View Full Version : FYI: Spark plug wire routing... don't be too neat!

06-25-2013, 11:10 AM
Last year as part of a general tuneup I put new wires on my 351W.

I thought that I was doing a neat job when I used zip-ties to separate and route the wires neatly parallel to each other.


However, I was then experiencing some random missing and noticing some funky off-timed flashes with my timing light. This was particularly noticeable when the engine got warmed up.

After some googling, I found this Ford TSB. Wires of sequential cylinders routed next to each other can trigger induction firing and touch off cylinders at as much as 90 degrees advanced. I am certain I was experiencing symptoms of this, even with my brand new Mallory 8mm wires.

On the 5.8 351W, cylinders 1 & 3 and 5 & 6 can be problematic. Please note that in the diagram below, they have #1 wire crossing at 90 degrees to #3 and #5 crossing below #6.

Since correcting my wires, my engine seems to run much better.



ISSUE: Engine miss, spark knock, buck/jerk, surge and other driveability concerns may be caused by induction crossfire. This occurs because of improperly routed spark plug wires.

ACTION: If spark plug replacement is performed, the correct firing order and spark plug wire routing is essential to prevent the possibility of induction crossfire between cylinders. Refer to the following procedures for inspection of the spark plug wire routing and firing order. Properly reroute the spark plug wires if required.

Whenever a high-tension ignition wire is removed from a spark plug, the distributor cap, or the coil to perform a maintenance operation, Silicone Dielectric Compound must be applied to the boot before reconnection. Using a small clean screwdriver, apply a thin layer of Silicone Dielectric Compound on the entire interior surface of the boot. Do not apply compound to metal terminals.


The firing order for 5.0Ls & all 5.8Ls is 1-3-7-2-6-5-4-8. On these vehicles the #1 and #3, or #5 and #6 spark plug wires must be separated to eliminate the possibility of an induction crossfire.

06-25-2013, 03:55 PM
Great find, fix and post!!!


john jones
06-25-2013, 07:27 PM
I will be working on this tonight! Thanks for the info.

06-25-2013, 09:20 PM
nice will have to check mine out

06-25-2013, 10:41 PM
Awesome find, and I copied your install last year. Will check it out on my boat. I have not noticed any issues with the engine missing - and I've never put a timing light on it.