So 2 years ago i bought a 1978 datsun 280z eventaully i got it started but it front fired and after takeing it for a drive one day after barely a mile it front fired alot was very delayed in accelerarion and barely made it home. It hasnt driven since. It has fuel it has spark, it has compression around 120 and its timeing should be in the ball park if it had fired before. now it just cranks over and over again not even a pop even when i spray starter fluid. I also put in an aftermarket programmable ecu called a megasquirt however that shouldnt be the problem because ive checked the wiring over and over and my labtop shows that everything on the ecu reads out so i was thinking it was something mechanical. I was told by someone else that in his car he had the same symptoms and it turned out to be the timing chain could that be it or any other ideas

Welcome to NICO Club! Fuel Spark and Air. You know you have spark because you've seen it visually by pulling a plug and watching it spark right? Same for your fuel, you've pulled the injector and watched the spray pattern on a cloth or something? Did you check the fuel pressure and make sure the filter isn't clogged? How about air? No vacuum leaks, throttle plate works, TPS in range? Since it's not running you can't view timing with a light, but if you haven't pulled the distributor, chain, cams or whatever affects timing, then it should be where it always was. Hmm, did it ever run properly? I suppose you could check the timing marks on various components and compare them to the FSM. We have those under the service manuals link at the top of the forum pages. You're not trying to use 2 year old gas are you? I'm a little suspicious of the ECU swap, but don't know enough about how it was done. If it worked before ECU swap and now it doesn't, well... We have quite a few Z guys here. Maybe they'll know something more specific off the top of their heads for you to look at. Good luck!

Yeah i visually watched the feul injectors spray fuel and saw that the spark plugs have a nice bright blue spark, there are no vacum leaks. Yesterday i put some gas directly in the cylinder and it still didnt even fire the ecu i have in is showing that tps is in range also to clarify the car stopped running before i put in the new ecu. I dont think it ever ran perfectly like i said it tended to back fire out the air intake. I asked about the timeing chain because im thinking it may have skiped a tooth or something.

Ok, so you put a megasquirt onto a non running engine? This is not the ideal way to do the swap, I've done two myself, both times I made sure the engine was running before I swapped everything over. Megasquirt on these cars is not a plug and play, there are simply too many variables unless you know what you are doing you should absolutely not swap onto a non running car. So if at all possible swap back to the stock ecu and you will have a lot less drama on your troubleshooting, then swap back to the megasquirt.