i have been deliquent in posting a new, simpler solution for a rewire that maintains the low voltage operating mode. its so simple that i'm surprised that no one beat me to it. this simple solution is to run the standard hardwire but with two differences:

1) rather than cut the factory power wire at the fuel pump plug, splice the hardwire into it.

2) activate the rewire using a hobbs switch.

there are a couple of options for failsafes.

A) use the hobbs switch and a power relay to control when the rewire gets power. this is the safer option, but it requires tying the power relay into ign on/off signal other than the standard method of hardwires were it is tied to the fuel pump power wire. the way to do it is to move the power relay under the dash where its easy to pull an ign on/off signal from the fuse panel using an add-a-fuse.

B) live dangerously by using just the hobbs switch. this simplifies the rewire and removes a small voltage drop caused by the power relay, however if the hobbs switch blows chunks in the closed circuit condition, the only way to turn off the fuel pump would be to pull the rewire at the battery or pump.

the parts needed for this consist of a standard hardwire kit (i like the stm kit), a good hobbs switch, and a nice wire splice. i recommend spoolin' up for the latter two items. matt has a big batch of very nice hobbs switches that he recently bought for his new cdi ignition kit.

EDIT: Here is a very high quality Hobbs Switch sold by SpoolinUp:

http://www.spoolinup.com/Hobbs-Switch_p_83.html

 

To keep it safe you can always use a fuse block with a high amperage contactor/ relay to control everything. I put a 12 output 100amp fuse panel and use that to power all kinds of guages and stuff as well as 2 circuits for the pumps. This particular fuse/ distribution block will handle 30 amps per channel and 100amps max for the whole block.
Some people might need something to handle more amperage but for my application I am pretty sure 30amps for each pump will be more than enough. I used a 100amp contactor hardwired to the battery with an inline 100amp fuse using the ignition circuit as the trigger. This way no matter what all outputs loose power no matter what when the ignition is turned off. If you go this route make sure you use the proper guage wire and fuses in correct locations to prevent any issues.

The one I used is sold by Mcmaster Carr and is product #5183T12. It also has a cover that secures on the top to make sure nothing contacts the terminals or fuses.

Doing it this way is a little more work in the beginning but after it is all setup adding anything is very easy cause all you have to do is run your + line to the fuse block and put on a connector and land it and install the right size fuse. Then you have multiple outputs that can be used without having to route everything through the engine compartment every time. And it is a much cleaner installation and it keeps everything safe.

I currently have the fuel pump wires coming from the fuse block to the relays controlled by the OEM fuel pump circuit. I thionk I am going to change this as I already have the ignition circuit controlling the power end of things, the relay doesn't seem necessary at this point. This would make starting easier as I wouldn't have to crank the car for a second to get the pumps to kick on and pressurize everything before I actually start the car. But the pumps would kick on everytime I turn on the ignition circuit.

I have to complete a few things after my car gets finished up. One of the things I think I am going to do is wire LEDs so I can tell when each pump is on/off. Just for verification and to make diagnosing any issues easier.

The wiring that comes with the Squash Performance Double Pumper is very stout and they use high quality conectors and relays with no splices, everything is going directly to each connector which are also rated for the correct amperage. If you are looking at buying the Squash unit I would suggest paying the extra money for the wiring and relays.

 

?? This thread is meant to be about getting the best voltage to single pump setups without giving up the low voltage mode. Nothing to do with double pumpers.

 

Oh, I guess I got lost in what I was doing...LOL

My point was you can do it in different ways to create a safe setup. One way being how I did it but applied to one pump instead of 2.
Just throwing that out there as another way to skin the cat

 

 

Mine seems to functioning great! Since I also relocated all the stock relays and resistors to the trunk, I can hear the stock relay switching voltage quite a bit. And its basically anything with your foot on the gas during cruise is high voltage. NOW I know why its been a pain to get that transition tuned well, forcing open loop.

Thanks again mrfred. Although I didnt use your exact setup, it certainly helped me get my head wrapped around what I needed to do to make it work with almost all stock components.

Does anyone have the transition table for 9653?

edit: nevermind...found it.
https://www.evolutionm.net/forums/9890560-post6.html

thanks again!

 

Maybe I missed it in the thread somewhere, but why could I not do what I sketched in the attached? I haven't looked to see if I have enough access to the wire I want to cut, but it is shown as two separate connector ports... I assume there should be a little length of wire there. Then just run the rest of the STM rewire in parallel to the stock wire.

I feel like I'm missing something obvious... help me find it

 

Should work, but I think you'll be challenged to find the wire coming off relay #3. Did you see post #121?

 

Yeah, but this would be even simpler. No hobbs required. All the factory functionality.

 

Now that I look at it again, someone else tried this, and it does have an important issue. Since relay #3 is normally closed, it is possible for this configuration to result in a selfperpetuating mode when the engine is turned off. The 12 V power feeding the pump goes backwards through the power resistor, through the normally close relay, and holds your added relay open, causing the fuel pump to continue running even with the engine turned off. At least one person had this happen to them. In this situation, the voltage reaching your relay would be fairly low, about 10 V which is typically on the lower limit of what it takes to activate an automotive style relay. If you added a resistor in-series with your relay, this might drop the voltage low enough to prevent this from happening. Might also affect the speed of the relay though.

 

Sounds like an easy fix with a diode. Just need to get a 30amp 12V+ rated one and put it in the stock wire before the STM wire ties in to the pump.

 

Has anyone killed a relay yet? Or did everyone that did a varation of this mod go solid state?

 

That would fix it.

I'm using high quality automotive relays. No issues yet, and I've popped mine open for examination a few times. SSRs are more consistent in the long run but are more expensive and can have a larger voltage drop associated with them. I think the cheapest one I could find that I was willing to run was a Crydom D1D60 which costs about $110.

 

Attachment in post 120 has been working well for me for a year. I can hear it click since its in the trunk and works as expected.

 

FYI: SpoolinUp now sells a very nice high quality Hobbs switch.

http://www.spoolinup.com/Hobbs-Switch_p_83.html