Greeting all! I have a 1995 F-150 with the 5.0L engine. I was having problems with the fuel injectors and discovered it was a bad engine wire harness. I replaced the harness and injectors while I was at it. Now it will not start. Prior to the engine harness replacement, I was getting a big fat blue spark at the plugs but now it is a weak yellow spark. I replaced the ignition module, coil, wires, plugs, cap and rotor, distributor, computer, cleaned the grounds to the engine, new battery and battery terminals. With all of that...I still have a weak spark that will not ignite the fuel. HELP! Does the coil body/frame need to be grounded?

 

Stop changing parts. Put the original injectors back in - they NEVER go bad. What exactly was "bad" about the engine wire harness? Where exactly was it "bad"? Exactly which wires were "bad"? Do you still have the original harness? You should repair it and put it back in. Where exactly did the replacement harness come from? Put all the other original/previous parts back in that you still have since there was obviously nothing wrong with them. Post pics of the battery terminals. No, the coil does not have to be grounded to work properly.

You should put ALL the truck's details into your signature as this page explains:

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Where did you get the replacement engine harness?