Genshie

Hey All,

YT has been an incredible resource for the 3.4 swap into my 85 4Runner rockcrawler. And for the past couple months, I've just searched and searched and read threads over and over. And now I'm almost across the finish line, but can't quite get there. This issue is stumping me, so I'm hoping someone might uncover something I haven't.

Motor is out of a 99 4Runner 4x4 Auto. Engine will crank and turn over, but dies immediately after turning over. I have fuel (the whole garage stinks after several attempts), and I have spark (initially), but as soon as the ignition goes from start to on, it dies. If I try to restart immediately, there's no spark. If I wait, I get spark again, but then it dies the same way. Checked OBDII for codes, no codes.

I've got 12v to all the essential components (igniter, coils, AFM, etc). I also have signal to and from igniter, so igniter is good. Igniter is grounded well. I have engine and body and frame grounds. Camshaft and crankshaft sensors also are sending signals, so those are good. Everything under the hood seems fine. Which leads me to my wiring.

B+, BATT, STP, SIL are all hooked up correctly. FC is hooked up to the COR. I didn't have IGSW hooked up, but I hooked it up and it still doesn't work.

The only thing I can think of which might be the problem is my neutral safety switch. I have the wire from the starter to the STA on the ECU, and from the ECU to the neutral safety switch. I also put the starter wire from the ignition into the circuit. NSW wire goes to ECU from the neutral switch as it should.

My 85 never had a starter relay, but the 99 did. When I look at the wiring diagram, power is coming from the IGN fuse to the NSW pin on the ECU, then out the STA pin to the starter relay. I don't have it wired this way, and as a result, the engine will crank in PRND2 and 1. But it shouldn't be able to do that. This is the only thing amiss which I can imagine might be killing my spark, but why would I have spark in the START position, but not in RUN? Further, why does the engine 'time out', not giving me spark immediately after?

Am I chasing after the wrong thing? Is there something else I might be missing? I tried grounding the ECU to the body, but that doesn't work either.

Thanks for any ideas or feedback!

Kurt G.

dntsdad

Maybe I am reading this wrong but power (or ground) doesnt come FROM the STA pin. It goes TO it to tell the ECM the motor is starting.

I think that you have a wiring issue but not sure what. I would redouble check everything but I assume you have already. Could also be your MAF. Is it backwards?

Try this.
https://www.yotatech.com/forums/f160...n-dies-184100/

Genshie

Yeah, I also agree its a wiring issue besides the starter. Since my '85 didn't have a relay, I fed the ST1 wire (b-w) into the STA circuit, but like you mentioned dntsdad, 12v should be coming from the NSW side, so I'm assuming I need to feed my ST1 wire into the NSW circuit. I rewired, but still the same situation.

I also tried continually cranking after the engine turned over to see if I kept getting spark, but spark cut out. So the engine turns over, dies, and the starter keeps running, but with no spark. So it isn't a RUN versus START wiring issue. Spark is cutting out regardless. So, what could cause a cut in spark after getting enough spark to turn the engine over? Once the engine turns over, is there a circuit that closes to continue giving spark I don't have connected?

I am an electrical imbecile.

Thanks for any help!

Genshie

Figured it out. It was exactly what I assumed - something simple. I went over the wiring diagram numerous times, and after verifying everything on the engine was getting 12V, I turned to the grounds. Well, the wiring harness I have is out of a '99 4Runner Limited, which had the security system with immobilizer. My ECU is out of a 2000 Tacoma which didn't have the security system. There's a W-B ground wire on the Limited harness that grounds the security system off the ECU, which I had grounded. I clipped the wire, and bang, engine fired right up! Runs like a champ with no codes. So although it took me days to figure it out, at least now I know what wire to use as my kill switch.

Smog ref appointment set for next week, so I should be able to get it up to Pismo for Surf N Turf.

Looking forward to 100 extra horses in the sand!

dntsdad

great. Glad you got it and kudos for updating this for future searchers.