Diesel problem Not Mercedes but Applies - PeachParts Mercedes-Benz Forum

#1 06-13-2002, 01:22 PM

Had a headache with an 89 VW turbo diesel.The engine was re-built - new rings, honed, new mains, new shells, crank redone, seals and the head was pressure tested at a machine shop- valves lapped and lifters looked fine and reinstalled. The engine starts right up with 1/2 a crank but has a steady small 1-2 foot long stream of blue - white smoke from the exhaust that turns into a billow of smoke when you rev the engine. At the same time there is an intermittent extremely loud metallic knocking sound that causes the engine to shake violently- pretty sure it was a sticking lifter or cam follower -but the wierd part is - the engine will idle smoothly while puffing the blue-white smoke then after a few minutes will start clanking (lifter sticking?) and shaking like it has a strong miss. Only problem is - if I loosen the injector lines one at a time and then tighten - they ALL cause a drop in engine speed - so all cylinders are firing even with the shaking like a miss. When it starts clanking with the miss - the revs go UP about 100-200 rpm and the smoke increases to a cloud. As the clanking goes away after 15-20 seconds the shaking stops, the revs go down and the smoke goes down to a puffing level again. Normally bad injectors cause black smoke and in real bad ring cases the engine oil is burned with the diesel and you don't normally see blue smoke out the exhaust. The smoke is the same color as unburned diesel on a cold start and continues even when the engine is at operating temp. I am leaning towards too much diesel being injected into the cylinders - so much so that the smoke is not black but blue - only thing is - the injectors were pressure tested OK before being reinstalled
Solution:
The knocking was a sticking lifter - ran engine until it started knocking and shut it down while knocking. Checked all lifters and replaced the offending lifter and cured that problem- sure sounded like a rod knocking though. Had a diesel man suggest that if an injection pump has not been used in a while (this engine sat for a year) they can cause a lot of blue smoke even if the car runs good. Sometimes they come back - sometimes they have to be rebuilt or changed. I filled the injection pump with ATF by putting the fuel inlet hose to the injector pump into the bottle of ATFand let it suck into the pump then I shut the engine off and let it sit for a day. Then I started driving the car for a couple of hours and slowly but surely the smoke started to disappear. It now is fine. Just learned another thing with diesels that I did not know. Hope this helps any one else who rebuilds an engine that has been sitting for a long time.

whunter · #2 07-02-2004, 09:54 PM

good information..

#3 07-05-2004, 09:10 AM

whunter - as an update - that engine is still working like a charm.
Morris