Hey guys, I have a 1997 dodge ram 1500 with the 5.2 that I have some issues with, I did post about it in a different thread, but I have some new discoveries with it that I’m not sure are all related or not. I’ve had a misfire on cylinder 4 for a long time, I recently did a compression check and the cylinder is very low on compression, about 30 psi. I then did a leak down test with the cylinder at tdc, with 95 psi going into the cylinder, only 15 psi was holding in the cylinder. With the rocker arms pulled off, I supplied the cylinder with 100psi, and it held at 84psi. All the excess is going out of my the intake. I also have low oil going to the intake rocker arm on cylinder 4, maybe half the amount of the rest of the rockers. Could this be a failing lifter? With the valve cover on I also hear a slight squeak or chirp coming from the valve cover area. Do you think these issues could be related? Or just a coincidence that I might have a lifter going out of the same cylinder that a valve isn’t fully closing? I hope this all makes sense, any help would be appreciated, thanks.

 

If you put the rockers back on, does your leak down spike again? If so, I'd say you have a stuck lifter. Might be able to free it up with some variety of top engine cleaner..... but, I wouldn't hold my breath on that.

Have you fixed your plenum yet? Is your truck using oil?

 

I have fixed the plenum, maybe 5,000 miles ago, thinking that would fix the misfire. The truck does not use oil. Even if the rockers are on, with the cylinder at tdc shouldn’t the valves be fully closed whether there is a stuck lifter or not? I can see why a stuck lifter would keep the valve from fully opening, but it shouldn’t keep it from fully closing, right? With the rockers off, is 15 psi of loss acceptable? If not that should rule out a bad lifter and I would lean to think of a bad valve or valve seat. I am out of town for a few days so I’ll have to wait to try it again with the rockers on. I wish I pulled the rockers off a good cylinder to see what the loss was on good one if any.

 

With the rockers off and engine running. All the rockers seem to have the same range of motion, even the one getting low oil.

 

Not sure if you would be able to see if the difference in any event.....

If the cylinder is in firing position, then yes, both valves should be fully close. Yours aren't though, the intake valve is hanging open, but that problem goes away when you pull the rockers. Do I have that right?

If I do, then, the lifter is stuck in a condition that doesn't allow the valve to fully close. They are hydraulic, after all..... thus, have a range they operate in.

 

You are correct, I think. When I pull the rockers off, the problem definitely improves. What I’m not sure is when the rockers are off, so the is no question the valves should be fully closed, is 15psi of loss acceptable? Is so, a lifter problem makes sense to me, if 15psi of loss is too much then I would have to think a problem with the valve or valve seat.

 

According to industry standards....... Up to 25% leakdown is considered 'acceptable'...... and all cylinders within 10% of each other. (so, if you have on cylinder at 25%, and the rest are all 10%.... that's a problem.....) I don't like to see more than around 15% or so. But, that is on an engine with reasonable miles, and in good condition otherwise. And, given the age of these trucks.... Yeah, I am thinkin' 15% is darn good.

 

Ok that makes sense. Do you think the lifter could be over pumped or expanded not allowing that valve to fully close? I don’t know if that would make sense since it’s getting a lack of oil flow. The only other thing I could think of is if something might be stuck in the lifter bore not letting it go all the way down. I think I’ll just have to tear the intake off when I’m back in town.

 

Yeah, I suspect the 'fix' here, is going to be tearing it down, and replacing at least the one lifter...... Since it is *only* one, might be able to get away with just one...... but, if you have the cash, I would just replace them all, call it a day. They all live in the same environment after all.