coolant leaks from one cracked cylinder usually don't increase pinging

lube oil getting into a cylinder is the most 2nd most common cause of sudden pinging,
with a build up of carbon deposits in first place

off hand, some ideas about why the pinging would start suddenly would be:

valve stem seal has gone bad on one intake valve

broken oil control ring on one cylinder

missfire for any of many reasons on one cylinder
(where missfire is occurring the pinging happens on the next successful firing of that cylinder because the charge of air and fuel is greater than when the 'normal' amount of left over exhaust gas is present)

change of lube oil brand in past months
to one that is more prone to ping
(2 cycle synthetic oil is most ping resistant and racing engine builders sometimes use this trick to narrow down if the pinging is due to poor lube oil control somewhere)

there is a small chance that inside one of your cylinder head coolant passages some 'crud' has broken off and moved to partially restrict some important to cool spot ... the area in the center where two exhaust ports are side by side is one such spot

there is a small chance that maybe one of your ignition wires has shook loose and causing 'crossfire' ... this is especially a problem with #5 and #7

there is a small chance that your crankshaft position sensor is going bad

if you wish to 'track down' which cylinder(s) are pinging
the cheap 'fires in oil' sparkplug sleeves from nearly any auto parts store
can be moved around to each of your 8 cylinders.
A pinging cylinder will usually stop pinging when a sleeve is on that cylinder and slowing down combustion speed radically by mostly enclosing the spark

bottom line is that
if taking the SCT timing advance out
allows you to run without pinging
on stock settings with 93 octane
then at least one cylinder has changed
and you are not being fooled by some other similar noise

if you want more pinging ideas
here a very old post of mine on the subject:

http://dodgeram.org/tech/gas/Trouble/ping.htm

 

Hank and Aubrey,

Thanks so much for the help, advice, and the links.

Today on the way home from work the pinging was pretty severe and the truck actually bogged a few times when I stepped on the pedal. Rather than throw a bunch of money into testers and tools, I elected to take this one to the shop. If it is the fuel pump, I have no way of replacing it on my own as the tank was just recently filled and I have no where to hold 35 gallons of gas. Nor do I want to risk hurting myself lifting the bed on my own.

I'll let somebody else do this one.

 

it is surprisingly easy
to loosen the cargo box bolts on the passenger side
remove the cargo box bolts on the driver's side
then jack up the cargo box up to a 45 degree angle a little at a time
while watching the rear near the bumper for rubbing or hangups

this allows you to get at the top of the fuel tank without dropping the tank

when my fuel pump starting acting up
it did not cause pinging
just sudden engine dying without warning

 

Mechanic last night could not find the issue, He wants a crack at it with a cold engine so he kept it overnight.

I'm not 100% sure it is the fuel pump, but then again, I'm not sure what it is at all.

Last night the tech had me drive it home to drop me off and we pulled the fuel relay and turned it over to relieve the fuel line pressure. Reinserted the relay and turned the key to listen for the pump, it came on, but it wasn't the same noise I had been used to hearing, it was much fainter. It also came on 4 times turning the key back and forth. I would have figured it would have pressurized the line, kept the pressure there, and not reengaged. At least, not 4 times, but at this point I'm loosing my ability to rationalize symptoms explanations.

Tech did not think it was a bent valve as the idle was too smooth. He's also not convinced it's a compression problem either.

Perhaps this afternoon when I make it back over to the shop, I'll throw the programmer on it and really let her ping so he can hear it. I took it off in case they got crazy and started flashing the computer and erased my programming. I'm also not a fan of the "well then just take the programmer off" solution as it wasn't happening just a week ago on that exact same program. But if they can't get it to ping, I'll show him what's going on with the program hooked up.


One last question: A failing MSD box or coil wouldn't cause pinging, would it?

 

I've not heard of a bad coil or MSD to cause pinging.
I doubt it is your fuel pump now.
It sounds a bit like what mine was doing actually. Mine sounded like a ping to some people but it was different to me. Mine also puffed oil smoke during the winter. The noise was worse during the winter and especially on grades. I was topping out at 35 mph on some of the passes here and that's dangerous. I lost all kinds of power but a shop told me my compression was good. Someone thought that maybe a valve seal was bad and that's where the oil leak was and the rattle noise was coming from. It had 187k miles on her so I just went ahead and put a new engine in instead of trying to hunt down where it was and dumping more and more money into a tired engine.
Good luck!

 

Well,

Here's where I'm at:

Mechanic took it for the day yesterday. Could not get it to ping. He did find the coolant leak though. Freeze plug on drivers side of the engine. That's being replaced as we speak. He said the leak was pretty severe, and is worse when the engine's hot and being pressed on. He's not convinced this is the cause of the ping. I drove it home for the day and as soon as the engine got good and hot, it started pinging again.

He did dig up a spec sheet from MSD that states that optimal plug gap is .050 to .060 for anything below 10.5:1-13.0:1 compression ratio. The Dodge owners manual states compression ratio is 8.9:1. He suggested to at least try the suggested gap that MSD suggests and see what happens.

Well, I regapped them and after it heats up the pinging isn't gone, but it's much reduced. I'm starting to think it's definitely in the ignition system somewhere. I'm going to replace the cap and rotor just to take them out of the equation and test the wires resistance to verify they aren't the culprit.

I have the original coil from the truck and I'm going to hook it back up and take the MSD offline to try to diagnose if it's the MSD box or the blaster coil. I'll then reconnect the coil to see if it's not keeping up.

 

I hope you have good luck with the ignition system change outs

there have been past posts about MSD boxes drawing so much current that they damage the 'thyristor' driving circuit inside the PCM computer

intermittent missfires can cause pinging

 

I have heard that too, I hope I didn't hose my PCM. I should know more by the end of the day and will post up whatever I find. Luckily, I did buy the quick connect harness when I installed the MSD box and coil, so making the swaps should be quick. I'll also reduce the plug gap to .045 so I'm not over stressing the stock ignition system.

Thank you so much for your help Hank!

 

check the cap & rotor (or just swap them out)... use oem mopar on both.

I had a problem where it started pinging like crazy and it turned out the msd setup wiped out the accel cap & rotor. went back to mopar and it lasted alot longer.

 

No luck...

Cap and rotor swapped for new. All wires checked for resistance. The variance was between 91 and 172 ohms. That's still way better than a cheap set if I'm not mistaken.

Moved to .045 gap to make sure I didn't overstress stock parts testing ignition
Removed MSD 6A box from the equation....ping
Removed 6A box and MSD blaster 3 coil from the ignition system....ping
Bone stock ignition....ping

Here's where I'm at:
Cold engine: no ping, hot engine: ping.
99.999% sure now it's not an ignition problem.
No CEL's, tech couldn't find anything.
No more leaking coolant.
Tune it to 87 octane: no ping,
93 tune: ping.
Fuel pump checked out at 52psi steady.

Frustrating...

What's a good way to check fuel injectors to know if they are failing?

Maybe I'll try an old performance tune hemifever gave me before he tried to up the lower end.

Any other ideas?...I'm all ears!