Rough idle after cold start, aka LF diesel experts!

[Mattew]

Hello fellow truck owners. So here we go again, fix one thing and another breaks, never ends. I search again for knowledge amongs you all!

Now I have bit of problem with idle in cold mornings. Glow indicator works, glow relays cycles, so it "should" do its glow thing. Cranking time is normal, pretty much same as with summer temps up 1s max, then it fires up with no hesitation. After that is pretty rough, had be on throttle and keep it at 1500rpm, lots of white smoke (unburnt diesel), almost like one cylinder is not firing. About 5-15 sec its all clears out, smooth idle at 1000, smoke pretty much clears out. It never happens once engine is all up to temperature or even when truck has been sitting for few hours (cold already by temp gauge).

I had suspicion on glow plugs, replaced them but no change. Measured voltage at glow plug rail -> 9,8V main glow, 6,6V afterglow (truck has been parked for 3 days so I guess cca 11,5V battery voltage). Even when main glow voltage is kind of low it all looks like glow/pre-heat is just fine.

I am kind of out of ideas atm. Bad piston rings? Cold advance timing? ONE clue I add to mix. I did had problem with main fusible link (FL 2.0L, goes from batery to fuse box) in past and never fixed it, it went away on its own. It could be culprit of anything or I am chasing a ghost??

 

[rdruss]

I think your concern about timing may be on track. Not sure how cold start timing may be controlled on your engine but white smoke at cold start is an indication that it could be malfunctioning.

 

[Mattew]

Timing can be advanced by spring loaded lever that is controlled by Automatic Cold Start Device (ACSD). That is all mechanical thing consisting plunger, spring and thermo wax that is heated by coolant. Coolant heats up -> wax melts -> spring push plunger -> timing lever moves -> timing is in normal position. That is theory.

I did just check it and with cold engine it seem plunger is in retracted (timing advanced) position. I will check it when I get back home and engine is all warmed up if plunger will be in normal timing positio n.

Btw this morning I did 3 full glow cycles (main + afterglow) but no noticeable effect.