1979 EFI conversion-dual fuel pump wiring

[Too much]

I have a 1979 K25 and we are about to do an FiTech unit on it. I’ve purchased 87 gas tanks, 87 sending units, aeromotive in tank pumps, the 87 switching valve with its pigtail harness and the 87 switch for the dash. What relay do I use to wire the pumps so they turn on and off when each tank is selected?

 

[Frankenchevy]

Just a heads up to research... 87 switch valve was designed for 10-15 psi pumps. Efi needs approximately 60psi, so hopefully it’s up to the task. I’m not sure, just making sure you are.

I used a different switch setup altogether. However, I’d assume that the switch has a single power supply 12vdc+ that gets directed to the selected side. If that’s the case, only one relay is necessary on the hot(line) side of the switch. Then it’ll only power up the selected pump.

Otherwise, the two load sides of the switch can act as triggers for individual relays.

Sorry I can’t provide pictures. My sniper has a built in relay for the fuel pump, so I didn’t have to do any of this.

 

[Charlie]

 

[Too much]

I bought AC Delco part number U7001. it's rated for 65psi.

 

[C10MixMaster]

I have a 1979 K25 and we are about to do an FiTech unit on it. I’ve purchased 87 gas tanks, 87 sending units, aeromotive in tank pumps, the 87 switching valve with its pigtail harness and the 87 switch for the dash. What relay do I use to wire the pumps so they turn on and off when each tank is selected?

here the 87 diagram. the wiring is different than your 79. if you can get the switch and harness from the later version it will help you might have to make a custom harness. ignore the fuel module part of the diagram but the rest is accurate to your project..

You must be registered for see images attach

 

[Too much]

C10, that diagram helps lots! Thanks!

 

[4WDKC]

Just a heads up to research... 87 switch valve was designed for 10-15 psi pumps. Efi needs approximately 60psi, so hopefully it’s up to the task. I’m not sure, just making sure you are.

I used a different switch setup altogether. However, I’d assume that the switch has a single power supply 12vdc+ that gets directed to the selected side. If that’s the case, only one relay is necessary on the hot(line) side of the switch. Then it’ll only power up the selected pump.

Otherwise, the two load sides of the switch can act as triggers for individual relays.

Sorry I can’t provide pictures. My sniper has a built in relay for the fuel pump, so I didn’t have to do any of this.

I replaced mine with a newer valve and it said it was rated to 65 psi also.

welcome, I would wire the relay in the same way the 87 did so it only uses 1 relay and switches the power to the desired tank.

 

[gmachinz]

Or I have factory style conversion kits for this type of swap-with or without an OEM supplied Pollak 65 psi valve.

You must be registered for see images attach

 

[gmachinz]

I prefer to use 2 pump relays so if the event of a relay failure, you can still switch tanks and run on the other to get where you’re going.

 

[Kasey 1977 K10]

Take a look the below. Mine was for a sniper setup but it should be similar for the fitech.

https://www.gmsquarebody.com/threads/tank-replacement-for-efi.24131/page-2#post-472294

 

[4WDKC]

I prefer to use 2 pump relays so if the event of a relay failure, you can still switch tanks and run on the other to get where you’re going.

Does your kit also use an oil pressure switch like the factory setup did?

 

[gmachinz]

The non-TBI setups did not have the trigger circuit going through an oil pressure switch but I can easily add it to any kit on request.
Older trucks say...1978-older wouldn’t have the correct pinout for a switched +12V wire for the circuit and/or use a hot air choke or none at all so that cavity is unused in the bulkhead.

It’s an integration easy enough to add but wouldnt be exactly plug n play since you (the installer)would need to source either empty underhood firewall bulkhead cavities to use (2 wires) and run them from the inside section also to the relay bank which mounts near the fuse panel. I could label everything and you would just need to route them.

 

[Too much]

Take a look the below. Mine was for a sniper setup but it should be similar for the fitech.

https://www.gmsquarebody.com/threads/tank-replacement-for-efi.24131/page-2#post-472294

Kasey,

On the 4 pin dash switch does it matter which lead gets the positive and which lead gets the ground?

 

[Too much]

Gmachinz, I think you would know the answer to my switch question as well.

 

[Kasey 1977 K10]

Kasey,

On the 4 pin dash switch does it matter which lead gets the positive and which lead gets the ground?

Take a look a the image toward the bottom of the below post. One note, I used power from my sniper efi to power the switch so that if my key is on the pumps aren't running constantly if the engine isn't running. Only during prime.

http://www.barthmobile.com/eve/forums/a/tpc/f/3431087061/m/4303955787