Rough Runner

[MIKE_JAMES]

Truck no 1 is still running like a dream, now I have a problem with Truck no 2, its a 1985 K30 wiht the 6.2 diesel, started with a small ticking noise like an exhaust leak but less than 50 kms on it started to run rough and make popping noises out of the inlet manifold, I couldnt see anything wrong externally, this time theres no swirling or gurgling in the radiator or overflow but I cracked open all of the injectors while it was running and numbers 5 and 6 seem to make no difference to the way it runs, any ideas would be appreciated

[Brianlar]

Popping noise out the intake indicates the intake valve is not holding pressure, or the motor is severely out of time. Do a compression check, and timing check. Also try and run it without the valve covers on, and see if the rockers are all moving. That last one will be messy.

[MIKE_JAMES]

Thanks for that, will start with the compression test

[dieselbegreat]

For me, popping from the air cleaner turned out to be a broken rocker shaft and some bent pushrods. I would suggest pulling both valve covers to see what's really going on with the valve action (or inaction as in this case). Replacing those parts fixed it good as new.

[arveetek]

Exhaust popping through the intake manifold can also be indicative of a failed lifter or two. I just rebuilt my engine, and I had exhaust popping through the intake until all the lifters pumped up and started opening the valves correctly.

Another thought I had is the EGR passages in the engine. If it happens to be a C code engine with the EGR in the intake, then the EGR valve could be defective or leaking, allowing exhaust to pass through into the intake manifold. Or, if the EGR has been removed or blocked off, the intake gaskets could have failed or the plate used to block off the exhaust ports could have come loose or blown a hole through. However, if it is a J code engine with no EGR, then this wouldn't be a possibility.

Casey

[MIKE_JAMES]

So far have found one broken bolt holding the rocker arm and two missing pushrods!( No 2 cylinder) does not explain the low compression on 3 and 5 so will pull the heads and check further, thanks for the input