Missfire on cylinder number 3

[Conmanmc]

I have a 1996 4x4 with the 5.7 vortec. I just got done replacing the engine with a Chevy performance crate engine. The original threw number 4 rod out. The new engine got the fuel injection swap to mpfi, all new delco plugs, msd wires, msd cap and rotor. Finally got it put all back together and timed and it has a miss on cylinder 3. I pull number 3 plug and it’s not fouled and it doesn’t smell of gas. Then I moved on and shorted number 3 plug wire and the cylinders dead. I’m at a loss. Is the new fuel injection somehow plugged? Any input would be great.

 

[[email protected]]

Have you run a scan on the engine/ Like a snap on. I had this also and found out my brand new delco injector unit was bad. did not fire two cylinders and regulator did not work.
Sent it back got a new one and worked fine.
also run scan to check outside parts first, plugs, plug wires, cap .Just because they are new does not mean they are good. Today parts are not as reliable as they use to be.
Trust me I have seen it all on my last engine.
Take care
Skip

 

[Conmanmc]

I have scanned it. And it has a P0303 code and that’s it. I’m leaning towards a faulty injector. I was going to do a compression test just to double check the new engine. Thanks for your input!

 

[Enigma540]

I'd ohm the distributed cap and wires with a DMM first, just to rule out the simple things. Wouldn't be the first time an MSD part was bad straight out of the box. Then I'd run a fuel pressure drop test if you have access to a scan tool that can trigger the injectors individually. Do all the easy stuff first.

 

[Conmanmc]

Thanks guys appreciate the input. I ohmed out the cap and wires, everything checked out there, so I went and load tested the wiring back to the engine, and that all checked out. Just out of curiosity I had a extra ecm on the shelf, so I tried that, didn’t change a thing, checked fuel pressure and that checked perfect.. triggered the injectors one at a time and found number 3 would not fire, went and got another fuel injection set up and now runs like a champ!