pics of my overkill fuel pump rewire
 

Alright so I decided I wanted to rewire my fuel pump on my 88 T2. The previous owner had rewired it to relocate the fuel pump resistor relay, as most people do. Well the car has been leaning out despite having more than enough injectors and fuel pump. I had tried testing voltage before and I was getting some low numbers for whatever reason (bad resistor relay? high resistance connections? who knows). So I figured I was just going to go all-out on my rewire and cut out the resistor relay altogether.

I also decided I didn't want any of the original wiring to go to the pump at all (Except the fuel level sender wires). Corroded 16 gauge (14 gauge?) wire just isn't going to do it for a potential 400rwhp car. I have a Supra TT pump and I want it to flow as much current as possible without heating up. I may run a Kenne Belle Boost-a-Pump sometime in the future, which is pretty tough on pumps, so that's another reason I need good current flow.

So, starting from a writeup like this: http://www.1300cc.com/howto/how2/rewire.htm

I modified this diagram a little:

http://www.1300cc.com/rx7pics/rewire/rewire1.jpg

essentially became (excuse the crappy pic)

https://www.rx7club.com/attachment.p...1&d=1203785516

pretty much bypassed the stock resistor relay and made it similar to a nonturbo series 4 car, but I'm pretty sure you need to have those 4 wires jumpered together on the resistor relay harness for this to work right. Now, I'm not sure how many people actually run new wires all the way into the gas tank. I think a lot of people just run a new wire and then solder it into the stock connection at the top of the fuel pump assembly. I have never seen any specific info on running the wires all the way into the tank, so , so myself and a good friend took on the task.

The tricky thing is getting those wires in there without leaking fumes.

https://www.rx7club.com/attachment.p...1&d=1203786449

after looking at the fuel pump assembly for a little bit, there is really only one area where you can drill a hole that won't interfere with the original wiring or the gasket mating surface. That's near the mazda logo part. So we drilled two 1/4" holes (yeah that one in the pic isn't pretty. we cleaned it up after that). That was the perfect size for the Phoenix Gold 8 gauge wire we used. The fitment was tight and it barely slid through the holes, which means a small chance of any fumes escaping.

We had to go to autozone and look around for a while to find the correct ring and spade terminals that would fit the wire properly and connect onto the pump and relay correctly. You don't want to buy the wrong terminals and then hack up the wire to make everything fit. That defeats the purpose. Also, note that my Denso Supra TT pump connects differently than a Walbro I think. I think the Walbro has one electrical connector while the Supra pump has two separate terminals for power and ground that need spade connectors.

https://www.rx7club.com/attachment.p...1&d=1203786449

https://www.rx7club.com/attachment.p...1&d=1203786449

So we put silicone sealant where the wires ran into the tank, then put those wires through the grommet and ran them to where they needed to go. The ground wire went to a bolt hole back there that was very thoroughly cleaned with a wire brush attachment on a drill. The positive wire went to the relay, which should go like this:

87: wire directly from the battery, fused
30: wire from the relay to positive lead on the pump, in the tank
86: blue wire from the original fuel pump harness. (it is black/white on the pump side of the connector though, at least on my 88 car). this triggers the relay.
85: chassis ground for the relay itself


Results: straight battery voltage at the pump, not only bypassing the resistor relay but also ALL of the 20 year old wiring. I have an aeromotive adjustable FPR and a standalone so I'm not that worried about the car running too rich off boost after I make some adjustments. In fact, this mod immediately raised my base fuel pressure 3 psi, which I compensated for by adjusting the FPR.

Removing the resistor relay may not be a good idea if you have the stock fuel pressure regulator (and probably the stock ECU as well). It'll probably just make the car run too rich, have starting problems, etc. But replacing all the factory wiring to the pump may be helpful when you are in the process of relocating the resistor relay, although you don't need to be rediculous about it and do 8 gauge like I did. 12, maybe 10 gauge should be fine. If you drill a hole be careful about getting metal shavings into the gas tank or drilling into something you shouldn't be drilling into.

now that's hardcore wiring for a fuel pump ;D nice

Looks good...

However, 8 gauge is massive overkill to the extreme amount. 8 gauge is more suited to connect the alternator output to the electrical system.

12 gauge is more then sufficient for any reasonable fuel pump.

Also, don't expect that little dab of silicon sealant to last very long. Fuel will turn it into a strange jelly like substance and it will droop into the tank.

Fuel will also eventually wick up the wire.

In addition, the yellow plastic covers on the ring terminals will dissolve in fuel, as will the wire insulation eventually as this wire is not rated for in tank use.

If you have a "potential 400rwhp car", then you should have an aftermarket EMS, which makes the 2-speed pump system redundant anyway...

First of all, gasoline is going to eat through your silicone seal and the wire insulation of that Phoenix Gold cable.
That makes for a very dangerous situation!

You need to find wire that uses insulation that is made to resist gasoline (Teflon?).

Second, when you're passing wires though metal like that, use this thing called a "bulkhead connector".
It's basically a big stud with two nuts on each end.
This is the proper way of running an electrical connection through a wall.


-Ted

As mention above, that insulated wire will melt its insulation in a mater of days/weeks and you will be left with a gas tank on fire. Which isn't what you want, I'm sure. If your going to rewire it, you should use UL-1332 electrical wire. Look for Fluororesin insulated wires, as they are gas and oil resistant.

I sure hope your not driving around with this setup. If so, stop now before its to late.

well shit. I guess I just need to change the wire in the fuel tank, everything else is fine though.

thanks for the heads up. I am going to order some UL 1332 wire and remove anything that will be dissolved by the gasoline.

ok I thought about this for a little bit and here's what I don't get. A previous owner had some regular old radio shack wire (it was smaller gauge of course) in the fuel tank when he installed a Walbro, and the wire had absolutely no problems, and that was at least three years ago. So what makes this wire different? I'm just wondering. Is it because it was designed for amplifiers?

