AstonishingXJ

I'll try the pull a spark plug thing tomorrow and how do you do the thing with the timing light? I've never used one before.

red4dr

The plug wires, you just pull one at a time and for some people the noise changes or goes away completely since there is no longer a load in that cylinder, didnt work for me. noise was constant.
The timing light you just hook it up to the battery for power and then put the sensor on the #1 plug wire and the light will go on every time that cylinder gets spark. you will hear the knock on beat with the light, or twice per one flash. if it is one knock per a light then it should be in the bottom end, and since the head moves around at twice the speed, you would get 2 knocks per a light. That test was kind of hard to determine for me, since I have had one too many bumps to the head, i just saw a pretty flashing light....... my wife confirmed that it was once per a fire though :P

AstonishingXJ

So this will isolate it to the top end or bottom end, if it is in the head then what does that tell me?

DFlintstone

Btw. Pete. I baked it a little trailering a ton of bricks up my hill. Blew the lower rad hose, I now have a quick "rat, rat, ta,ta", on start-up sometimes. Less than a second. This is after a new Wix and oil change.

red4dr

in theroy this should show top or bottom end of you can distinguish a difference. as to where to go, im not sure, thats the step im on right now too. My next step is to pull the pan and check for play in the connecting rods, wrist pins or crank bearings. I also want to check to see if it is just timing chain slop since the noise was in the front of the motor for me.
hopefully the timing light might tell you something and give you an area to look in. I have one at home so it was a free step for me and it really just backed up what my time underneath it listening to sounds told me.

AstonishingXJ

Well I'll rent one from autozone or borrow one either tomorrow or Wednesday and give it a shot. If you find out what yours ends up being let me know so I can either eliminate that on mine or fix it!

I absolutely love this forum, I've learned/fixed/saved so much! You guys are great thank you.

DFlintstone

Dynamic Compression Test. (Dynamic meaning something is going on, as opposed to static). (At rest, or cranking for an auto compression test).

The basic idea of a "dynamic" compression test is you run the engine, usually at two RPM ranges, (two tests), and see how much the RPM drops when one cylinder is disabled. If pulling one plug wire on the dizzy doesn't change a thing, that cylinder is not working. That can tell you allot about the "health" of that cylinder. If it has a burnt exhaust valve or the rings are not seating, eliminating that cylinder will not drop the RPM's much. (or a pair together might be the head gasket).

That said, if there were a "real" rod knock, pulling the wire firing the plug igniting the blast causing that knock should quiet it down allot.

Lastly, the thing will zap you while you are pulling the wires off the cap. Idk if 40,000 volts could harm a pacemaker or not, but for most of us it's just part of the job. It helps if you first loosen the wires on the cap, put them in somewhat, then lift them one at a time while it's running, (off the cap)(where the spark comes from). If lifting one makes the knock go away, then you know more than you knew before. If you have a really bad rod bearing you might just leave that wire off.

Edit/added. Some say you should pull a connector off an injector. Same result, idea is you won't "rinse the oil", from the cylinder during the 5-10 second, test. (it's still being oiled)

AstonishingXJ

I pulled the plugs one at a time and it never made the sound stop but everytime I pulled a plug it misfired like it should. So every cylinder is getting the power it should, but when I tried the timing light thing I couldn't tell if it was one flash or two flashes maybe I'm just too slow! Haha

DFlintstone

Now there is a neat tip, seeing if there are two knocks per a flash or one.

EDIT, Oh! but the cam turns 1/2 engine speed. (so it won't open and intake valve on the exhaust stroke!)

In your shoes, since the sound didn't change pulling plug wires, I might pull the valve cover. Or listen up there really good with a hose to my ear or a stethoscope). Rocker pivot or lifter/push-rod issue?

JBimmolate

I had a noise similar to that when I got my 94 ZJ, Could not isolate the noise it stayed the same so I said F it and about 8 months later my harmonic damper came apart on me. Replaced it and now only has the small lifter tick that they all seem to have.

Miles

AstonishingXJ

How do I check if the balancer is out?

DFlintstone

Excellent Idea JB. For starters, just look at it. It's actually two piece. There is a strip of rubber between the inner and outer that sometimes starts to come out. You can also put a socket on the bolt, might be 3/4"-19mm, and see if it's loose.

red4dr

ya, I couldnt tell either so dont feel bad. it was my wife who said it was on beat with the light. I just went back to what i heard listening to the engine for an hour with the stethoscope.

red4dr

personally, my next step to see whats going on is pulling the pan and looking for anything broken then checking for play in the crank bearings, then pulling the caps to see if there is play in the wrist pins. Im not at all excited to start that project so i may just "let it develop" for a little while, while I get everything else changed out that I would like to and get it road worthy again.

cruiser54

If it looks anything like this: