I have a 1991 NA with old style injectors. I do have a paper copy of the factory service manual. I had a rough idle condition and when testing it revealed cylinder #4 showing no injection. Coil was within resistance specs, spark plug new, and the injector has no "click" when turning the CAS. I hear clicks on all other cylinders. Using a logic probe, I checked the #4 connector and, when disconnected from the injector, I have one pole with constant power and the other no power except when I rotate the CAS and hear clicks on the remaining injectors. I do get a momentary light on that one pole when turning the CAS. I believe this tells me the signal from the computer is good? When I compare this behavior to cylinder #2 injector connector the behavior of cylinder #4 connector is the same. Once I plug in an injector (or 2 other test injectors that all show ohms within spec) and when back probing the connector I get both poles showing power and while rotating the CAS I get no click.

I am pretty confident someone on this forum can help me figure out why this is occurring !

Thanks in advance! I am new to this group and very much look forward to good things from this car. Once I get the car running better, I plan on replacing all the old style injectors with a brand new system but removal of the plenum is daunting at this point.

Grant