scpoehl

Hello all,

My first post on this forum, but I am having a pretty unique issue with my 1uz rebuild and was curious if anyone here had any thoughts, I had my (kind of) first start yesterday of my 1994 1uz I am building for a swap. Today I did my first test start, Everything wired up and was cranking correctly with the proper amount of voltage and fuel flowing from the external tank with a Walbro and back into the tank with fuel pressure regulator screw popping up like it should and I can audible hear air escaping with no leaks anywhere though. I currently have what was outlined in this post as the bare minimum should be for needing this engine to run. https://www.clublexus.com/forums/per...-on-stand.html The ecu is also a freshly professionally rebuilt unit from a reputable Lexus ecu shop so I believe that is out of the picture. The passenger sides plug wires all seem to fire just fine, tested with a screwdriver and can visibly see them arcing so I don't think its likely a no spark condition is present

The engine cranks great and sounds perfect but will run for a second or two, and then fuel will dump out of the passenger side exhaust manifold and it will die. I would say roughly an 1/8th to 1/4 of a cup (and trust me, its not condensation.. I saw flames xD) . For whatever reason that bank continues to spit out fuel, the driver side bank is completely fine and dry with normal exhaust gases. Any help would be fantastic, I am just a little bit lost and have not seen anything like this before. Currently I am using the machined, billet early style rails, used (condition unknown, I have only cleaned them) stock injectors.

The only possibilities I can currently think of are either A.) fuel injector stuck open or otherwise failing wide open causing the cylinder to fill with gas or B.) Something on the rail (Fuel Pressure Dampener and fuel pressure regulator related?) Either way, I do have a set of the rounded style rails and have found some good injectors locally so that will likely be my next stop but I would appreciate any ideas!!

Thanks a ton,
Sam

MatClever3

Did you ever find a solution to this problem? Im having the same issue. Fuel dumping in my #6 cylinder.

scpoehl

Hey Mat, I did indeed, it was a stuck open injector on that cylinder that when pulsed instead of priming the cylinder with a small amount fuel for the stroke it will throw fuel at a 100% open rate.

This is the order I would go down personally if I was you and what helped point out the issue to me.
- Check firing order: It sounds basic but make sure your spark plug wires are going to the right cylinders, having this wrong will cause spark at the wrong time and prevent combustion

- Check for spark: pull either the plugs or the wire from each cylinder on the bank giving you problems and make sure there is spark, injectors don't know if there is spark or not and will continue to dump fuel in the cylinder regardless of ignition condition

- Swap an injector: This is ALMOST always the issue, When this issue happened to me I did countless hours of forums searching and over 80% of the cases of this either a bad used injector or a cheap off brand replacement injector was at fault and displayed a stuck open condition meaning 100% fuel when pulsed. This annoyingly is almost impossible to diagnose out of the vehicle as you have to pressurize the rail and fire the injectors at the rate the ecu does, not just a random pulse test.

- Check fuel pressure regulators: Did you recently re install your rails? are all washers in the correct spot? is the o ring correct? is there good fuel return flow if present on your rail system? these seem like no brainers but can cause rail over pressurization and excess fuel dumping

-Check timing - This again can seem basic and no brainer but will cause you a myriad of issues, one of which a no start/spark condition sometimes only on one side causing fuel/spark at the wrong time


I would take your time and go through each of these, I am willing to bet one of them will solve your issue. Out of all of them mine as many others ending up having a dead stuck open injector

Yamae

Have you checked the waveform for your #6 cylinder injector driver? I worry that the drive transistor is always ON or the Zener diode is damaged as is posted here.
https://www.clublexus.com/forums/ls-...tify-this.html