the dreaded chuffing sound

[idibeast]

Hi guys the old money pits acting up again. A few weeks ago my 1985 6.9 ran low on oil. I left the truck sitting for about two weeks until I got around to changing it. Last night after getting the oil in, when I started it up I heard a kind of chuffing/ popping sound from the exhaust. I am wondering if this is from sitting or it there a valve problem. Thanks guys.

 

[f-two-fiddy]

More than likely, valve guides.

 

[hesutton]

That sounds like an exhaust valve is sticking, letting compression leak past it into the exhaust. That's not a good thing as it could kiss the piston and kill your engine. Time to pull the valve covers and have a look and listen. It can be difficult to assess play between the valves and guides with spring tension on the valve. But, if you pull the spring to check the valve, be sure that cylinder is at TDC, otherwise, the valve may drop down into the cylinder. Assessing the heads/valves is much easier with the heads on a table and off the engine, but I'm not sure how far you wanna go with it right now. If she is eating a lot of oil, that too may be a sign the guides are not up to par.

Also, compression test and/or compressed air (via the glowplug hole) may help you determine which cylinder is the culprit.

Heath

 

[idibeast]

Thanks guys shes not using a huge amount of oil but is definitely burning it. How do you go about pulling the springs?

 

[OLDBULL8]

Ya just don't go and pull the valve springs, the valves will drop down in the cylinders, then it's pull the heads. There will be two pistons at TDC on each revolution. You can only work on those two at a time, the springs have to be replace before the next rev., Get a set of valve seals before starting and replace them. To remove the valve spring, you have to compress it then remove the two little keepers.

Also if burning oil, you may want to clean the CDR or replace it with new. If the rubber diaphram is shot it will allow oil to be sucked up into the intake.

The engine rotates in a clockwise direction as seen from the front of the truck, and for every 1/4 turn of the engine(crank) each next piston will arrive at TDC. So, When the line on the vibration damper is at the 2 oclock position, cylinders 2 and 5 will be at TDC. When the mark is at the 5 oclock position, cylinders 7 and 6 will be at TDC, 8 oclock has cylinders 3 and 8 at TDC, and back to 11oclock, 1 and 4 will be at TDC.

Cylinder numbers are assigned 1,3,5,7 on the left (passenger USA) bank from front of truck to back, and 2,4,6,8 on the driver's side (USA), front to back. Firing order is 1,2,7,3,4,5,6,8.

 

[idibeast]

OK guys thanks a lot ill get started on it this weekend

 

[idibeast]

Hey guys I got the compression test done and all the cylinders showed 300 ( cold engine) except for cylinder 1 that showed about 170. Also before I parked her she had no power and constant black smoke, still sound like valve guides?

 

['94IDITurbo7.3]

Hey guys I got the compression test done and all the cylinders showed 300 ( cold engine) except for cylinder 1 that showed about 170. Also before I parked her she had no power and constant black smoke, still sound like valve guides?

squirt a small amt of oil into the low cyl and run the comp test again. if it comes up then it is rings. i doubt rings are the issue though, but best to cover your bases.

 

[idibeast]

OK I'm realy confused now, I got the passenger side head off but I can see nothing wrong. All the valves are sealing, not wiggling no burned valves. What now, I'm replacing the cylinder 1 valves,( showed low compression, not sure if gauge working properly) and all stem seals. Were do I go from here?

 

[CDX825]

From my understanding its also possible a lifter not functioning correctly will cause this.

I don't know about the low compression though?