This was my thought as well: A faulty injector driver in the ECU itself.

 

He did... said it in the initial post

 

Whoops, missed that part

 

Please try to keep up.

 

From what OP has described of swapping ECUs and running new wires, I suspect the injectors are either damaged (or stuck open) or OP somehow has two damaged / malfunctioning ECUs.

I would unplug the injectors (so they can't get power) and check if they still leak when the fuel system is pressurized. That should help prove or disprove if they are damaged/stuck open.

While the injectors are unplugged, a test light might be an appropriate way to test the ECU and/or harness. The injectors should have 12-14 Volts supplied at one of the pins (black/yellow wires in the factory harness), and the ECU triggers the injector by very briefly connecting the other pin to ground to spray fuel. With the engine off, the ECU should not be connecting to ground at all so the test light should be dark / not lit at all. If the test light shows power and ground both being supplied to the injectors, that suggests a harness or ECU problem. Two damaged ECUs sounds rare but it's not impossible, if both ECUs were connected to a problematic wiring harness they both could have gotten zapped.

With the injector disconnected, testing with a multimeter might get some false conclusions since the trigger pin might show 0 Volts but that doesn't mean the ECU is necessarily connecting to ground. A multimeter voltage test with the injector plugged in would be accurate, but you would need to backprobe the pins and that's beyond the electrical skills of most people.

 

Whoops wrong thread.

 

I would say order a noid light from amazon or get one from a local parts store to see if the issue is signal based or mechanical (like stuck open injectors.) I would still lean on the ECU being bad since you have a new circuit and the car was running before this. The chance of multiple injectors getting mechanically stuck open are extremely rare unless you found some debris in the system after the fuel filter. There is a much high chance of two bad ECUs. Old AEM ECUs are known to do this while doing a firmware update and PowerFC is known to do this when they fail a particular way. But at least if you narrow it down to being mechanical or electrical that will help your search. Noid lights are easier to use than trying to test with a multimeter since they are designed to be used for injectors. Otherwise go get some T-pins from a craft store and back probe the injector connector so you can alligator clip the multimeter leads instead of trying to stab the connector or harness with fat leads.

 

Humour me and use your power FC commander to check the TPS ranges. The car does not need to be running.

 

You want to look at the movement for VTA1 and VTA 2 as you depress the throttle.

 

I don't believe the injectors will fire period without a crank signal unless there is a setting in PowerFC I'm not aware of. TPS or other sensor inputs shouldn't have any effect on fueling until it sees RPM. I'm guessing you aren't seeing any RPM on the display while the car is off?

 

The Power FC commander also has a "injector duty" read out.


https://youtube.com/shorts/5mEIBbUTGVk


https://youtube.com/shorts/XokgmyCl3B4

 

 

When I was testing the entire circuit, I removed power from the injectors and they did not fire. That is why I have been chasing ground issues. From what I have tested, the injectors are still good.

 

This is actually a very helpful thought because previously there was a brand new FPR installed. The old one was very hard to read, I will check this as soon as possible. Also apologies for late response I very much appreciate all the help, im going down the list catching up with posts.

 

All new injector seals were installed a couple weeks ago.

 

With Injector power completely disconnected there is no fuel leak so we know the seals are holding up fine to the rail pressure.

 

Check continuity from either pin on the unplugged injector to the rail body itself. The last thing I can think of if that passes is to remove the ground signal pin from the ecu and see if the injectors shut. If they do then the problem is either both ecus you tested OR the ground in the harness is rubber through somewhere causing a continuous ground.

These are the last 3 possibilities based on what has been said so far.

 

The PowerFC that was put in for testing purposes came out of a running FD. The seals hold up to rail pressure with injector power disconnected, the injectors have 12v and are grounded at all times otherwise(thats the issue here). Used a noid light to see if there were and pulses that were to small to be picked up by the DMM, there is just constant power unfortunatly. When the testing PowerFC was put back into the other FD it functioned correctly so I dont think either ECUs are zapped. I have also backprobed the injectors and got the same result (I am a master tech that specializes in electrical so yes its within my skillset).

 

Yeah I agree with you, maybe somewhere in the body harness has rubbed through and cause the ecu to ground out like that. But it wouldve had to be somewhere completely unrelated to the injector wiring. I did check the injector pins to the rail but I cant remeber what the outcome was so let me go check and I will also humor the TPS test aswell.

 

Did anyone fish wires through the same hole in the firewall as your harness, say to put in aftermarket gauges?

 

That's right..... even if it was rubbed through in the harness, you built that sub harness to rule that out. Another idea.... isolate where the issue COULD be. Unplug connect 4 on the ecu and see if the ground drops from the injector. This will at least tell you where the constant ground is coming from. Plug 4 on the ecu is where the pins for the injector grounds are. The power source for the injectors come from the EGI relay.

https://www.rx7club.com/3rd-generati...power-1123691/

So at best this would say the grounding issue can be isolated to SOMETHING on that connector.

 

Bent pin unlikely?

 

FPR isn't a flow solenoid. Maximum bypass flow will be either key on engine not running or warm idle depending on the voltage and pump curve.

 

Not that I follow this fully, but Mazda messed with the standard FPR set up by inserting a control solenoid into the vacuum line circuit to help with hot starts.

But in any event, it sounds almost like the OP has an aftermarket FPR installed.

 

Alright so I tested to injector pins while disconnected to the fuel rail/ground and no issues there. Going through the car again, as soon as I plug in the injectors, key completely out of the car, I can hear the injectors clicking open. And after looking further and plugging in the handheld PowerFC, it has constant power even with key off. So there is for sure a short somewhere on the power supply side of the ecu. You guys would know more about how that would affect the circuit, would the ecu being shorted to power somehow cause the injectors to ground out?