The be all end all “My STX 12f or 15f or Ultra LX is not running right” Thread

[J_0sh]

Joined this forum just because of Seans awesome write up, but im still having some issues with my 12f, its technically not a ski but a 12f in a flatbottom boat, it ran great then i put it in my shop to do some work to it and i now only have power/ fuel to cylinders 2 and 3, its driving me insane but im at my wits end. My display is currently Fooked so no help there. It literally ran fine before i put it in my shop. Any help or insight from the master would be greatly appreciated.

[macGruber]

The fuel injectors are super easy to pull on that ski. Pull them off and test them. Look in the back side of them to see if they picked up any trash from the fuel pump. The fuel pumps inside the tanks on these things corrode badly especially when they are left without fuel in the tank. This causes rubbish to be picked up and sent to the backside of the injectors a lot of the time. Get out your magnifying glass or macro photo on your camera and take a look in that backside to see if there's any junk in there. Also recommend having them cleaned anyway if you haven't done that.

[J_0sh]

Ive already done that, i can swap the working injectors cylinders 2 and 3 with 1 and 4 and they dont work so i know its not the injectors, i dont have spark on both of them cylinders either. Could it be a bad Tip sensor? All of my connection are solid, none show any sign of corrosion and my harness is free of any loom and black tape, the wiring is in great shape. Idk what else would kill my spark and fuel partially.

[smokeysevin]

Ive already done that, i can swap the working injectors cylinders 2 and 3 with 1 and 4 and they dont work so i know its not the injectors, i dont have spark on both of them cylinders either. Could it be a bad Tip sensor? All of my connection are solid, none show any sign of corrosion and my harness is free of any loom and black tape, the wiring is in great shape. Idk what else would kill my spark and fuel partially.

Have you actually pulled any of the block connectors or joint connectors apart on the harness?

There have been 2 or 3 cases in the last year or so of corrosion in the harness that kills spark or fuel to one pair of cylinders.

I think the last case I remember was corrosion at the ecu connector.

Sean

[J_0sh]

Have you actually pulled any of the block connectors or joint connectors apart on the harness?

There have been 2 or 3 cases in the last year or so of corrosion in the harness that kills spark or fuel to one pair of cylinders.

I think the last case I remember was corrosion at the ecu connector.

Sean

I have unplugged every single connector on this wiring harness and nothing looks corroded. Im about to check continuity between all thr wires at the connectors. Could my tip sensor be causing this? Its the only one that looks corroded inside the little black box.

[smokeysevin]

I have unplugged every single connector on this wiring harness and nothing looks corroded. Im about to check continuity between all thr wires at the connectors. Could my tip sensor be causing this? Its the only one that looks corroded inside the little black box.

Tip sensor "should" kill all of them not just half but I have not tested that specifically. I have a few spares if you need a fresh one to try.

Sean

[J_0sh]

Tip sensor "should" kill all of them not just half but I have not tested that specifically. I have a few spares if you need a fresh one to try.

Sean

I appreciate it man but I ordered a used one from fleabay it should be here tuesday, it was only like $18 shipped so not to bad. But since my last post i have ohmed my crank, cam and temp sensors all of which check out to be within spec. Ive removed the little white cylindrical connector that goes next to the power cable and added more grounds to the motor but still no start. Im thinking if this tip sensor doesnt fix it ordering another wiring harness. Maybe somewhere somehow something got fried while i was welding on it and i just cant see it. I didnt have a battery in the boat at the time of welding but so idk.

[steve45]

Maybe somewhere somehow something got fried while i was welding on it and i just cant see it. I didn't have a battery in the boat at the time of welding but so idk.

If you had any ground wires hooked up, you may have fried the ECM. Not sure how, but welding does weird things to electronics. If you were TIG welding with a high frequency start, that would probably be worse.

[J_0sh]

If you had any ground wires hooked up, you may have fried the ECM. Not sure how, but welding does weird things to electronics. If you were TIG welding with a high frequency start, that would probably be worse.

So i just got my parts 15 mins ago, installed the tip sensor and nothing. Same things happening. Im about to get on flea bay and order a new harness and ecm. Im out of ideas.

And as far as the welding goes i was using a spool gun and none of the grounds or any electronics were connected to the engine whenever i was welding, im completely lost.