During a rebuild I decided to rewire my fuel pumps again, and followed Cohbra's write-up here...

https://www.rx7club.com/3rd-generati...lights-998596/

I'm having no problems with that part of the system, my problems start in the stock part of the wiring.

When trying to start the car after the new rebuild, we were having issues starting it with the Adaptronic and thought maybe the injectors weren't firing or something, so I put my old PFC back in and I either got no fuel pressure right away, or it happened shortly after, I don't remember which. Either way, I jumped F/P and GND in the diagnostic box and got fuel pressure and we started the car on that and it actually ran perfectly. I troubleshot the lack of fuel pressure that time for a few days and then remembered the problem seemed to show when I put the PFC in. I swapped the Adaptronic in and I got fuel pressure again, but still haven't been able to start the car. The other night, the no fuel pressure problem came back. After troubleshooting, we've traced it to the green circuit opening relay (or fuel pump relay as it's called in the 93 manual), but I tried three different known-good green relays and none of them cured the problem.

I made this to show where I get voltage, but it doesn't show everywhere because I mainly checked the green and yellow relays.


This one shows where I understand the power to go (in red, and correct me if I'm wrong), and if I jump the green relay, where the power goes from there (in blue).


While doing the rebuild, I noticed a couple wires that got damaged by the driver's side wheel, so I'm thinking this might have something to do with my issues.



I also had some issues with slow cranking, but I got a new ignition switch and it seems to have fixed that problem. Although sometimes the problem was intermittent before, so only time will tell if it's truly fixed.

I did continuity checks on the wiring and it all seems to be good. For some reason the green relay just isn't closing and it happened out of the blue and with both ECUs. I might put in a stock ECU just to see if it'll start.

I'm really stumped as to why this is happening. Does anyone that's better with wiring have any ideas?

 

Lot of information that probably doesn't need to be here. What happens to the circuit opening relay exactly when you try to start the car. Fuel pressure doesn't matter at this stage. Are you seeing 12v at the pump?

 

Do you have your fuel pump resistor in?

If not, you need to bypass the fuel pump speed relay as that circuit is open

And yes, obviously shredded wires can be the issue and since you used a potato to take the pictures we can not identify the wire colors to give you more help.

 

Cut out the bad section of wire one at a time and solder in and heat shrink replacements. Then re-wrap the harness. Check your ride height and wheel fit so it doesn't rub through again.

 

Well I added more info because I figured maybe there would be something in there that someone would notice and get an idea of what it could be. The relay doesn't click, it just doesn't close to provide power to the resistor. So 12v doesn't even get close to the pump. It doesn't even get to the resistor.

Yes I do. I also tried jumping both the resistor and speed relay to no avail. I tried jumping just the speed relay...no luck.

Lol I took the pic with my phone, which usually takes great pics, but there was such little light it came out shitty. I can open it back up and see the wires but I want to check other options first.

I already repaired it. I figured that would fix the slow cranking problem but it didn't. I also made straps to hold the wires back from the wheels.

 

So when you turn the ign on the fuel pump does not prime?

If you jump F/P to GND then you can get it to run?

You must have a break in the wire that goes to the ECU to ground out the fuel pump relay.

 

That is correct. I get nothing unless I jump F/P to GND, or if I jump the switch in the green relay. Those are the only ways I get power to the resistor and back to the pumps.

Good call. I was wondering if it was a ground somewhere, I just wasn't sure where to look. My only thing about that is I got rid of the problem just by swapping ECUs. So unless there was a coincidence and it was another problem causing this before and it's now a broken wire, or unless it is a broken wire that sometimes SOMEHOW works, I'm still not sure. So you're talking about the L/W wire going to 1K on the ECU?

 

I have fuel pressure now, and I got the car to start. I guess I had old firmware on the ECU.

 

Got it going?! Good Good

 

Well, I got fuel pressure back and got it to start, but it dies after about 10 seconds. Elliot has been helping me, but we put the Power FC back in and got it to keep running on that, even though I have to use a jumper from F/P and GND to keep fuel pressure lol. So I'm going to see if I can copy some fuel and ignition numbers from the map on the PFC and use it on the Adaptronic and see what happens.

 

something else has GOT to be going on...... should be able to start it on the base map no prob.

 

Well, it starts OK. Not great, but OK. Even on the PFC I think it's super rich. I still have the slow cranking issue, but a buddy that's really good with electrical came by yesterday and he said he doesn't think it's an electrical issue, he thinks there is too much fuel or oil going in during cranking and making the engine kind of lock up. I still want to pull that front harness out (well, I don't WANT to lol, but I feel I need to and I'd like to relocate my fuse boxes into the rear bins), so I'll check it all when it's out.

I'm not starting it on the base map of the Adaptronic, but a modified one Elliot put on the Adaptronic forums.

 

Speed, do me a favor and open up your stock ECU. I want you to look at all of the blue resistors. See if any of them have turned brown.

I was working on a buddy's FD and had this exact problem. Was driving it back, suddenly died. Lots of turning over but no fuel pressure. Replaced the black and the green relay, fuel pump resistor and checked all the fuses. Still same problem. Only time I could get the car to run is with F/P + GND jumped. Swapped fuel pumps and still the same problem. There are tons of splices in the harness too. All wires have continuity. I found out the ECU wasn't sending 12v out to anything in the fuel system. Swapped out the ECU with another stock and then it worked. Gave the car back and a few days later the same problem came up again. It's got to be something in the wiring. I just don't know what exactly

 

Looks like this. See how it's blue in the middle but brown on the ends? Look for something like that.

 

You mean open up the Power FC? I wasn't using a stock one with these problems. Or are you just wanting me to see if that's how it's supposed to look on a good ECU?

 

I thought you were using a stock ecu when it first died.

Have you found out what it is yet?

 

Nope. I haven't used a stock ECU in years.

After I pulled the engine, I loaned the PFC to my buddy to try to get another car running. It was running alright on my car, but he said he didn't change the fuel map or anything, so I'm not sure why I can't get fuel pressure with it. I figured it's just something in the tune, or maybe that same part of this ECU fried, not sure. I have fuel pressure with the Adaptronic though.