Today's tasks at sunrise: Fuelcell float wiring and speed sensor to ECU wiring

[s13_240_rb20]

Well, I have once again hit that day of the week that I am off of work AND somewhat free for time. As the title says, I am planning on doing some wiring work. I need to:

Wire my fuel cell's float device (for gas level) to the old fuel pump assembly's wiring (to gas gauge on dash); and

Figure out why my speedometer works, but my datascan shows only 0mph when driving. I am assuming that means that my speed sensor runs from the transmission to the dash, but NOT to the ECU?

Anyways, I am just now starting my search and opening my FSM, but I am posting this in hopes that some direct advice will save me alotttt of trial and error.

So if anyone has ANY info on these two wiring tasks, please help!!!

--TJ

[s13_240_rb20]

Ok...well, I got the fuel gauge working with my fuel cell's float, but my dash gauge works backwords...lol I'm ok with that tho...as long as I have something to look at.

But if anyone else is searching for this answer:

A fuel gauge depends on a sensor (I guess) that sends out a signal on 1 wire and gets that same signal back on another wire. However, the signal will not be the same level. Both of these wires connect onto a variable resistor, known as a potentiometer (ummm...potential...meter..lol). The float device changes the position of the potentiometer, thereby changing the resistance that the signal has to pass through before it can return to the sensor. If you can't understand by my description, then unplug your fuel pump harness and do a resistance check of the 2 wires going to the float device (potentiometer)....then manually adjust the "gas level" of the float and repeat the test. Different resistance reading, ya?? There you have it.

To hook up my dash gas gauge to the fuel cell's float, I re-routed those two wires to the center pole and the ground connection on top of the fuel cell's float device. Polarity does not seem to matter since this is not an electrical device that we are power...it is just a resister, and even when I swapped the two wires, my dash gas gauge still works backwords. Even though my fuel cell is only 10gallons, E is Full and F is bone-dry empty. I was surprised that my dash gas gauge was still "in scale".....

ANYWAYS:

I did not have time to look at my speedometer wiring on the car. Just read the FSM. I understand that my VSS is split into 2 signals, but I guess I will have to see if pin 53 is getting any voltage, and then manually trace back from there. Can anyone tell me where the VSS signal is split into the 2 signals (dash gauge & ECU)????or does anyone know if a Blitz ECU will report the speed to the datascan software?? The Blizt ECU removes limiters but I don't know how or what effects is has..

--TJ

[s13_240_rb20]

ANYWAYS:

I did not have time to look at my speedometer wiring on the car. Just read the FSM. I understand that my VSS is split into 2 signals, but I guess I will have to see if pin 53 is getting any voltage, and then manually trace back from there. Can anyone tell me where the VSS signal is split into the 2 signals (dash gauge & ECU)????or does anyone know if a Blitz ECU will report the speed to the datascan software?? The Blizt ECU removes limiters but I don't know how or what effects is has..

--TJ

WOW!!! It took me two weeks to find the time to look at a single wire...lolAnyways, two weeks later, I found the answer to making speed register in Datascan....

So if anyone else can't figure out why speed isn't reported in Datascan, here was MY answer (on a 1990 240sx hatch, with a rb20det and Blitz Access ECU ):

I checked pin 53 on the ECU and traced it back about 10 inches away from the ECU (about where my Consult connector is spliced in) and found that the wire had been cut. I am willing to bet money that I cut it at some point in time, though I don't remember doing it AND I see no evidence of a wire that matches it......did I cut it cuz it connected my ECU to the clip??....probably....anyways...

To fix this, I connected a wire to the pin 53 wire and ran it behind the dash to the back of the speedometer. On the back of my speedometer, I connected it to the screw labeled "2p" (DISCLAIMER: other models may be labeled differently). I would guess you can also splice it onto the yellow/green wire that is on the wiring harness, but I have had my tach connected to it's screw on the back for 2 years with no problem, so I just connected this to a screw also.

Anyways, hope somebody finds this useful...

--TJ