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Hey guys I could really use your help with my non-running 1993 Toyota Supra NA. I’m going to try to give you guys all the details so here we go. My supra has been down for at least three months now and has been very frustrating because I was really excited to enjoy it this summer. It first broke when I was driving and the engine started making a weird noise and the car died on the side of the road.



I first thought it was a timing belt issue because as soon as it broke we tried turning it on and it made a weird clanking noise, but we opened up the timing belt cover and saw everything intact. It wasn’t working until I started messing with the fuel pump connections in the rear of the car under hatchback and when I applied pressure to the connections the car would start. I thought everything was good and that it was just the connections so I took it for a ride and minutes later the car died again. I figured the connections were busted so I soldered the wires individually together but the car would crank, sometimes start, then it would die again. I swapped out the fuel pump but same thing would happen. I changed the fuel filter and nothing. I changed the spark plugs and nothing. I tested and changed the fuel injectors and nothing. I swapped the ECU and nothing. I swapped the fuel pressure regulator and nothing. I took it to a mechanic and he suggested to swap the ignition switch so I bought on and swapped it. When we turned it on the car was on for about 3 minutes until it died and then the car wouldn’t start again. I know it’s a fuel related issue because we sprayed starter fluid into the intake valve while starting the car and the car would start. But the fuel is getting from the fuel pump to the front of the car because we opened up the fuel pressure regulator and attempted to start the car and fuel would spill out. The fuel is just somehow not getting to the fuel injectors.



I’ve tried so many solutions but none of them seem to work. The mechanic has no idea what is going on so I’m towing the car back to my house. I was told that supras are notorious for having electrical issues specifically with resistors but how would I even know what to replace/test? Right now I could really use some help from anyone that has an idea of what is going on or knows any notorious reasons on why supras fail like this. Or if any of you know somebody that may know an answer to this please let me know.



Edit: Also when I purchased the car it had wiring issues from the battery terminals so we swapped the wires and it worked perfectly for about 5 months until this happened.



TLDR: Car was purchased broken, fixed and ran for about 5 months until it broke again. Obvious solutions did not work, possibly fuel/electrical related issue. 2 anomalies where the car did start for a short period of time. Hit a dead end on what to fix/replace now.
 

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SO, this is just a shot in the dark but It seems like you have tried everything else. my supra (93 NA) was having a similar episode months ago, It was doing all the same things as you are describing. It would run just fine after I'd throw a new part at it, I would then go test drive it around my house for a few days, eventually I would trust it and think, "Finally I fixed it!" I would then try to take it to work and at random it would kill itself....typically with no ability to restart. I ended up going to the fuel pump computer (the one located in the driver side rear quarter panel) and putting a multi-meter to the wires that take incoming voltage from the Main ECU to ultimately run the fuel pumps HI/LOW settings. I started the car and let it idle while doing the check; first I observed a steady voltage then all of a sudden NO voltage and it stalled again and wouldn't restart. Now as a disclaimer I'm not a Toyota Tech, but from what I under stand, the main ECU sends a small voltage to the Fuel pump computer (or Fuel pump ECU) and that small voltage operates a High/Low voltage signal that runs our fuel pumps, if the main ECU all of a sudden decides NOT to send that voltage to the Fuel pump computer, then the fuel pump will not run at all. So what I ended up doing was bypassing the Fuel pump computer all together and performing the 12v fuel pump mod. I ended up skipping the 12V relay step mainly because for a relay to operate it needs that small voltage from the Main ECU (which i wasn't getting) so to completely take the Main ECU and Fuel pump computer out of my fuel pumps operation, I now run my fuel pump directly off ING 12V so whenever the ignition is past ACC my fuel pump runs a constant 12V. This ended up resolving the issue, you can find the write up here. http://mkiv.com/techarticles/12v_mod/12v_mod.htm

Hope that gets you back on the road!
 
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