Hello Rotary freinds ;o)

Very nice write up ! did not imagine what effect this little mod can do ! I will do it the Gadd way ;o) I just have a quick question: I would like to messure volt before and after mod, where is the best place to do that ? thank's guys.

Rene Barfred
DENMARK

 

The page isn't showing up for me. I'm trying to do this today while its nice out. Is there another link for the page?

 

^ +1

dead link

 

Dead Link
.....can we get a quick fix?!!

 

A little Note I want to add.. depending on the FP you use you may need ot run A higher fuse.. My FP on a dedicated line would blow 30 amp fuses . on 10 gauge

I spent a long time redid my wiring twice thinking it was grounding out somewhere . since the guide said to use a 20 amp I believe , depending on your FP , you may need to upgrade the fuse

 

I know this is an old thread (from 07) but I have a question. I'll be running dual walbro 255 pumps in tank and I had originally planned on wiring them up to the battery via a couple of bosch relays. After reading about the idle speed relay I would like to keep that feature with the dual pumps but my concern is... Will the increased voltage be enough to power the dual pumps or should I stick to the relays?

 

Follow this diagram, and stick a 30/40amp in-line fuse close to the battery.



-AzEKnightz

 

thanks for the reply Knights. I actually have that sitting in front of me. But my concern is the idle speed feature where is kicks down the voltage while idle and while cruising. I would like to keep that feature to prolong my dual pumps. but was wondering if this rewire mod (from the OP) would supply my pumps with enough volts to function?

 

This diagram actually "keeps" the function of the OEM system. Hence the red-white wire is your control side on the relay.

I dont see why it would not supply enough voltage as it is directly connected to the battery itself. As long as your alternator is able to keep up, it shouldnt be a problem. Make sense?

I actually have a dual 255 CJ-MS fuel pump assembly in my car. I am using a 40amp in-line fuse @ the power supply to Terminal 30 relay cable.

-AzEKnightz

 

maybe I'm confused then. I thought that the 12+ from the battery (30) was the supply and the Green wire (86) was the switch wire meaning whenever power was supplied to (86) it would close the loop and connect 30 to 87. ??? hence loosing the idle/cruising lower voltage.

I too have that same CJ-MS assembly.

 

Is there a idle/cruise low voltage setting? If there is then the above configuration will not maintain that function as the pump will get battery voltage at all times.

 

Yes, there is in fact a low volt relay. And I thought I was correct regarding the relay. So the question still remains. Will the stock 12+ wht/red wire carry enough volts to two walbro pumps with the power joint box mod?

 

My mistake. I thought you were saying the power supply cable (red wire fused) would have enough power to power up the twin 255.

So to answer your question, IF the stock wire is in good shape, I would say it will. HOWEVER, the reason why MANY are doing this mod is because there's too much of a voltage drop from that connector to the pump itself.

SO to test this wire, I'd find out where the PIN-out is @ the ECU side, disconnect the connector and apply Power there. Then, using a DVOM to check the voltage at the connector side near the fuel pump. By comparing the voltage supplied and received. You can see how much voltage drop was there.

OR, another way to test that connection is by testing the resistance from the ECU connector to the pump harness connector. The lower the resistance reading, the better it will be.

Once you figured that out, I believe stock fuel pump wire might be a 12 gauge thickness? It seem a tad smaller than my 10 gauge fuel pump wiring that I've used.

With that said, If you are using the stock wire to supply the two pumps. You should be able to determine if it is good enough.

Personally, I would rather use that wire as a control side on the relay (terminal 86/85) where I can draw full battery voltage once activated through (30/87). This way you have a constant juice of battery/alternator voltage and no voltage drop to the fuel pumps whatsoever.

p.s. What is the "power joint mod" <--- Not sure what it is.

-AzEKnightz

 

There's the fuse box under the dash and one under the hood. I think its on page 5 of this thread...there is a 12+ volt wire from the battery in the fuse box under the hood that's not being used. Basically the the power wire going to the pump has to pass through a few ignition switches and in the process the pump losses some voltage. So...by cutting the blue wire to the fuel pump relay and wiring up a fuse to the spare 12+ wire in the fuse box. You are now supplying the relay and pump with a 12+ source directly from the battery. People reported 12.x volts before the mod and 13.x after.

I guess I was hoping for an electrical engineer to chime in to tell me if the stock wire can handle two pumps.

 

I am not an engineer, but I think I've figured it out ;-) **being sarcastic**

Go HERE and check the wire gauge capacity/ampacity.

I double checked on the factory fuel pump wire, it is 12 awg.

According to the reference from wiki. 12awg wires can with-stand 20A.

go HERE for amperage draw - reference for walbro 255 pumps.

According to PRE Instructions, EACH walbro 255 pump draws a 7.5amp @ 12.5v and 8amp @ 14v.

2 x 8 = 16amp.

Stock wire 12 awg can with stand 20 amp.

Therefore to answer you question, YES the stock wire 12awg will be able to withstand 16 amps ;-).

I hope this helps, and I personally would still prefer 10awg over 12awg. Reason is because with the wires hot (powers), according to wiki the resistances (ohms/km) is almost twice as much. (12awg @ 6.336ohm, while 10awg @3.985ohm)

It is up to your own prefernce if you want to stay with 12awg or not. But then again. To do this job correct and if you want to keep stock function REPLACE THE complete 12awg red/white stock fuel pump supply wire to a 10awg wire.

-AzEKnightz

 

that's some good info Knights. I think I will end up doing the fuse box mod and then I'll run a 10 or 8 gauge wire in parallel with the current one from the relay just to be safe.

thanks for the help!

 

So what is the consensus? Is it better to do the above, or just use the empty slot in the fuse box? With the fuse box mod, is it literally just cutting one wire, fishing it through the bottom, and attaching it to the fuse? No other wiring needed?

Sorry to bump this, but I need to tackle this asap, and I am not quite clear on the best course of action.

 

Personally for me, the above mod is plenty enough since I am using the OEM power source to trigger my relay where I can get fully power from my battery.

I believe the function this mod is plenty efficient for anyone to use.

-AzEKnightz

 

Hello Rotaryfreinds,

I would do this mod to my FD, but found out the previously owner had done this mod ! the only thing I am not sure about is, the fuse still is in the fusebox under the driverside and I can understand that this fuse has to be pulled ? I can see no difference when I pull this fuse, car runs with it or without it in ! should I pull this fuse and if why ? thank's in advance.

Rene
DENMARK

 

Just leave it. The fuse is bypassed if done properly, which it sounds like it was since you tested and verified.

 

Leaving the fuse in will continue to deliver +12V to the big blue wire coming out of the harness into the FP relay box under the hood. If properly insulated, then this isn't a problem. But it is also not doing anything. I would remove the fuse under the dash.

 

If you cut the Blue wire low enough in the harness it doesn't need an extra wire spliced to it. I used the 20amp fuse from inside the car labeled fuel pump.

 

Did anyone ever back-up Dale Clark's website anywhere?
It seems like a lot of good info was lost, including this guide

 

I think some of the ClubRX stuff is out there on archive.org and the like. I had someone pull all the raw text out of the old database a while back and I should have the original pictures on my PC at home.

After the site got hacked many years ago I lost steam on it, didn't want to put all that back together. Thanks Hackers!

Dale

 

I know this is an old thread but wanted to thank everyone here. I just completed this mod with a few changes of my own and did write up on it about half way through the procedure. Here is the link to my "how to" for future reference and anyone else interested in the fuel pump rewire.

https://www.rx7club.com/3rd-generati.../#post12259301

-groovin