You are saying the gasoline will chemically dissolve the insulation? Or somehow actual heat will melt it? How hot could it possibly get at the back of the car? I noticed that the fuel gauge floater thingie appears to have exposed copper on it and it never has any problems of starting a fire or anything, but of course there is hardly any amperage flowing through that.

I guess I'm just trying to understand the physical reason why there is a problem with this wire when the other radio shack wire in there never had any problems. I saw no signs of corrosion at all. Even the dab of silicone I put on there is not in the tank in any way. It is on the outer edge of the wire before the wire enters the tank.

I wondered the same thing when I read this.

Some wire may be more resistant to fuel, but regular thermoplastic wire (99% of what's on the market) won't stand up to immersion.

The fuel will dissolve the insulation.

While heat is not the issue regarding the wiring, you would be surprised how hot the fuel tank gets. Remember that the fuel circulates around the top of the hot engine. It picks up quite a bit of heat.

The fuel sender wires are actually very thinly insulated. The sender itself has an open element coil of copper wire, and the low fuel light is electrically triggered by that little float like thing with the tail coming out of it. Having exposed wiring in the fuel tank is not a huge deal. In fact the brushes in the fuel pump create quite a spark show!

The best solution is the appropriate wire and and some bulkhead connectors. You can get all of this from FuelSafe.

i wondered this same thing as well and as a test a few years ago i took a pop bottle (a plastic one at that) filled it with gas and some pre mix. in the bottle i put a few snippits of wire some verious connectors and some zip ties.
i left them in there for over a month and they were fine.

i am not saying that your speaker wire will hold up or that it is the safest wire to use, but imo most plastics are allot more resistant to gas then people think.
i would also have to say that speaker wire is designed to be run through your car and especialy your engine bay, where oil and gas are present.

Three phase ac booster pumps/transfer pumps in aircraft don't use wire as large as what your going to use. Just FYI.

Wire the same gauge as Mazda used in the original config is more than adequate.

so what your saying is to just remove the resistor relay if your going over 375rwhp?

id like to know and have reasoning to prove that before i rewire all mine and could save some time and money?:icon_tup:

I just installed a walbro and soldered connection and wrapped them in electrical tape. I guess I better redo or something.

I don't think there's a hard and fast threshold where the resistor relay is "unnecessary." I was not pleased with the job a previous owner had done with relocating the resistor relay (poor solder joints mostly) so I decided to remove it because its driveability benefits are not needed with a standalone and adjustable FPR. On a lot of other cars (not rx-7's) people just cut the damn thing out. The main reason to keep it is because it could affect gas mileage and starting on the stock ECU (although s4 n/a cars don't have it. but nobody puts a really big fuel system on there either)--and who runs the stock ECU over say 320rwhp on our cars? I see you have an Rtek from your sig. I know the new 2.1 allows you to adjust cold starts and idle mixtures, although I'm not sure how well it works. You could probably just cut the resistor relay out and if you had any problems, make some adjustments on the Rtek. Adjustable FPR would help too.

One of the reasons why I went to bigger than stock gauge wire (and once again, 8 gauge wasn't necessary, i just did it for the hell of it) is because I plan to run a Kenne Belle Boost-a-Pump should I max out the Supra TT pump on race gas. I've seen those things fry stock wiring and blow 30 amp fuses if you crank them way up because they got so hot when you run say 16-17 volts through them. This is on 500-600 whp piston engines, which is probably the fuel flow for like 400 on a rotary.

I know this goes against conventional wisdom around here, but I think people unnecessarily go to dual fuel pumps on our cars a lot of times. A supra TT pump can flow a shitload fuel if you put a kenne belle boost-a-pump on it. This pump in my car right now originally came out of an 11 second Supra TT, then my friend bought it and put it in his 10 second Vr-4, and then I bought it from him because he needs to go dual fuel pumps on his build.

That's because as you pointed out they are AC pumps. If they were DC pumps it would be a different matter.

When making any kind of power, the car will be running on a full standalone. This means the stock relay is no longer necessary. The standalone will have a single relay to power the pump and because it's fully tunable there is no need to lower the voltage to the pump at light load.

Power has nothing to do with why the system is there. The pump's 2-speed system is to increase pump life by running it slower when the engine load is low, and running it at full speed when the load is high. The stock ECU takes this into consideration when calculating fuelling. If you simply disable this system, the engine will run slightly richer at the times when it should be at load speed, but no different at other times. So if you have a stock ECU, the system should be kept and incorporated into the rewire. When the stock ECU is replaced with an aftermarket one, the 2-speed system is removed and the pump is wired up as per the instructions (although it could be used if you really wanted).

question why do anything to the fuel pump?

that is some immence hardcore wiring, might be a little excessive:icon_tup:

Read the link in the first post, it explains everything.

took it for a spin today. This made a huge difference... a map that was making the car run about 12.8:1 (obviously too lean) and refused to richen up now ran about 9.8:1 on the LC-1. I had to lean it out significantly.

I'm not sure if this is indicative of a poor rewire beforehand or indicative of the effectiveness of what I just did.

Wow, impressive results. Good thing you got that taken care of... :eek::bigthumb:

what up erikseven how ya been? got any housing porting templates?
i am in need

For anyone who was wondering... I still have that 8 gauge Phoenix Gold wire in there and my car hasn't burned to the ground. I put a little black RTV around the holes and haven't had any leaks. The wire has seen a lot of leaded fuel actually.

Oh and my buddy who originally helped me with this install had to one-up me and ran 4 gauge to the pump in his GMC Syclone setup.