Injector Problem?

[Lin]

We just returned from a trip of a total of about 280 miles.  It seemed to me that all was running okay.  However, when looking at the engine today, I saw that an oil leak, probably from the valve cover, had left a coating on the right-side, far forward part of the exhaust manifold.  Since it would seem that the manifold should be hot enough to burn away such residue, I wondered whether that cylinder was firing.  I ran the engine at high idle for a few minutes and check the different ports with an IR gun.  That last port did not seem to be heating up like the others.  The manifold there was heating up, but my guess is that it is from conduction.  What do you think is going on.

[OneLapper]

If the injector is still squirting fuel into the cylinder, then the problem may be more likely a lak of compression to ignite the fuel.  I'd pop the valve cover off and check the valves and their components.  You can run the engine without the valve cover on to make certain that all the proper parts are moving, then check the valve clearance on the bridges.  If either one is excessive, you may have a stuck valve.  That will prevent compression ignition of the fuel.

Mark

[lloyd]

If you had a cylinder with low compression, low enough not create heat, then it would smoking a blueish haze. You can push down on the injector spring retainer with the engine running to check for a misfiring injector. But you have to really listen because it fires a cylinder every 45 degrees- for a 8 cylinder.
Lloyd

[buswarrior]

You got smoke out the exhaust? If not, fix the oil leak and never mind making trouble you don't have.

If a cylinder is missing, you'll see it in the exhaust. As you noted, you didn't notice any power problems.

You have to be really working that engine to get the manifolds hot, and you have to keep working them to keep them hot. On the idle, there's a whole cylinder full of cold air being sucked and blown, with very little in the way of fire going on to keep the engine spinning.

Sometimes that IR gun causes more trouble than it solves...

happy coaching!
buswarrior

[Lin]

BW,

Interesting explanation.  I remember, when I first got the IR gun, checking manifold temps.  I don't remember what they were, but I think it was in the area of 500 degrees.  Thinking back though, that was during the summer in over 100 degree weather after I just pulled off the I-10.  I did not consider that the engine temp on this run was way lower.  I did have some white smoke as start up today, but I think it disappeared quickly.  I'll check that again tomorrow.

Even if there is no firing problem, I will have to remove the valve cover to fix the leak.  I will look around, but I do not know what I would be looking for.  You never know though.  Sometimes obvious problems just jump up and wave.  Do you generally replace the valve cover gasket or would something like the Permatex gasket stuff be okay to use?

[TomC]

Lin- most newer valve cover gaskets are made of silicone-so you can easily pop off the cover when needed.  DO NOT use gasket sealer on it.  If it does have the old cork type gasket (that's really old), then upgrade to the newer.  But most likely it will have the newer silicone type.  Clean both edges off and just put a very thin fingering of oil on the gasket when reinstalling.  Good Luck, TomC