jbawden

Had my 93 for about a year now, prior to me it spent about 12 years of low use and very little....OK no maintenance. Father-in-laws truck, so I know the history all the way back to the original owner. Had 117k when I got it, 125k now. During my year, did a full cleaning and tune-up including turning up the pump. Makes good boost and runs strong.

No changes to the truck in the previous few weeks prior to my issue: yesterday I noticed at idle it has a slight white haze to it (this is after a 2 hour drive, so it was warm, same issue today after a shorter drive). At cold start up, haze really isn't present). I've made no timing changes to the pump, stock setting. Boost and power are as they have always been (good) and under load it's the usual cummins dark gray smoke. Starts super easy as normal and the oil level is fine and does not smell like diesel. The longer it idles, the the greater the haze. It's just a haze and its diesel stinky (vs. oil stinky). Once underway after extended idle, it's a little white, then is mostly normal, though a very slight haze is present at each red light. Based on my research, I'm going to guess the turning up the pump, installing a clean filter, a new lift pump, and previous use (lots of sitting and short trips) that maybe the injectors are tired and are leaking? If people agree, where is a good place to get new/rebuilt stock injectors? Don't want smoky after market injectors. I know this is common thread, but none of the OP's in all my search results followed-up on what solved the white haze issues.

Mark Nixon

With 125k, I have serious doubts the injectors are the problem.

Check your fuel pressure at idle and also double check ALL of your connections from the tank to the inlet of the lift pump.

I'm thinking air somewhere.

Mark.

jbawden

I did change the fuel filter a couple weeks ago but haven't driven it much until this weekend. Could air be trapped in the lines or are you suggesting a continuous leak? I bled the lines at banjo bolt (10mm bolt), but not at the individual injectors.

Mark Nixon

I'm saying check the supply side for leaks.
I know you mentioned you replaced it, but sometimes a bad lift pump can allow air into the system.

Another issue that has been known to happen, is that the coil in the fuel module, called a "draw straw", will have rust holes or fractures and draw air in that way.
Pretty unlikely, but still possible.

Given that the timing is correct and all else is kosher, air in the fuel cools the charge and causes it to burn ineffciently in a diesel, which is why it will white smoke and smell raw.
Injection timing can do this, as well.

You'd be surprised what just a pinhole in the right place will do to a fuel system.

Mark.

NE frmhnd

If you fill the tank til it's completely full, it should rule out anything in the tank. If I'm not crazy.

jbawden

OK, checked all the lines from lift pump back and it looks good. Also installed a known good lift pump, still light gray stinky haze. About a month ago, I adjusted the full power screw and then lowered the idle to around 750. After I installed a new fuel filter two weeks ago, seems like I'm getting better fuel pressure because the boost rockets up now when I stand on it. Would full power/idle mods have anything to do with haze at idle?

jimbo486

I wouldn't rule out the injectors just yet. Even though the motor has low miles, you should still try eliminating every possibility. Try cracking the lines at the injector open one at a time while the motor's idling. You should hear a slight change in engine noise as each cylinder "drops." If the engine noise doesn't change, you've found a bad injector. A bad injector that may be dribbling the fuel out between it's injection cycles can cause the white smoke or unburnt fuel.

jbawden

Would this troubleshooting technique work when the motor seems to idle perfectly? Motor really runs good and makes strong smooth power. I've read other posts that suggest 125k is a reasonable mileage to suspect injectors, so I don't know....

jimbo486

I don't see a problem testing the injectors at any time. Yes, 125k is a low amount but you still wanna be able to check injectors off your list if they're ok. It's one of the many things you can diagnose for free. Not to mention, it's easy to do. You wanna know exactly what the root cause is. Rather than spending time and money on other replacement parts just to find out they didn't fix the problem. I'm not doubting anyone's expertise or knowledge but testing the injectors hadn't been mentioned yet, to my recollection.

1992gen1_fan

I'd say get the injectors tested.
I got my stock injectors rebuilt and thats prety much cured stinky haze mine had, hazes a little while its cold but it is'nt as strong smelling, and after driving it there is no smoke at all at idle. Before, it was embarassing to let it idle in public lol.

Bencie

Make sure there's no air inlet or filter restriction, just to add to your check-off list.

jbawden

Tried a few more things; cracked each injector while running and all 6 made the same difference (meaning all cylinders are firing at idle) and turned the pump down, neither made any difference. In fact now it's hard to start unless I crack the throttle 1/4 way, then settles into a normal idle. I don't see any fluid leaks whatsoever. I really don't want to throw money at until I know the issue. Does the starting issue shed any more light on the problem? Kinda going back to the air leak idea, but have no idea where it would be. The fuel module was mentioned, is that the area above the filter (heater and so forth)?

1992gen1_fan

The module is in the tank.

93flatbed

I think Mark was on the right track, sounds like you have a supply side air leak somewhere. They can suck air and not leak diesel. So if I were you, I'd use a small amount of air pressure to pressurize the tank though the filler neck and have some one check for leaks. I've done this a few times on my fleet of junk and have always found the leak.

Mark Nixon

You're not crazy.
It would eliminate anything drawing air in the tank itself, almost right up to where the fuel fittings come out of the module.

Keep in mind, the '92 and '93 trucks all used plastic fuel lines, which means they are generally less likely to have rust issues, but can still fail near the ends.
Additionally, check that all of the fittings on the lines between the lift pump and head are tight, then do the same for the 2-piece line from the head to the injection pump.

Mark.