1988 rx7 na dieing and can't figure out why
 

So I got the car a while ago in a trade and I got it running but only did a couple test runs around the block cause the brakes weren't so good and the motor ran good . Didn't die , ran it out to red line . Everything was good motor related and then I got it up in the air to run new brake lines and finally got I back on the ground after a couple months and it developed a new problem . So I was driving it and the motor just died so I pulled over and turned the key off and went to start it and it started right back up and it kept doing this a lot so in my process of testing when it would die and I would leave it in gear the rim gauge would continue to read and then I went to check the battery connection so I put the clutch in to let the rim fall to zero and the battery gauge reads good and all lights stay on and if I let the clutch back out its still dead and the rim gauge continues to read rpm but the weird thing is that when it dies while I'm driving if I leave it in gear and turn the key completely off and turn it back to the on position right away it will come back to life and I did this a lot hoping the problem would go away but it didn't and when it died I could still hear the fuel pump going . So I put it in the garage cause I was done with it for that day . The next day I went to start it and it started but only went up to 1000 rpm and sounded like a bad misfire so I gave it a little gas and I got it up to 2000 rpm and then it just died and I went to start it again and it did the same thing and then it wouldn't start at all so I figured it was flooded so I left it for the day and the next day I was like what the hell and went to start it and it started right like It should so I went to drive it and it had the same issues except this time after a couple times restarting it and it dieing as I was pulling it back into my garage it wouldn't restart . I pushed it in the garage and checked for spark and I had spark . I checked to make sure fuel was getting to the engine by pulling the return fuel line off the fuel rail right next to the iinlit and went to crank the engine and it squinted out fuel so it's getting fuel too the engine . So the only thing I could think was that the primary injectors aren't firing . So what I can't think of is why when it died it would come back to life after turning the key off and right back on and it would come back to life but not if I just leave it in gear without turning the key off and back on . So does anyone know why it would do that and if it is the injectors or maybe the ecu. Any input would be appreciated

you should check the fuel pressure, your test doesn't really verify that it is building much of any pressure.

I will but I don't think the problem is fuel pressure because of how it was dying because sometimes it would die every couple seconds but then it would let me drive around the block a couple times and run thru the full rpm range so if I didn't have sufficient fuel pressure I wouldn't have been able to do that

This is what happened to me when my first fuel pump kill switch failed. The car would randomly die. I replaced it with a superior quality switch and my problem went away.

I would (with the car running, if you can) check the voltage at the pump connector on the drivers side rear shock tower. If it is inconsistent, you may have an intermittent electrical problem somewhere along the line (unlikely) or at one of the connectors. Also, if the pump is functioning properly, you should check the pressure as mentioned above.

I haven't been able to restart it but I will wire 12v straight to the pump and see if there's a difference

And you might want to check the main relay.

Where is that relay and what terminals should I ohm

The relay is located near the trailing coil (bolted to the fender) and has two plugs. Unplug the one with 4 wires and jumper B/G to B/Y and W/L to B/W and it will bypass the relay completely.

Ok and I also swapped that relay out with another one and no difference . What systems does the main relay control

It controls power to the ECU, emissions solenoids, coils and injectors. The relay has a body ground which helps activate it w/key to on. If the ground is faulty then switching units will be of no help. Bypassing the relay takes the faulty ground issue out of the equation and thus helps to eliminate it as being the issue.

Ok thanks . I'll try bypassing it and see what happens

Also does it ground thru the screw securing it to the fender cause that screw is pretty rusty

The plug w/2 wires has a ground wire (Black) for the unit to work w/key to on, so the screw is immaterial.

Well I did that and it didn't help so then after a good solid minute of cranking in intervals I pulled the spark plugs out and they are all dry which makes me think that either the injectors are clogged or the wiring going to the injectors broke which would make sense because at first it would only happen while driving but then I think about it would instantly come back to life if I turned the key off and then back on right away so what would cause the injectors to come back to life when the key is turned off then back on ? I'm gonna try wiring 12v straight to the pump to make sure it's pumping fuel to the injectors but let's say I didn't have enough pressure for it to run wouldn't the plugs still be wet with fuel and then at least try to start cause right now it's not even trying at all .or could it be the ecumenical ground and I still have good spark . Where does the ecu ground so I can try cleaning that ground ? I tried looking thru the service manual to find the ground location but can't find it in the manual . I still have to go get a fuel pressure test kit .

The ECU uses the ground on top of the engine.

W/key to on what is the voltage of the Brown/White wire at the TPS? Should read 5 volts.

I don't see a brown/white wire . There are 3 wires . Black with red stripe . Light green with red stripe and a solid orange wire

The Orange wire is likely the Brown/White wire. And you could always look at the pressure sensor for it has the Br/W wire.

https://cimg5.ibsrv.net/gimg/www.rx7...fbc92e5d6d.jpg

As i was going to test the tps wires for voltage i was moving the plug around to get a better angle and then i could hear theses relays clicking so i think the tps plug needs to be cleaned or there might be a broken wire in the loom but what do these relays have to do with the tps .

I I tested the brown white wire at the pressure sensors and it reads 4.97 v

And I tested the orange wire at the tps and it reads the same while I'm moving the plug around with the replays clicking

https://cimg3.ibsrv.net/gimg/www.rx7...ff70a9b891.jpg

https://cimg8.ibsrv.net/gimg/www.rx7...89eff62eab.jpg

https://cimg3.ibsrv.net/gimg/www.rx7...ca53cf69fa.jpg

They are emission solenoids. The TPS controls the switching (has the Blue/Red wire) and relief (has the Blue/Yellow wire) solenoids.

Well with the tps unplugged I wiggle the connecter that comes out of the loom for the tps and they still click so I think there is a problem in the loom but would this somehow be related to the injectors not firing and with how sensitive this plug is it would make sense that the problem started only happening while driving so the bouncing moved this plug around and somehow causes the injectors to stop firing ?
https://cimg8.ibsrv.net/gimg/www.rx7...e8e1a79990.jpg

You could verify if the ECU is attempting to fire the primary injectors w/key to start. At the ECU the front primary is Light Green (pin 3E) and the rear primary is Light Green/Black (pin 3C). Pin 3I (smallest plug of the ECU) of the ECU is B/W and has voltage w/key to on and start. With a LED light you place one wire of the light to pin 3I and the other wire to one of the injector wires and w/key to start the light will flicker indicating the firing of the injector.

And the ecu is under the carpet on the passenger side right ?