S1 RB25det S13 Swap; Won't start

[IDP FTW]

Hello all. I recently picked up an s13 with an S1 RB25det in it on CL for cheap. Bought it knowing it was an incomplete (missing IC piping and exhaust) swap and didn't run, with the intention of finalizing the missing pieces. It came with a Wiring Specialties harness.

As of today, I have finished the IC piping and exhaust and cannot get it to start consistently.

Symptoms:
-Will only start with the Coolant Temp Sensor unplugged. If the CTS is plugged in, it will not start at all. It will kick slightly but will never fire. If you start the car with the CTS unplugged, and then plug it back in while running, it will die almost immediately. When running, it feels like its misfiring and is very rich.

Here is a list of the things I have tried...

-Verified wiring from ECU to CTS is correct

-Visually inspected harness for crossed/frayed wires. Looks ok.

-Checked and added a few more grounds to the head and block. Ignition harness ground wire on the coil pack bracket is intact and tight.

-New battery, and hooked to a battery charger while testing.

-New plugs (BRK-7e) gapped to .028

-Inspected ECU motherboard. Doesn't appear to have any corrosion or broken links. Tried a different ECU that was in supposedly in good running condition. Will not run with the CTS plugged in or unplugged. Visual inspection of the motherboard looks to be fine.

-Tested CAS by removing and spinning by hand. Can hear injectors click but only get consistent spark on cylinder 1 & 6 when grounding out the plugs. I tried moving the coil packs around, issues does not follow the coilpack. Cylinders 2-5 have inconsistent spark. Replaced CAS with a refurbished one and have net the same results, though spark appears to be stronger on cylinder 1 and 6. 120 and 1 degree signal wires are correct according to an R33 ECU pinout.

-Tested Ignitor for resistance and found there to be no resistance on several pins. Replaced Ignitor, no change.

-Pulled fuel rail and had injectors flow tested and cleaned. Lower o-rings were torn on most of them. Repaired and replaced, no change.

-Tested all connections to MAF, ignitor, CAS, CTS, Ignition harness for continuity and power. Everything looks right.

What am i missing?

[TheRealSy90]

Sounds like it could be an engine harness issue. I've had bought harnesses from WS two times that had to be fixed out of the box due to wires being at the wrong ecu pins. Not sure how that passes their "bench test".

[IDP FTW]

Originally Posted by TheRealSy90

Sounds like it could be an engine harness issue. I've had bought harnesses from WS two times that had to be fixed out of the box due to wires being at the wrong ecu pins. Not sure how that passes their "bench test".

That was my thought as well. I've tried to trace down most of the important wires, and they all LOOK like they are going to the right place. But I suppose something could still be off.

[Jfornachon]

Do you have an extra cts? If so connect the spare cts and start it. If it runs then you know you have a bad sensor in the engine. If the spare sensor does the same thing then you need to look at either the wiring or the ecu. Those are your two options with the info you gave us.

You can never have too many grounds, but you can have too few.

Have a great day,
jared

[IDP FTW]

Thanks for replying. I have the original CTS that was in the motor when I got it, but nothing changed. Tried another wiring harness and still have the same issue.

The second ecu will not start the car at all, regardless if the CTS is plugged in or not. So maybe there is something there?

[Jfornachon]

Have you contacted WS? What about an aftermarket ecu?

Have a great day,
jared

[IDP FTW]

WS wasnt much help. They are both stock ECUs that I have. Trying to find someone local to test their ecu or vice versa, but no such luck yet.

[feito]

you didnt mention your fuel pressure, how is it?
Get a fuel injector noid light tester, they're very handy. Test your injector pulsations one by one.
I take it you're using the right ecu, right? Having an igniter, you're 100% sure you're using and tested a series 1 ecu?
Do you have the right CTS?
Check your harness ecu plug. I couldnt get one or two cylinders to fire on one of my rb25's once and it turned out to be a dirty pin at the ecu plug. Can't remember if it was for an injector or a coil. I dont know how old your harness is or how it was store, but humidity can really affect electronics.

[IDP FTW]

I will check fuel pressure. I pulled the CAS and spun it by hand while holding a screwdriver to the injectors, all clicked. Wouldn't this be a similar test to a noid light?

I assume I am using a series 1 ECU, the part number is 23710-21U01 which appears to be for a Manual S1. The other ECU number is 23710-21U60(the ecu that wont start no matter what)

The CTS I used to replace is part number 22630-44B20 from Nissan.

Harness plugs look clean.

What does unplugging the CTS do exactly? From what I understand, it puts the ECU into a rich state, assuming the engine is cold, right?

[Jfornachon]

The cts tells the computer what the temp of the engine is. When one fails it goes to a cold reading which is cold making it run rich.

I really think it comes down to the computer. If I were you I would make a spread sheet and check every wire to a wiring diagram. Make sure the wire you test goes to the proper ecu pin and component location. Maybe WS can send you one for reference. After you test it check it off. Make sure that it doesn't have a short in the CTS circuit. A simple continuity test will confirm that. You will have to do all the testing at the ecu connector. Once you check and confirm the whole harness You can either condem the ecu or check each component which is what I would do.Its all time consuming but I can't tell you how many times I got fucked when I took someones word when they said that "they checked it".

Have a great day,
jared