I just put in a jspec S5 engine into my S4 TII and it won't start. I used the high impedance injectors and harnesses and spliced the harnesses into my S4 wiring harness. I also unplugged the resistor pack and bridged jumper wires from the center terminal to the 4 outer terminals. I'm sure that its not a fuel problem, you can smell the gas after trying to start it for awhile. I also put on my S4 TB. I didn't swap front covers, because I plan on running premix. I think its an ignition problem. Could it be the S5 crank angle sensor not working right with the S4 ecu? Anybody have any ideas?

 

The AFM is different from S5 to S4

 

I take it that it cranks good...thats a good start...





The CAS are the same...so that's not it. Check if your getting spark..pull a plug out and lay it on something connected to the block(for a ground) and have somebody crank the motor to see if it sparks...worked for me..



...timing may be off too if you find it is getting spark...