diesel runs rough on start-up

[jbarker855]

I have a 2004 John Deere 4120 with a 4 cylinder turbo diesel. The problem is that when I start it after it has been sitting for a few days, it runs very rough for about 5 seconds, and then clears up and runs good. In that first 5 seconds or so, it sounds like it is starving for fuel, and sounds like it wants to stall. It acts like my other diesel sounds when I have almost run it out of fuel and there is a little air in the lines that needs to be bled out. If I restart it later that same day, it runs fine. There is no stumble or rough running.
This tractor starts every time, and does not stall out, but I suspect this initial rough running is not normal and I want to fix it before the problem gets worse.
Any suggestions? Thanks in advance!
-Jay

 

[Soundguy]

do you see any dark dust collecting around any of the injectors or injector lines?

soundguy

 

[RoyJackson]

Did you use the glow plugs prior to starting? It's probably getting a bit cool in New York state...

 

[jbarker855]

Roy-
It is getting cold, but my 855 starts up good even without the glowplugs. And the indicator on the 4120 is not even lighting up to suggest that it wants me to pause to let the glow plugs warm up. Also, this problem was present even a few months ago when it was warm.
Soundguy-
I will check the injectors. Sounds like you suspect a small leak which is bleeding off presure/letting in air?

 

[RoyJackson]

Roy-
It is getting cold, but my 855 starts up good even without the glowplugs. And the indicator on the 4120 is not even lighting up to suggest that it wants me to pause to let the glow plugs warm up.
Soundguy-
I will check the injectors. Sounds like you suspect a small leak which is bleeding off presure/letting in air?

Those Yanmar engines (like in your 855) do start quite well in cold weather...not so the Deere engines in your 4120.
Even if the indicator light doesn't light up, try the glow plugs anyway...easiest thing to do initially and costs nothing but about 20-30 seconds of your time. I suggest you do this before going into the injectors.

 

[jenkinsph]

Those Yanmar engines (like in your 855) do start quite well in cold weather...not so the Deere engines in your 4120.
Even if the indicator light doesn't light up, try the glow plugs anyway...easiest thing to do initially and costs nothing but about 20-30 seconds of your time. I suggest you do this before going into the injectors.

I agree with Roy on this, an easy first thing to try. The Deere engines doesn't start up as easily as the Yanmars.

 

[deere5105]

My 5303 does same when starting. Seems worse in colder weather. I do not have glow plugs, but do have Intake Heater. After trying that out makes a huge difference. My previous 5105 had same motor but was not turbo and did not have this cold start issue.

 

[Soundguy]

yes.. I'm suspecting a small leak / air.

easy enough to test and do the glo as well.

soundguy

 

[dusty3030]

My 2011 4120 does the same.
Not bad unless it has set up for a couple of weeks.

 

[jbarker855]

Well maybe it's just normal for these tractors?
I will still try the glow plugs to see if it helps, but I need to wait a few days. The tractor only runs rough on startup if it has been sitting for several days. Since I used it yesterday, it will start fine today no matter what. I'll let you guys know what I find.
If using the glow plugs does not make a noticeable difference, the next thing I will do is let it sit for a few days again and try priming the fuel system using the plunger on top of the fuel filter housing.
-Jay