Thick white smoke at startup

[jd110]

The problem could have shown up now because of the different cetane rating of the fuel. The winter blend has a higher cetane level.

 

[Sadler]

Same problem with my 4120, now with close to 100 hours: heavy white smoke on cold start. Happens about one out of three starts. Doesn't seem to matter whether it's cold or warm weather. I can stop the smoking by turning tractor off, then back on, as though something is being reset.

Dealer has the tractor now, fixing that and my erratic fuel gauge. (Thanks to TBN and Joecdeere, I was able to give them the exact part number for the fuel gauge fix.) I'll report back on whether their fix works for the smoke and the gauge.

 

[tillboy2001]

Since the dealer won't have the part they want to 'try' until next week (early), I was thinking of doing a little troubleshooting on my own to at least prove the problem is related to this sensor or not. So I'm thinking about getting the tractor up to operating temp and then unplugging the sensor for no more than maybe 30 seconds to see what happens. I guess my only issue is I don't know what an unplugged coolant temp sensor will do to the computer as far as what the computer will tell the engine to do at that point. Anyone know? If it will cause the computer to think it's cold and then cause all this white smoke, that would be perfect because I could prove that's the problem. If it won't reproduce my problem of the thick white smoke at startup, I guess there's no point in trying this little test. Any of you diesel gurus out there know what would happen?

The mechanic talked to John Deere and they suggested the sensor he should replace first...so that's what he's waiting on.

 

[Sadler]

Got my 4120 back from dealer Friday. I've started tractor cold maybe four or five times since then and have not had the heavy continuous smoke on start up I was getting. Could be just luck, but I think not. Mechanic said the problem was with the governor; not sure if he just adjuted it or repaired it. I told him about the idea here of the coolant temp sensor possibly being the culprit but he said it was not likely that since the coolant is cold when it does it. He also recommended I start engine at idle rpm setting rather than recommended 1/3 throttle setting. With these two changes, I'm no longer getting the persistent smoking on cold starting, at least so far.

Also had fuel gauge sender unit replaced and this appears to have fixed the erratic fuel gauge reading when tank is less than half full.

 

[tillboy2001]

I'll mention this to my mechanic. Thanks

More info from a test I did this weekend. Sat and Sun when I started it, it had the heavy white smoke and ran a little rough. So I immediately shut it off, waited a few seconds, turned on key and waited for glow light to go off and then started. After starting a second time it ran normal and no white smoke.

Hmmm...well now I don't know what to think because I just got off the phone and teh mechanic said he talked to a JD engineer and he said the engineer he spoke to told him he's seen this problem before and suggested the new sensor. So I'll let him do his thing and see what happens. Worse case is it's not fixed and he'll just have to come back out to fix it later. They do all the repairs on the customer premise unless it's something they need to do in the shop. This guy is VERY easy to deal with. He keeps saying "Hey it's a new tractor and if you've got a problem we're going to fix it" every time I ask about some little goofy thing like the oil dipstick leaking a litle.

 

[KennedyDiesel]

Depending how the sensor operates, unplugging it should tell it you are coleder than you are which should maximize cold starting efforts. I would think that Deere/Powertech would have a chart showing what the resistance of the sensor should be at set temps so it could be simply tested rather than just replacing it.

Sounds like adding the heat of a second glow cycle helped. I'm not familiar with whether this engine uses glow plugs or intake air heater. If you have a block heater, it would be interesting to see how this helps also.

 

[tillboy2001]

JD's reading material says this engine has quick acting glow plugs.

Hmmm...wonder how I can boost her up to 66 horsies? /forums/images/graemlins/wink.gif
http://www.deere.com/en_US/rg/productsequipment/productcatalog/ind/t2_pt/4024/series/index.html