Jamie Treblas

Hi, Thanks for the help! The 502's are serpentine belts,the ECU's have about 150 hrs on them, I tried checking the fuel injectors with a pressure gage, the pressure seemed to drop off within 2-3 # of each other. The cross over system was added about 50 hrs ago, We did find exhaust leaks around those cylinders. Jamie

Cord

iTrader: (2)

Check your injectors, you proably have a bad one.

Bob280Silencer

Remove the injectors(all of them)Number them upon removal,Bring them to an injector shop & have them flowed.That will give you a base line.If they're all good then you can look elsewhere.It would be quite strange that both #6 injectors are bad.ECM are set for a certian inj. timing on all inj.,can't do just one.Good luck!BOB

H2Xmark

a couple idea's that might help out if you are a little hot and are lean is one heat range colder plug plus most of the VST 454's and 502 mag mpi's had a 36psi fuel regulator installed if so then swap it out for a mercury 43 psi fuel regulator the part # is 806808A2
good luck
Mark R

Reed Jensen

What do the Spark plugs for those #6 cylinders look like? Do they show signs of detonation? (blistering on the electrodes, little balls of aluminum on them?) Also, When you get the motor back together periodically check those plugs and get a magnifying glass and peer all the way down along the ceramic insulator and look for an ash ring near the bottom. If the cylinder is running lean you will notice a difference between the plugs from different cylinders. Ash ring versus no ash ring, but plugs have to be new and only run briefly and then checked. Good luck, I know problems like this are like chasing gremlins. They come back to haunt you. Also, Going to colder plugs may help if the engine is held on boost for a long time. I'm assuming it is supercharged. If one plug gets overheated and the tip begins to glow it will pre-ignite the mixture and cause problems. Check those plugs for blistering.

mcollinstn

His plugs are bound to look like a christmas tree glitter ornament - he's got holes burned thru the slugs.

I did read above that the motors are NOT supercharged, just some minor bolt on upgrades.

With this in mind, running stock compression and nothing fancy, stock heat range plugs *should* be just fine for the application.

I also don't believe that the ECU is capable of different injector timing for a particular cylinder but could be mistaken.

As far as looking at the plugs, I am more interested in knowing what the OTHER plugs look like. We are pretty confident that #6 is/was detonating, but we don't know if it was at WOT or during cruise. We also don't now if the other holes were burning correctly or if they were lean or overadvanced. I'd certainly like to be able to stare at a fresh set of plugs out of it after a hard pull..

Jamie Treblas

Bob280silencer Thanks for the response, Do you know of a injector shop, if so can you give me there name and address Jamie Treblas

ursus

The injectors are hard wired together in parrallel in 2 banks of 4 on the 454/502 merc engines and so it is not possible for the ECU to have different injector timing for a particular cylinder.

Bob280Silencer

JT,There's got to one closer than New Orleans.Ask a local speed shop or carb shop BUT,if you strike out give me a call 1.504.486.7070 weekdays and I'll hook you up.Good luck,BOB

blownboat

Reed stated that the number 6 cylinder runs hotter on big blocks , I have heard this also. So maybe both motors ran lean due to regulator/pump/programming issues and those were just the first cylinders to go because they run hotter. Just a thought