Where did you find this? I'm looking in the 1993 FSM and page F-30 is different

 

I did a bunch of multimeter testing today. The highlighted paths have been tested and work as intended. So either there's a short between the ecu and the circuit opening relay (I'll test this in the morning once I identify the pin), the ecu is bad or what I think is most likely, something is telling the ECU not to activate (ground) the circuit relay.

 

Yes the relay is looking for the ground that the ECU provides. The relay is getting power, it needs the ground from the ECU. The question now is, why am I not getting a ground signal from the ECU.

 

Maybe that ground wire near the ecu is not connected? We found we had left it loose, with the result is my A/C was not working, but everything else was fine.

Did you check along the length of your front harness? My concern is that long circuit that runs through it to the resistor and back. But I guess you have tested those circuits.

 

Not sure where I got this downloaded from 9 years ago, but it has some great detail and explanations more that the USDM FSM.

 

yeah I ended up finding it, I didn’t know the service highlights book had such nice pictures, I’ve pretty much always just used the FSM

 

I suppose you have checked for bent pins on the ECU.

A more desperate thing is to open up the ecu and see if the circuit board is showing any distress.

Usually they look pretty pristine, even after 25 years.

 

I’m pretty sure it’s connected but I’ll double check tomorrow. Maybe it has gotten loose. When you say the front harness do you mean the wires that pass through the fuel relay? The fuel relay opens but there’s no power on either side unless I bridge F/P. But I tested for continuity from the F/P relay to the circuit relay that sends it power and it tested good.

 

The JDM FSM (1991-11WM4002) seems to have much more explanation and diagrams. Also there is a "New Model Introduction" 1991-11NM4002, that seems to have some unique perspectives.

I also have seen a three volume "service highlights" in English but it is lost somewhere on my hard drive.

 

I’ve never unplugged my ecu before actually. But i did move the engine harness that comes out of the firewall around a bit. I was missing the P clamp so it was hanging low and I added one from Home Depot. I’ll have to inspect the ecu and its connections tomorrow. I might have to test the harness as well, hopefully I can find out what pins go to what on the engine harness.

 

with all this hair pulling and going in and outside to look at the car and then back at the FSM I’m about to bite the bullet order a hard copy. Right now I just use the pdfs on wright here. The service highlights one seems more rare and expensive

 

The resister is bolted to the RHS of the firewall. The wires to it have to run all the way around through the front harness from the circuit opening relay on the LHS of the engine bay, then back through the front harness and a number of other harness to get to the fuel pump. The front harness hangs above the front wheels on both sides, and often gets damaged if the car is sitting too low and the fender liners get worn through. I have seen some horrendous damage to the front harness. The front harness is a monster and once water gets inside you are going to have all kinds of issues.

 

Here is a very recent example of someone local with a front harness chewed up by his front tires. The repair job is impressive, but we will who knows how much moisture got in there.

 

I did have an issue with this once where whatever was holding the harness up in the wheel well broke and the harness was rubbing on the tire but it was making a noise so I pulled over quick and zip tied it up away from the tire. It only cut through the loom around of the wires and all the insulation was intact but I will check in this tomorrow. I need to get in there and add some new loom anyways. But the signal definitely gets through the harness to the front relay and back.

 

Here is a pic of an FD being dismantled in Japan. You can see the front harness running above the wheel. It is the same on the other side. I think this may be an example of where the front harness may have been tucked up to avoid the wheel. In any event, the fender liner is not much of a defense against a tire churning away below on a radically lowered car.

 

What happens I wonder if you unplug the resistor?

 

Yeah that’s the one. I’m not super low to the ground but I am lowered and on 18s so the gap between the tire and wheel well isn’t much. And I don’t have a fender liner on at the moment on that side because it was rubbing. I’m planning to modify it.

 

The resistor should be irrelevant in this case. Power definitely passed through it I tested it. With the fuel pump relay removed I tested the pins and I got power on both sides when F/P was grounded. So power from the resistor side and then the power that would have put the pump into the higher voltage.

 

I am not sure the engine harness is involved. The front harness runs through the firewall near the ecu. I have seen damage to the harness when people shove some after market wiring through the same ports.

Mind that what most people call the "engine" harness is referred to as the "emissions" (EM) harness in the USDM wiring manual. Such manual call the starter harness the "engine harness" (E).

Note that after version 1 cars there was some changes to the wiring layout..

 

There may be a power reading but I wonder if the signal is weakened by a short, if the ecu gets unhappy.

 

It seems you narrowed it down to either a shorted wire from ecu or ecu itself. Here is a related thread, might be useful.
https://www.rx7club.com/3rd-generati...t-ecu-1113408/

Maybe reconnect back that airbag plug? Just an idea

 

I may be thinking the emissions harness. I’m thinking of the one that passes through behind the ABS module and goes to the solenoids under the UIM. My harness is brittle from the heat so I try not to mess with it too much but it’s possible I created a short when I installed the p clamp.

 

The front harness symbol is (F) and you can see most of the F/P related wiring is running through the (F) harness. (Also the rear (R) and fuel pump (FP) harnesses. Fuel pump relay is connected to the "1K" pin in the ECU (provided you have the correct wiring diagram).

 

I reconnected the airbag computer but I didn’t reconnect the airbag itself. That thing scares me.

 

I’ll look into this 1k pin tomorrow but I think that one is actually functioning. I believe the fuel relay opens even when F/P isn’t grounded but I will double check tomorrow.