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Another Crank No start thread - r34 rb20 neo + t

Sxnjeet
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Sxnjeet Rookie

Sxnjeet

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Posted

Okay so, please read this.
car started and ran fine. got my tuned ecu by RSenthalpy, did a bunch of pulls to test it out and finally drive the car after half a year of it just sitting and idling at most. Everything was good, thing ran flawlessly and had so much power, didn't feel slower than a Prius anymore. Parked it back and turned it off. 
Next day, I install an AFR and start the car. Didn't wire anything to the ecu. Just gauge. 
Car started, but died out in about a minute. I figured it was cause my car was on a lift and the fuel was really low and old.

  • I add 5 gallons of fuel, still cranks but no start.
  • I remove all AFR wiring (tapped into double din acc and power wires but there was a nest of wiring there so I was worried I messed something up. tried to put it back to how it was prior to afr install.) Still cranks no start.
  • Changed spark plugs with brand new ones
  • Changed fuel pump with a new one (verified working)
  • Did compression test , compression came back all at 150ish.
  • All fuses are good, Relay seemed good but ill double check by switching similar relays around.
  • Verified MAF is working


- Ended up getting curious as to why fuel pump is not priming when ignition is on, so I cut the fuel pump ground and power and connected them directly to a portable jumper. I also disconnected fuel line to fuel rail to verify fuel is being sent.
So with direct jumper power, the fuel pump turns on and shot gas everywhere through the fuel pipe that I had disconnected, so ny doing that, I verified no clogs in fuel lines or filter.

- Tried starting the car with that jumper directly wired to power and ground, but car still did not start.

I'm guessing its a CAS issue but im a little scared to check it without messing up timing or anything else since I actually dont understand how to check CAS lol.

If anyone has any other suggestions or recommendations , please let me know.

joshuaho96 Veteran

joshuaho96

Posted
Posted

Get a timing light on it and verify it's sparking reliably at a sane ignition timing. Use a COP extension lead to be 100% sure about timing instead of hoping that the timing loop on the back of the engine is accurate. Make sure it's actually injecting fuel. MAF is not used on the stock ECUs for initial cranking.

joshuaho96 Veteran

joshuaho96

Posted
Posted
On 4/3/2025 at 8:56 AM, Sxnjeet said:

I'll be getting a timing light this weekend and also checking for spark. I was trying to avoid having to take all the Y piping things from the upper intake off again but I guess I have no choice lol

If you really don't want to touch anything you can try to trigger off the timing loop just to see if it's sparking semi-regularly. Don't trust it for actual timing measurements.

Duncan Grand Master

Duncan

Posted
Posted
On 03/04/2025 at 12:15 PM, MBS206 said:

My bet is there's a fuse somewhere you blew that feeds power to the ECU.

Or you've bumped something out behind the dash board.

Did you check Matt's suggestion? If the ECU is not powering up it will crank but not earth the fuel pump. You can also check the input to the fuel pump relay, it should earth for say 3 seconds when the key goes from ACC to ON, and also at all times when the key is at STRT

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