Cylinders 5 and 6 not firing?

1995 FORD THUNDERBIRD
135,035 MILES • 4.6L • V8 • 2WD • AUTOMATIC
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SMERCER29
  • MEMBER
  • 1 POST
The compression check shows cylinders are fine. fuel filter, fuel injectors, spark plugs, and wires have all been checked. and a brand-new computer, alternator, and mass air flow have been installed. so I'm at loss of what is going on with it.
Sep 20, 2023 at 12:40 PM
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JACOBANDNICKOLAS
  • ✓Experienced Mechanic
  • 110,240 POSTS
Hi,

If you have spark to those cylinders and there is good compression, that leaves timing and fuel. Timing must be correct if six of the eight cylinders are working. So, we need to check if injectors 5 and 6 are getting power.

Each fuel injector will have a red wire and then one that is different. With the key in the run position (engine off), see if the red wires to the affected injectors have power.

If they do, connect a test light alligator clip to the battery positive. Probe the other wire at the connector and have someone crank the engine. Does the light flash on and off?

Let me know.

Take care,

Joe

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Sep 21, 2023 at 12:51 PM
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