Swap was running fine and now white vapor/smoke from one tailipe

[Jason Banks]

https://youtu.be/N1jBkT4DQAA

I have not had my swap running very long and it hasn't even been driven on the road. Started it up today and I have this happening.

Engine is a 6.0 with 862 heads that I bought remanufactured(heads only, I pulled engine from a running driving truck). Stock shortblock that I re-gasketed and installed the different heads and factory intake etc. Aftermarket wiring harness, using adapters to connect to the injectors, because the intake, fuelrail, throttle body and fuel injectors are from a 2003 suburban, that was running and driving.

My first thought at seeing this was, that's water, I have not run the engine very long and there had been a fair bit of condensation coming out everytime I start it. Last time before this was the longest I have run the engine.

I pulled the plugs on the passenger side and 3 of them looked blackish but dry. The 4th one had a dry tip, but I think the electrode had gas on it.

Stuck injector? Wiring problem? Still looks like water to anyone?

Before installing the injectors, I used a tool to pulse the injectors and run Berryman through all of them and they all seemed to work well. I also ran them through the ultrasonic cleaner. Maybe I messed one(some) up?

[LS short box]

If you think its coolant go to Oreilly's and borrow their radiator tester. Put it on the radiator and see if it maintains pressure.

[Jason Banks]

I have one of those testers, I'm really thinking it's an injector with everything smelling like fuel, just looking for someone to look at the video and offer an opinion.

The exhaust tips in the video are not welded on yet, and I pulled the passenger side off and it smells like fuel...

[WorldsCrappiestTruck]

A bit of a pain, but swap injectors from the passengers side to the drivers side. That would help narrow down fuel vs engine gasket issue.

[AussieinNC]

What trans is in this truck?

[Jason Banks]

4l80e

[Accelo]

It almost has to be water. Is the coolant level dropping? You can also have the coolant checked for exhaust gases or can purchase the kit and do it your self.
A leak down tester may help.

A stuck injector would likely hydraulic lock the motor. Many of the scan tools will let you disable injectors one at a time. Then you watch for an rpm drop.

A compression test may help. I have two style compression testers. One has a schrader valve that only allow air in. The gauge stays at peak cylinder pressure till you release schrader . The other dumps everything from the hose , gauge and cylinder. So when you quit cranking the pressure starts falling immediately and continues till the pressure in the cylinder is zero or you push the schrader and dump the pressure. Using the second type gauge you can watch as the cylinder pressure drops you can kind of calculate the condition of the valves and rings (and any leaks in the head gasket).
I just did a compression test on an LS1. Cylinder pressures went to a nominal 200psi. Then, when I quick cranking, I timed the seconds it took to drop from 200psi to 100psi. A good cylinder would take 60 seconds to drop the 100psi.
This way I got a compression test and a cylinder pressure drop test all in one.
Do this twice for each cylinder. If the pressure goes up on the second try remove the gauge and crank the motor. I have shot water half way across the shop using this method.
Best of luck

[Jason Banks]

Finally got a chance to check this out this morning.

Cylinder 4 spark plug smelled like fuel and looked like it had raw fuel on the insulator.

The injectors have a switched power wire(pink) and a ground trigger wire. Put my multimeter on the wires for cylinder 2 and the trigger showed no continuity to ground, but on cylinder 4 it did.

Like I said I haven't driven this truck on the road and it has never really gotten up above about 180 in temperature.

I had caught a glimpse out of the corner of my eye that it looked like the main harness going to the computer looked different. Sure enough a zip tie had come loose and the main harness was touching the exhaust. The only real damage was to the outer cover and the single trigger wire to cylinder 4 fuel injector.

Like many of you I saw the white smoke and immediately went to 'oh crap' that's water/coolant. But it looked strange to me because it was dissipating quickly. Initially pulled the radiator cap and the level looked fine. Then with the fuel smell I was thinking it was a stuck injector, even though I had cleaned and tested them all thoroughly before installing them. I even ordered an injector. You can also hear in the video that it sounds like it is misfiring. I wanted to check the computer for codes, but I have been disconnecting the battery every time I shut it off. Didn't even occur to me initially that it could be triggered all the time and not stuck.

It's a relief that I don't have to pull the fuel rail off and get smelling like gas. That is the main reason I couldn't do it last week. Had some personal plans that didn't include smelling like gas.

Lesson learned. White smoke is not always coolant.

[Accelo]

Wow, that was lucky. The computer grounds the injector to fire it. The grounded wire had the injector firing continuously. Or intermediately if that's how the ground was.
Good find. The nose solved this one. Good Job.