Single injector flooding mystery.

[Devinmasters13]

Hey guys, I'm brand new to the forum and I have a quick question. I drive a 1989 240sx with a stock SOHC engine. I recently let a friend borrow it for the day and he overheated it and I had to replace it. I have the new engine installed, but my third cylinder keeps getting flooded. It's got the stock top feed injectors, with brand new o-rings. Brand new plugs, and it's timed properly. Brand new dizzy. I've checked everything I know how to. All my grounds seem to be in place. The harness isn't pinched, and I'm getting 12v to my injectors. I've even changed out the injector with three different injectors and had the same problem. A soaking wet spark plug, and exhaust that reeks of fuel. There is even fuel in my oil. I'm starting to think its the ECU, but I wanted to see what you guys think before I buy one. I'm kind of at a loss. Thanks so much guys.

[PapaSmurf2k3]

Welcome to NICO!
It sounds like you've done some good problem solving activities already. Have you pulled the fuel rail (independent of the manifold) and tried to prime by keying on, to see if it is a constant leak? That might tell you where it may be coming from.
You should also inspect any bores that it is going into to make sure there are no scratches or burrs that could potentially rip/tear/push an O-ring, and lead to a leak.

[Devinmasters13]

I have pulled the rail off but I haven't tried priming it like that though. I'll try that! I have replaced all the rings though. And they are top feed so any leaks would leak from the rail instead of into the cylinders. Would a constant leak potentially be from a bad ecu?

[PapaSmurf2k3]

Yes! The ecu (or wiring) could have a fault, causing constant voltage to the injector, causing it to leak constantly.