Truck Repair: STC, cold start miss, cant remeber, directional arrow
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Question -
I have a 1990 Cummins STC365 CPL1211, 300,000 miles that either #1 or #2 or both cylinders have a dead miss with white smoke on startup. It will eventually and completely disappear if I blip the throttle a time or two or sometimes just restart it. It is worse when cold. I have adjusted the valves and injectors and switched #1 and #2 injectors with #3 and #4. The miss stays on #1 and/or#2 cylinder. This makes me think it is not the injectors. When the miss disappears, it is gone completely like flipping a switch. It will come back if I kill it and let it set a while. Hope you can help, I'm stuck. Thanks, DJ
Answer -
It does that because there is air in the STC oil manifold.There should be a check valve in the #8 line between the STC valve & the manifold.If not you might have to get one.I cant remeber if you can clean them or not.The check valve is like 3-4 in long with a directional arrow engraved in the side of it for flow.
OK, thanks, I ran out to check the check valve and it doesn't appear to have one. My manual indicates where it might be, it's not. My STC valve is at the back of the engine instead of midway and the line goes staright to the manifold. I will look into getting one. One thing bothering me, would air cause a dead (with white smoke)cylinder? The exhaust stays cold on these cylinders. I don't think they would ever fire off if I didn't hit the throttle or shut off and restart the engine. Would air stay in the line indefinitely? Thanks again for your invaluable service.
Answer The injectors are mechanical.The oil flowing to the injectors is what advances the timing when fuel pressure is lower than 50 PSI.When fuel pressure reaches 40-45 PSI the valve shifts & dumps oil to pan through the fitting in the side of the block.You can mount the check valve before the STC valve in the main oil line(the #8).The white smoke is because the fuel is injected late & not burning correctly.The air gets out when the valve shifts.
