[SOLVED!!!] What's the strangest reason your truck wouldn't start? (Yes, I need help)

Thanks for the suggestion. The relay is good; the fuel pump turns on and gets fuel to the rail (verified by smell and by cracking the banjo bolt). The problem (in my opinion) is the signal that temporarily grounds the fuel injector, allowing it to spray fuel into the cylinder and the subsequent signal to the ECU telling it there is fuel in the cylinder, and the follow-on signal to the distributor to fire the coils and send spark to the plugs. For some unknown reason, I get no injector impulse and therefor no spark at the plugs. I’m leaning towards crank position sensor, because from my understanding this is where that initial signal comes from. The resistance on the OEM plug and the replacement (Bosch/Duralast) part both check out according to the FSM. However, as people have stated before, Denso to be sure...so maybe I’ll order another OEM crank sensor.

 

As I stated earlier in your diagnosis - is the distributor shaft turning when you crank the engine? Seeing the rotor turn while cranking the engine should show you this. If it doesn't spin, you will not trigger the computer for the pulse needed to fire the engine up. Just a thought.

 

You've got this backwards. The ECU receives the crank/cam position signal and determines when to spark each cylinder. The ECU sends the signal to the igniter which sends the signal to the coil. When the coil fires it sends an electrical pulse back to the igniter, and finally the igniter sends a signal back to the ECU to verify the coil fired. If the ECU doesn't receive this for a few consecutive spark cycles, the ECU will stop grounding the fuel injectors, thus cutting the fuel to the cylinders.

The tachometer uses the IG- signal to determine RPM. In older cars this was the ignition coil negative. On these trucks the IG- is generated by the igniter based on when the coil is fired. If your tachometer isn't showing any RPMs when cranking then it's not getting that IG-. Someone else might verify that the tachometer actually moves while cranking because I'm not sure that the RPMs are high enough to register on the tach.

Seems like you need to verify the proper voltages at various spots. In particular the distributor.

A repair manual might explain how to test for the spark signal coming out of the ECU. You want to divide and conquer to find out what is causing it to not spark.

 

[SOLVED!!!]
Thanks to everyone here who helped me sort through all of the potential causes of my no fuel/no spark issue with my 1985 4x4/1995 Tacoma 3RZ swap. As some of you suggested, the crank position sensor was the culprit. It wasn't the distributor, the ORS wiring harness, grounds, igniter, etc. I had already replaced the CPS once, and really didn't think that was the issue but it was. Today I replaced it [AGAIN] despite never thinking that could have been it since I already replaced it once and the original bench-tested within specs according to the FSM. So, two crank position sensors, within Toyota factory service manual specifications were actually bad. That tells me that the resistance test on the CPS is completely unreliable. I won't ever forget that in the future!

I've got some things to sort through still, such as a high idle (~1100 RPM), difficulty shifting into 1st or Reverse (probably synchros), and some rough steering (maybe need to bleed the power steering or just add more fluid). Then I can FINALLY get to making her roadworthy again. On the list right now is an exhaust system, cab stripping and lining/soundproofing/carpeting, wheels and tires, upgraded lift (hi-steer probably), and finally either paint or Line-X on the exterior. I've been waiting on these to see if I could get her running first. It's been a long road that started last October. Thanks to you all for your troubleshooting suggestions and help. I tried every one of them, and some of them more than once. But in the end, it was just a faulty crank position sensor that I first changed out months ago.

Since starting this project to get my Dad's 1985 4x4 upgraded and back on the road, he has lost most of his memory, recognition skills, and cognition to dementia. He won't ever remember this truck or selling it to me just a few years ago, but I will always know that it used to be his, and I'm keeping it alive so that the memory of him driving it won't ever die.

Thanks again.

Gabe

 

I knew it!!!

Congrats on getting it running.

 

105 Pages......I read most of them, and really got scared right along with you. Was the Crank Position Sensor new.

 

Congrats on getting it running! I’ve been following this thread hoping for this outcome. Way to stick with it!
Sorry to hear about your dad, I’m going through something similar and it’s hard to say the least.

 

Yes, it was. But it was not OEM.

 

For anyone interested, my rundown on the 3RZ swap is posted on Pirate 4x4. Here is the link. Also, I just finished cleaning out my throttle body and IAC valve. She's idling around 750-800rpm instead of the 1200-1400 when I got it started. What a difference! Hopefully, this will help my gas mileage too. Thanks again to all who stuck with me through the troubleshooting.

 

Having same problem as you. But I change the crankshaft sensor already and still got a no start.

 

Does the horn work?