does anyone know how many pounds of pressure each cylinder in a 5.7 hemi is supposed to have? its an 07 if that matters. thanks

 

Most engines are above 150psi if that helps. and should be within 10% from highest cylinder to the lowest cylinder readings. You should take all of the plugs out when doing that and the engine should be warm.

 

ok dealer did compression test anf cylinder 6 is at 120 and cylinder 4 is 150 so not sure whats up

 

Did they do 2 tests or ran through it just once? You'd be surprised how much the numbers can change. Also, since the dealer is doing it, what was the problem you were having for them to do it in the first place? Have they done a leak down test to check the valves?
Those numbers aren't too far apart but are lower than they should be. A leak down test would be more helpful than a standard compression test.

 

Here 'dog, here is some background on his issue. As an actual mechanic, hopefully you can give this guy some help. We all know I'm just an old redneck off-roader... His problem is starting to get out of my league.
Thanks...

https://dodgeforum.com/forum/3rd-gen...th-07-ram.html

 

problems with 07?? wow....i've got one of the first 2006's...actually bought it November 2005...and 122,000 miles later...NO ENGINE PROBLEMS....yet...nock on wood. but i've only used 87-89 octane once or twice....usually i run 92 due to the programmer.

 

Did they actually pull the heads to look at the valves and seats???


Sounds to me you need to run some heavy concentrate of Lucas Injector Fuel Stabilizer. I'm willing to bet you've got a bunch of carbon build up on your seat in that cylinder and it's giving a low or rather false reading. I hope so for your sake anyways. The sound of clacking tells me maybe your valves are sticking. Pour some Marvel Mystery oil in your crankcase for a few hundred miles and add some Lucas Injector cleaner to your tank. Run the entire tank and have your compression check & leak down test re-done. I would also say maybe the coil pack for that cylinder is bad or there is a bad ground. Change the plugs too.

http://store.summitracing.com/partdetail.asp?autofilter=1∂=LUC-10003-1&N=700+115&autoview=sku
http://cgi.ebay.com/MARVEL-MYSTERY-L...2em118Q2el1247

 

thanks. i changed the plugs and coil pack looks good. figured it would run bad all day if it was a coil pack. not sure. ill all some lucas and is marvel mystery ok to put in? never heard of it. thanks everybody

 

dont know if it matters or not but....i run royal purple 5w20, and once or twice a month I'll throw in some "sea foam" into the gas......

 

Just beware of that Marvel Mystery Oil. I had a V8 once with only 140k on it and added some in the crankcase. It broke loose all that carbon buildup and it drained to the oil galley in the block and pluged the drain holes to the pan so the pump pumped all the oil to the top of the motor and none was getting back to the bottom. In the end I ended up with a bad knock with 2 spun main bearings and one destroyed crank.

On a side note, I agree with how Dirty said to do the compression test but when you are getting a big difference in numbers arent you also supposed to add a small amount of oil on the combustion chamber and then do the test again to help seal the rings and check for gap (blow-by) issues?