I think I can visualize that one. The Hobbs switch is the activation authority for the relay which is constantly grounded to the chassis. As the hobbs switch sees the reference boost to close the circuit, it then enacts the relay which automatically kicks on the secondary pump. That makes sense now.

Ok, what about the wiring to the secondary pump. Just drill a hole into the top of the bucket assembly and JB weld closed after the wire is taken through?? What about the ground for it?? Just run it to the ground on the sending unit assembly with the other pump?

 

Here is how he did his. The hobbs switch just switches polarity for the relay turn on.


For the switch, that I am thinking about. Does the hobbs switch work on the second pump no matter which pump is being used as the primary?

 

After some more thought, I think I'm going to give this a shot myself. A quick search on eBay turned up Walbro high pressure 255LPH pumps for about $100 each, so the relay and everything else isn't going to cost $400. Seems like it's not going to be too difficult to do.

 

Nice work atljar. The stock relay for pump 1 is wired exactly the same except its 12v turn on reference comes from the PCM instead of the hobbs switch. My custom primary/secondary switch juxtaposes the two positive reference wires that go to the 2 relays so you can switch fuel pumps.

 

So easy once you said it like that My final rendering.



The Four way switch may be a little tricky to find. It may also be called a DPDT Polarity Reverse switch. Just make sure it has 4 extermal terminals, not 6. Maybe 97WS6Pilot could share where he found his.

 

Man, you aren't kidding....I've been looking for one all morning. Still haven't come across one that meets all requirements at once.

 

My first try would be radio shack? Its not going to be something you find at autozone.

If you cant find the Polarity Reversing one...
You could buy a 6 terminal DPDT switch and wire the internal connections yourself to the external terminals. (The jumper wires inside the switch, just make the jumper connection on the outside.)

 

You guys make me sick. I wish I would've studied harder back in high school after looking at all these schematics. LOL!

 

Just a thought, but WHY the worry about equal run time on the pumps. How often does a pump actually fail. I just feel that wiring in a semi-complex setup with the polarity reversing switch isn't that necessary. Anyone else following me?

 

I think that the main purpose is to only activate the secondary pump when needed. IE...under boost or the use of another power adder. I know I'm not very concerned with equal run time.

It might be ok to run both pumps full time but I don't know for sure. Any info on this when considered with stock fuel supply lines?

 

I think you missed my point. I'm talking about the couple of people who are wiring in a switch to run pump A one day and pump B the next day, for equal run time. I just see that as nothing more than extra wiring.

On another note, if I do this myself, which walbro pumps should I use and where do I get them as Summit and Jegs don't seem to carry walbro pumps.

 

The new Walbro pump for GM is the F20000169.

Auto Performance Enginneering was previously mentioned in this thread as a good source but I have never dealt with them. Site has a good bit of info on it so I imagine its could be a good source...pumps are listed for 105 each.

 

I think you may have missed the point of this entire thing.

Wiring a pump like this will only run 1 pump at a time, UNTIL a preset boost level comes on (lets say 6 psi). Once you get 6psi of manifold pressure, the second pump will turn on.

Pump 1 will run as your primary, and Pump 2 will turn on with boost. By flipping the switch, Pump 2 will be the primary and pump 1 will turn on with boost.



Personally I think its over complex too, but i know how to do the wiring so I figured I would help out those who wanted a schematic.

If it were MY car, I would wire it like my initial diagram, and place a switch "T" into the ground between the relay and the hobbs switch. Connect the other side of the switch to ground. This would have the Primary pump always be the primary pump, and the second pump would come on with boost. If you flipped the switch both pumps would run full time.

If you dont care about boost activation, you can just remove the hobbs switch and just run the switch I mentioned above. ON/OFF only

 

I don't think I missed to point at all. Not sure what I said that led you to that conclusion. In fact when I read your first couple of sentences it seems like were saying the same thing...well at least in my head. I fully understand what the point of running both pumps is and the fact that both pumps are not on all the time. I only mentioned running both pumps as an open ended question...not a suggestion.

After reading your post I think we're both on the same page so I'll chalk it up to a miss communication by me.

For me personally, a boost reference will not work so I mentioned in a previous post that I would probably just activate the secondary pump when my nitrous master arm was on so that the additional fuel was available.

Running both pumps would be a waste on street setups like most of us have.

 

Fastbird was asking about the switch, and then you responded about the purpose just being to activate the second pump when needed. I thought you were talking about the switch, not the entire thing.

You have it, message boards can be hard to precisely communicate sometimes!

As for your concern with running two pumps full time when you really dont need the fuel...
I wouldnt worry about the fuel supply lines. I would worry about the return lines, if your regulator and return lines cant handle the extra volume, you will have a pressure spike on the entire system. The walbro pumps have a built in pressure release, but I think I remember seeing that it was in the 90psi range.