets and everything else. I’m going to take a stab at wiring this weekend I think

Sweet. I have spent the past few weeks converting mine over. Hit a few unexpected snags because I didn't know what I needed until I started taking things apart. I plan to have mine completed (less the P/S tank) this weekend. The last two fittings are scheduled to arrive today.

My first question is, do you have dual tanks?
What year truck?
Carb, EFI or ?

I can help you out as this is all fresh in my mind.

EDIT: I see your earlier post and that you are using the PF-4 like me. Awesome. I have a wiring diagram for that but its at home. I will sketch it out and post it. In short, the negative fuel pump output from the EFI will go to a on-off-on switch (location of your choosing) that switches the power wire (hot side) from the left to right tank. The off position doubles as a anti-theft device as it kills power to both tanks. You will need two Bosch style relays. Its very simple and reliable. The rest of the wiring (6-way valve, sending unit, gauge, etc.) will remain as is from the factory.

You will need to replace all the pieces of fuel hose with new stuff rated for high pressure (1/4",5"16, 3'8th). The 5/16th was a PITA to find locally.

You need a high pressure fuel filter.
What are you using for a regulator? Mounting locations for these can be tricky as the factory hard lines are difficult to access to make connections. It took me a few days to figure out the best way for my setup as I wanted easy access and kept away from exhaust/engine heat.

Do have headers and/or dual exhaust?

 

[SquareRoot]

Here you go.

 

[Dleslie212]

Thanks for the info!

1977 K10 with dual tanks
Using the PF4 system like you said. Headers with dual exhaust out the back. My pressure regulator is mounted right at the passenger side fuel rail - I used a 90 degree AN-6 fitting right off the fuel rail and then installed the regulator directly onto that

Do you happen to have a part number for those Bosch style relays?

Edited to add -

I redid all my fuel lines already when I installed the PF system last year. So I have new braided line going from pump to regulator, and new rubber fuel injection line going from return to six port valve already, as well as high pressure filters on inlet of regulator. My old steel factory lines have been abandoned and aren’t in use anymore

 

[SquareRoot]

Thanks for the info!

1977 K10 with dual tanks
Using the PF4 system like you said. Headers with dual exhaust out the back. My pressure regulator is mounted right at the passenger side fuel rail - I used a 90 degree AN-6 fitting right off the fuel rail and then installed the regulator directly onto that

Do you happen to have a part number for those Bosch style relays?

Edited to add -

I redid all my fuel lines already when I installed the PF system last year. So I have new braided line going from pump to regulator, and new rubber fuel injection line going from return to six port valve already, as well as high pressure filters on inlet of regulator. My old steel factory lines have been abandoned and aren’t in use anymore

 

[Dleslie212]

Cool, thanks again. I just finished getting the new tanks set up with the senders and pumps. I bought everything from Tanks, Inc. One of the reps there helped me over the phone, and recommended which pumps and senders to buy. The new tanks look almost identical to the factory tanks. The finish is really nice - I'm not sure what it is, but it looks like a gray, epoxy paint or something like that. Dimensions, shape, everything is the same other than the extra holes for the pump, sender and fill spout. Internally, theres a nice tray to keep the fuel from sloshing too much

They are ready for install now, along with new filler neck and vent hoses from LMC Truck. I thought my new brackets and straps from Brothers had come in, but I was wrong. I have to get ahold of them and figure out where the hell they are. Fingers crossed they come in before the weekend - I'd like to get started on the wiring!

Here are a few pics for anybody curious

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[SquareRoot]

Not wanting to mess with this anytime soon, I ran new wires front to rear and replaced the 40 year old loom. I included new wiring for a seven pin trailer connector as well. Bought a weather pack terminal kit and did it right. I absolutely love how easy and functional those weather pack connections are.

 

[Dleslie212]

You used the weather packs for the trailer wiring? Or for the fuel pump wiring?