Burning oil after new head install

[Rawze]

(01-30-2018 )IrishKW Wrote:  ...
Took a light a looked in down the cups, #1 looks like it is grianey on top almost like sand,
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Hardened "sand" on the piston crown is known as "fuel impingement'. - Its most basic explanation is that liquid fuel (or additives) is allowed to stay in the cylinder in liquid form long enough to settle / sweat (or drip from a leaking injector) onto the metal surfaces instead of staying in an atomized form. It is more complicated than that but that is the basic premise.

It can be caused by a lot of different things including a leaky injector, bad spray pattern, actuator issues, injection timing issues, bad fuel, using fuel additives, etc. etc.

If it is on only one or 2 pistons, then it is most likely an injector issue. If it is in all pistons, then it could be someone using fuel additives, it can be injection timing problems on a bad delete (very common), cam slippage, or other issues.

It can also be a coolant issue, where a leaky injector cup allows coolant to drip down onto the piston crown too... but this is usually accompanied by accelerated wear to the liner cross-hatching.

A tiny bit of impingement here or there on the edge of the pistons over time is almost to be expected as an engine gets a lot of miles on it due to cold starts, etc. - It is the nature of them, but it does not take very much of an issue at all to cause rapid problems within the newest engines. They are significantly more sensitive to impingement problems.

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This picture almost looks like someone dripped liquid metal down onto the the piston directly below the injector. This is a fine example of fuel impingement buildup due to a leaky injector...
   

-- Obviously, that injector is bad and needs replacing, regardless if it checks out ok otherwise.

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And here is one that had impingement problems due to too far advanced injection timing programmed into the engine (a bad delete program). In this case, ALL 6 CYLINDERS looked similar to this and this CM2350 engine was programmed to run about at more than +5 to +9 BTDC (before top dead center) in the mid-rpm band at its highest torque/fueling output. It also had as much as +11 degrees in its lower fueling regions, using EGR+timing settings without any EGR gas avail. any more.

The piston is covered in it because the injection timing was simply too high. It is also evident in the pic that fuel over-spray was getting outside the bowl and onto the outer edge of the piston. With injection timing that high, it has time to also settle on the metal surfaces and collect into droplets before it starts to burn... resulting in fuel impingement.
   

I.E.> An equivalent description of fuel impingement = When you are at the super-market and you stand there with the freezer-door open, looking at all the ice-cream.. that sweat and fog on the inside of the door building up is moisture Impingement. - Same thing happens inside a cylinder on the piston and other metal surfaces, if the temperatures are not right, or if the fuel is allowed to mix for too long.

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Fuel impingement buildup itself causes many secondary problems. As deposits build up, it increases the compression ratio of the cylinder(s) significantly.

With a high compression engines like a 2350 (18.9:1)or X15 (19+:1), it does not take very much of it to cause the combustion ratio to get so high that it eventually causes a head gasket and other failures.

Another common problem that fuel impingement causes is accelerated valve seat wear. The fuel impingement that gets into the valve seats, eating them up. Eventually the valves recess into the head so far that they can no longer be adjusted. That or a valve breaks off/cracks due to the vavle-seat area being worn out so thin. The result often destroys the entire engine when a piston strikes the broken/cracked valve.

- Again, this is extremely common in bad delete programming where some fool incorrectly decided that the "Alpha1, EGR+mapping" factory injection timing was ok to use after the EGR has been plate off. - This is an improper assumption and a BIG BIG MISTAKE on the part of the moron who made the program.

last but not least,.. the more modern an engine is, the more difficult it is to control and keep fuel impingement at bay ion the combustion chamber. This is due to both higher compression ratios and due to newer injection strategies and designs, where the fuel is more atomized, much higher pressure are sued, and the fuel becomes more volatile as a result.
(more on these injection strategies): http://rawze.com/forums/showthread.php?t...8#pid15548

Tags:

fuel problem, fuel impingement, crud on cylinders, sand on cylinders, bad injectors, timing issues