97 chevy k1500 p0303 misfire

@db4690 Thanks for the clarification!

On Rockauto, it states OEM part- coil on plug but if you look closely, the coil does not look like a COP, it looks like a single, main coil.

I’m not discounting the possibility it isn’t related to the rebuild or some other compression related failure but I like to rule out the easy stuff first. If it has a single coil and spark plug wires, it must have a distributor cap, right? Don’t see that on the list of parts replaced…that’s where I would be looking first…

If the compression and fuel pressure turn out to be red herrings, focus on the ignition system. Does this engine use a conventional distributor with a rotor that goes round and round inside the cap? If so, pull the cap and look for carbon tracking on the inside, and on the rotor surfaces. Everything ok inside the cap? Then run the engine in a totally dark area, see if you can see any sparks forming around the high voltage wires. Still a no-go? Then you have to start changing stuff around, see if the problem follows what you changed or not.

Thanks for the replies everyone . I’ve been busy at work. my Haynes manual says 150 psi is normal compression. with a maximum variance of 20 psi. Fuel pressure 60 to 66 psi. As far as a seal being the issue, all seals were replaced at time of rebuild (less than one year ago) also i am not burning any antifreeze,

seems to be fuel related to me just wondering if opening the intake manifold and replacing the #3 injector sounds like a good next step, i just cant really think what else could be causing a consistent misfire on only cylinder 3


you’ve got the “spider” fuel injection, as you are aware

If #3 is indeed bad . . . and can’t be fixed by hooking up the cleaning solution . . . just replace the whole fuel injection unit

But I’d want to be 100% sure, and that involves a proper diagnosis

right, when my brother and i rebuilt the engine we tore it completely apart every single seal is brand new, every seal. many of the old tired parts are new as well including the distributor

im just leaning toward leaking fuel injector because the fuel pressure is so low, indicating to me there is a tear or small hole in that injector resulting in insufficient fuel delivery to #3 and a decrease in fuel pressure

Your Haynes manual is wrong. Chiltons manuals are often wrong. Even factory service manuals are wrong.
Those manuals are put together by people with no clue or they’re recycling erroneous info into their own publication.

That being said, if this is a dead miss it can be sorted out to some extent although the underlying problem of low compression is still present.