7.3 Smoke on cold start

[gtbensley]

I have a 95 E350 7.3 that has been smoking some on colder start....by that I mean anytime the engine has not been run in 24hrs or so. It does go away when its hot out (70+) but smokes a decent amount of bluish smoke. Its burns the eyes pretty bad and smells a bit like fuel so I am apt to say its fuel, not oil being burned.

Its been doing this about a year or more. This past month I pulled the injectors and replaced all the o-rings, glow plugs, UCVH and VC gaskets, and ICP sensor, the old o-rings were intact but it was clear some oil was pooling on the bottom of the injectors as they had some residue built up.

I am still getting blue smoke in the same starting situations. Once it has run a couple minutes the smoke is completely gone and never returns until it sits again. Engine starts and runs great in any temperature. Passes contribution tests and buzz tests.

Thoughts on what could be causing this?
Bad injector?
IDM on its way out and causing timing issues?
Normal?
Turbo seals starting to let go....but zero smoke at temperature or load

I messed up an o-ring or didnt torque an injector correctly? Possible but I doubt it, wouldnt this be apparent all the time while running? I have about 400-500 miles on it since that repair. Smoke seems the exact same as before.

This thread is spot on, except I am 100% stock except for no cat and a walker BTM muffler.

http://powerstrokearmy.com/forums/showthread.php?t=31194&showall=1

 

[Buliwyf]

Could be wet stacked. Wet stacked exhaust systems have a very sweet, but spicy smell on startup. It'll even burn your eyes a little, and have a blue smoke that isn't quite like burning oil. I can spot it in 10 seconds every time because of my generator work, and the fact that I kinda like that smell. (which is odd)

It's just a bunch of tar build up in the exhaust because a diesel engine runs inefficiently under light loads. Like a carb'd car running rich.

Pull a heavy trailer up a hill at 80mph. That'll burn all that stuff out. Basically, we need higher EGT's.

You can also check for blow-by with the oil cap trick.

 

[gtbensley]

The smoke is not sweet at all, very pungent.

I doubt its wet stacking....rig is pretty heavy and gets run with a decent load anytime its going down the road, but I do drive it gentle. Also has a high idle that I use if parked and letting idle....which is very rare.

Have checked the blow-by with the oil cap. When cold I get a light mist from the filler tube but no noticeable pressure. Once warm the mist is gone and absolutely no pressure....I can leave a piece of paper on it and it wont move.

 

[Buliwyf]

I'd let it slide then. If it goes away, I'm ok with it. A turbo seal, generally is pretty obvious a mess. Not something that comes and goes.

It's normal to smoke a bit when cold. It could just be one cold cylinder, or an injector dumping a little too much fuel until it heats up and loosens up. If there's no solid carbon in the exhaust and no goo anywhere then that's good. If the intake heater is gone, INOP, or was never even there, that's a good clue.

And if it gets better for a few days after running the truck really hard, that's ok as well. If it gets worse after easy days, that's a good clue.

If it's a little smoke, like the vid on that forum, I'd ignore it. Not the first time Ford's had some weird fuel timing setups. My engines will smoke out an entire city when they really fail.

Big mitsubishi diesels can fail to fire a few cold cylinders (like 8 or 9 while the other 11 cylinders get the engine rolling along just fine) on startup fill the exhaust with raw fuel and then start shooting fire balls out the exhaust. Then they warm up and run fine. Pretty cool, except when it's a court houses generator. Generally white smoke with a little blue before that fire ball. Or if they run out of fuel, or get some air in the system from a filter change, I think the injectors or pumps hang open and dump excess fuel into a few cylinders. Trying to explain that's normal to a customer, is nearly impossible.

I've seen perfectly good diesel engines make each of the different kinds of smoke. John Deere H135's all have leaky heads and coolant use (according to the normal shadetree mechanics). Except they ain't using any coolant , just messing with us. That engine makes weird smoke pretty much normally across the board every time.

 

[gtbensley]

I dont believe it has an IAH, think thats on later model years. Yeah it might be normalish I suppose. Its a pretty big cloud at first but does clear up. I wouldn't say its just a little but its also not pumping out volcanic amounts either.

I will have to see after running it harder if that changes anything. The exhaust does have carbon on it, but what older diesel doesn't?

 

[Buliwyf]

Normal carbon coating like a gas engine is fine, but not gooey chunks of carbon. Or flaky chunks of carbon.

 

[gtbensley]

Not that I can see. Haven't pulled the DP and looked but the tailpipe is normal carbon black.

 

[rayra]

Worn / cooked engine valve stem seals. And guides.

https://www.youtube.com/watch?v=CnxyvMAwFrg

had similar trouble with the SBC in my '85 C-10 after about 100k mi. Have it again now. Oil seepage, burns off quickly on startup but manifests as enough pollutants to fail a smog check in CA.

 

[gtbensley]

Not all that common on a 7.3 to have the valve stem seals go bad, but could be.

Any idea how I can narrow down on these ideas? Sure wont know sitting behind my keyboard but I also dont want to rip into the thing. Runs great and nothing really wrong, just doesnt seem normal to me.

 

[gtbensley]

Just thinking, I never replaced my fuel filter after the O-rings. I wonder if its got oil in it still and causing this when cold? Probably not.....

 

[toastyjosh]

try this
get a new fuel filter for the fuel bowl, drain the fuel bowl. Pour in some diesel clean (silver) or seafoam or other additve. Install new filter. Take the rest of the additive and dump in the tank like ten oz or so. Start truck.

Run it for a while, drive around, get it up to hwy speeds.
Let it sit overnight see if it helps.
If it does nothing then we can go from there.

 

[VOODOO7.3]

If it starts fairly easy after being plugged in, you probably just need a new Glow Plug Relay. I used this:
http://www.google.com/aclk?sa=l&ai=...&q=&ei=BjcnVY2yIMX6sAX-x4LoAg&ved=0CEMQpyswAA

Both the Western and the Stancorp Monster relays have 100% duty cycles which is way better than stock. I used the Western because it is inexpensive and about same size as stock. Very easy swap. Blue smoke gone!

 

[back woods]

Try a different CPS, a lot of cold start blue comes from the CPS. Every 7.3 I have owned puff some blue when cold. A bad CPS will make for a TON of blue smoke. Nothing bad about it, pretty normal for a 7.3.

 

[gtbensley]

The glow plug relay is about a year old, stock ford one. It starts fine even down around 10-15 degrees so I imagine it is working. I guess I could swap it for a larger one and see what difference that makes. I replaced the CPS a few years ago with the updated one, but again, I could swap it for a different one and see if that changes things. Its not a TON of blue smoke, but enough to be considered not normal to me. My neighbor has a 97 7.3 with the cat in place and his puff just a little when starting and clears up fast.

Just ordered a new fuel filter and air filters as I need both. Will try the seafoam in the housing when I change it.

Ill plug it in and see if that changes the amount of smoke. Its about 45 degrees and raining currently, cold the motor will crank for .5-1 second and fire up and idle smooth after about 1-2 seconds of loping idle.

 

[back woods]

Here is a video of my 95 7.3. I was convinced it was getting tired and needed new o-rings, had blow by, etc. Ended up being 100% CPS related, I have found that the different colors of CPS can make the truck different. Some go bad and the truck wont run while others can act up for years and make you think it is something internal.

https://www.youtube.com/watch?v=qhOHbstzLnc