plug wire order

Well, swapped in a new f-head wire it all up, and try to start it but all it does is backfire. it ran a year ago when i got it. the plug wires were off and i put them on today in order 1-3-4-2 and in position on the distributor to match my 3B but it wolnt start. i think there is a way to tell TDC based on the crank pulley and some mark but i dont remember how. any ideas of where i should go and look to make sure i have them on the distributor right? (i checked spark at each plug and all is good there) Thanks, Geoffrey.

 

Did you pull the oil pump at any point? That can screw things up. The best way for me has been to pull the number one plug, and hand crank by the fan (or your wife turning the key in spurts - coil unplugged of course) and when you feel air pressure shooting out, you're on the number one compression stroke, aka towards TDC. You can actually look in the plug hole with a flashlight and get a perfect TDC by moving the fan blades ever so slightly.

The timing mark will probably show via a small notch or yellow paint (faded, no doubt) on the main pulley/case. However, that little yellow spot will typically be 5* before TDC. Scrape the cow crap and squirrel bits off a little more and there may be a scribe for TDC.

 

If I remember correctly, the plug wires on the dist cap, go on in a counter clockwise direction! That may be your issue or you are not at TDC on compression stroke. I could be wrong but I had the same thing happen a while back. Good luck!!

 

Correct, counter clockwise, i have that, same order as the f-head on my 3b and no dice

 

"when you feel air pressure shooting out, you're on the number one compression stroke.."

Then, pop the cap off the distributor and see if the rotor is pointed at your #1 wire position.

 

The distributor could be 180 degrees off from your 3b. When the oil pump is installed correctly, the #1 plug wire on the distributor should point to 5 o'clock. I did this on mine but then I replaced the distributor, which was keyed backward from the original. This made my #1 wire now at the 11 o'clock position.

 

The first task is to set the engine at 5 degrees before TDC on the #1 plug.

Assuming the engine was assembled correctly the mark on the crankshaft pulley will align with 5 degrees before tdc at two times when generating a spark-- once for #4 and once for #1 .

First, set the point gap properly.

If you remove the valve cover you can look at the valving and determine when #1 is approaching 5 dbtdc.

Turn the engine clockwise manually. Watch the #1 intake valve -- when it opens (rocker arm depresses the valve stem) then it is on the intake stroke. That means that the next time the mark on the pulley crosses 5 dbtdc that will be the correct position for the #1 piston and the point at which the spark is generated.

The timing marks on the front engine cover will indicate TDC and 5 DBTDC if you look carefully. The TDC mark is not relevant to what you are doing now.

Once you have set #1 at 5 dbtdc then install the rotor button and see which plug wire will get the spark -- that'll be #1. It is likely at 5 or 6 o'clock, but I've seen it at 12 o'clock and 11 o'clock.

You can static time the engine here by disconnecting the wire from the "-" side of the coil and connecting an ohmeter (preferably one with a tone) to that wire and the other side to ground. Loosen the distributor and turn it 'till the points close (0 ohms or a steady tone). Then turn the distributor CLOCKWISE 'till the tone stops or the meter reads infinity. The spark used by the F head is the one created when the points open, so you just set it so that the points will open at 5 dbtdc and you should be fine.

Now, if you changed distributors between the time it ran and now you could have created a new problem. There were two types of seemingly identical distributors used in the F head, but the relationship between the tang at the bottom end and the rotor button contact are different for each type by a few degrees. That will show itself in that you can't set the timing 'cause the plate under the distributor limits the range. This problem will be easy to solve, but it will require re-installing the oil pump one tooth more or less than it is now.

If you go to the CJ3B page you will find a very good description of this 'quirk' and a detailed description of how to fix it.