1990 Royal LP 25K forklift with Chysler 6 cylinder... smokes a bit after warmup...but

the spark plugs look perfect.... no carbon or oil whatsoever, light tan/grayish* electrodes. Smoke color...dunno, black I guess..but smells like oil to me. If it is burning oil, would perfect plugs indicate oil getting by something other than piston rings, like the valve guides


* https://www.championautoparts.com/c...3.img.jpg/Normal-Spark-Plug-1561122504789.jpg

Possible its valve guide, the exhaust valves usually don't directly contribute but positive pressure can get pushed thru the oil side of the system and thru the PCV ventilation.

Bottom line is if you don't care and are planning to own it for "awhile" it will probably go a long time. If you are thinking of future resale (which I suspect you may be) then none of the possible alternative sources are an easy fix within the engine.

We don't know with certainty how long the plugs have been in there, perfect plugs might be just a month of sporadic use......

More likely the valve stem seals are perished /cracked/worn and oil going down the stems .....if you are worried ,seals can be replaced without removing head .....ever seen the method of feeding electric flex into the cylinder thru a plughole ?...works real good ,and valve cant possibly drop.

john.k said:

seals can be replaced without removing head .....ever seen the method of feeding electric flex into the cylinder thru a plughole ?...works real good ,and valve cant possibly drop.

Click to expand...

Or compressed air....

if lift truck spark plugs are tagged platinum or iridium--good chance they are fake

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Leaking valve guides usually produce a puff of oil smoke on initial startup, not much if any after warmup.
Rings leaking will generally smoke all the time.
Simple cylinder leak down test will tell you exactly how well the rings and valves are sealing.

Ed

1990 forklift, so I am going to assume that it is equipped with a Chrysler industrial slant six over head valve engine and not the Industrial flat head. It could be running rich, however you should see that on the plugs. Smells like engine oil and assuming that your crank case it not over full,(I have seen a couple fork lift engines that had timing gear driven hydraulic pumps loose there front drive seals and slowly dump hydraulic oil into the crankcase)and yes with a diluted hydraulic/ motor oil they will smoke.
If its just lightly burning engine oil and there's nothing else wrong with the engine, you can change the oil and add to it a quart or so of Power punch, amounts used are listed on it. You can find it at Napa and a host of other auto parts stores.
I my take some heat for suggesting this but the stuff flat out works for light oil consuming control most of the time.

considering its 30 years old, there is a fair chance the engine is worn, run it for a while till you get the money together for a full rebuild. No point half doing it...thats if you want to keep it.
or Accept it as is for something that old.

Maybe something to do with a PCV system? The engine may have to hit a certain temp before the PCV actuates. PCV hose, box, or valve may have some oil in it, and it slowly gets dragged in once it actuates?