I removed my old gp from the rear passenger side cylinder (i believe #8). it was a champion and i am replacing with zd-9 that i purchased at autozone in western pa for .01 a piece anyways the old one came out fine, all intact, and the new one (motorcraft) wont fit. i even tried it in another cylinder and it fit fine, and the old champion goes back in with no problem. any ideas? Thanks

 

You mean the tip won't go in the hole or the threads won't screw in.

 

it goes in but gets stuck about a 1/4 inch from the threads, so i guess the tip isnt going in

 

Check the bottom of the hole for a tip stuck in it..........already. If there is nothing blocking the hole there could be carbon in the precup. Just be gentle checking the hole.... you DO NOT want to push anything into the cylinder. Post back when you find something...... You may want to read this first and bring cylinder to TDC on that piston.

The timing mark is found on a little plate that is on the front of the engine on the passenger side. The plate is mounted so it is very close to the main pulley on the lower front of the engine which is mounted on the vibration damper. On the side of the vibration damper, is a line, which when lined up with the line marked (O) on the plate, tells you that the #1 piston is at TDC(top dead center) You can see the line on the damper, and it points to the line on the plate with the (barely visible)O mark on it.You'll have to find a way to turn your engine over by hand (Crank/harmonic balancer bolt). Make sure you remove the power wire to the injection pump(so the engine won't start)and then rotate the engine until you can line up the marks.

The engine rotates in a clockwise direction as seen from the front of the truck, and for every 1/4 turn of the engine(crank) each next piston will arrive at TDC. So, When the line on the vibration damper is at the 2 oclock position, cylinders 2 and 5 will be at TDC. When the mark is at the 5 oclock position, cylinders 7 and 6 will be at TDC, 8 oclock has cylinders 3 and 8 at TDC, and back to 11oclock, 1 and 4 will be at TDC.

Cylinder numbers are assigned 1,3,5,7 on the left (passenger USA) bank from front of truck to back, and 2,4,6,8 on the driver's side (USA), front to back. Firing order is 1,2,7,3,4,5,6,8.

OK all the above is true...... to ensure the #1 piston is at TDC compression remove the inspection cover on the oil filler/gear cover. You will see a dowel pin from the IP if it is at 4 oclock that is TDC compression stroke, if it is at 11 oclock that is TDC exhaust stroke.......

 

i dont think that it is a previously broken tip, because the old gp will still fit in there, it looks like the champion has a little smaller tip in comparison to the motorcraft, but if it is carbon build up, what are my options?

 

Use a slightly larger..........than the motorcraft GP, extra LONG drill bit (so as not to loose it) and ream the carbon gently so as to allow the new GP to fit.

 

PLC7.3
Would that much carbon in the pre cup be unusual? Seems that would make the very tip of gp get hotter than the rest of the plug.