All posts for the month August, 2023

After a year of frustration trying to get the EFI to work, I decided to go back to basics. I removed some of the EFI components, such as the throttle body, and pushed aside and secured the wiring. Then I rebuilt the Demon carburetor and installed that.

The engine still refused to start after resetting TDC. What I got was a backfire through the carburetor.   My guess was that the air/fuel mixture was collecting in the intake manifold and getting lit by a spark plug through an open valve. But that shouldn’t happen if the valve train is operating correctly. I removed the valve covers and checked to make sure that the valve train is operating normally — seemed alright.

I posted the problem on the Forum*.  One of the experienced members agreed with my analysis and suggested this solution:

“You are correct, backfire is usually produced with spark happening when a valve is open. That can happen if adjacent spark plug wires leak, your distributor cap could have a carbon trace, your timing set is off a tooth, etc. Let’s start at the beginning with the key OFF…

  • Remove your valve cover to expose #6 rocker arms and remove your distributor cap.
  • By hand, rotate your crankshaft via the damper bolt. When #6 exhaust valve is nearly closed AND when #6 intake is just beginning to open, right there when both rocker arms are dead level, STOP. (Use a straight-edge on your rocker arms.)
  • Look at your timing marks. They should be at TDC and your distributor rotor should be pointed at #1 spark plug tower (“1” is normally molded into the cap).

Notice that #1 and #6 pistons go up and down together. When #1 is firing, #6 is on its exhaust stroke (look at your firing order).  If the cam timing is off, your damper’s timing marks will show which way and how far it’s off.
If your distributor is off, the rotor will not be pointing at #1 spark plug tower. Remove the distributor and reseat it properly.  At about 6-degrees BTDC on your timing marks, your points should open. Rotate the distributor until the points just start opening. Here, you can use a continuity light. This will get your engine running. You may fine tune with a timing light or vacuum gauge afterward.”

He was correct in that the distributor alignment was indeed off a tooth.  After performing the above procedure, the engine started right up.  Hallelujah.

The plan is to get some enjoyment from actually driving the car.  After a few months, when I’m sure that it’s running reliably, I’ll take another shot at the EFI installation.


Hwy Thunder

*I highly recommend the Forum for any classic Ford owners!