94vvt swap crank but no start

Hi everyone I have a 1994 Miata with a 2003 vvt swap, has the entire harness from the 2003 so the car is pretty much an nb in a na's body. It ran fine and wonderful until I was dumb enough to lose the key, and as we know the 01+ has an electronic chip in the key that communicates with the ignition and sends a signal to the immobilizer which then allows the ecu to send spark. So I bought a 2003 ecu/immo/ign from a forum member he said it worked fine when he pulled it i believe him. Well when I put the new setup in the ecu wouldnt do anything and appeared to be dead, it only cranks but no fuel pump (i have a carter 255lph so you can hear it when it runs) and no spark. I grabbed the old ecu plugged it in and the the fuel pump came to life, but because of the immobilizer the old ecu will not send spark.

Why would the new ecu show nothing no dash lights no fuel. EGI relay( shows continuity and clicks on with old ecu)


So I thought it could be the new ecu so I had a friend bring over a known working ecu/immo/ign setup and his ecu did the same as my new one..


I have read that the 03 can be finnicky if the battery is less than 12.9v., but no ecu signal at all.


Keep in mind I have had an obd2 reader on all three ecus and the only one to read is the old or original ecu, the new 2 appear to be dead/no power.

hello, why don't you try to re-charge the battery after so many attempts it should be low. Second, since you have a handy friend and you already know you have fuel remove the spark plugs, and with the help of a flashlight look inside, inspect for fuel odors, check for fuel on top of the cylinder, your car may flooded. it will not start unless you dry the plugs and all that fuel is evaporated. the last thing you can do is to ground one of the park cables to see if you have spark, if you do the car will start but ONLY AFTER YOU CLEAN the plugs and the piston chamber is clear. to repeat the process.

RECHARGE THE BATTERY
MAKE SURE ALL THE ELECTRONICS MODS ARE CLEAR
RESET THE ECU
REMOVE SPARK PLUGS AND CLEAN THEM
INSPECT CYLINDER CHAMBER, THE CAR MAY BE FLOODED.
INSPECT THE FUEL PUMP IS OPERATING.
GROUND SPARK PLUG cable TO SEE IF YOU HAVE SPARK.

If all the above passed the test, Your car should start after this

RECHARGE THE BATTERY= took the battery out of my 91se had 13.1v (still no ecu power)
MAKE SURE ALL THE ELECTRONICS MODS ARE CLEAR= only electronic mod is the wideband, just the gauge is wired for power from a switched 12v(this was in the car before I lost the key so I've ruled it out.
RESET THE ECU=left the ground cable off for a bit.
REMOVE SPARK PLUGS AND CLEAN THEM=no spark as the ecu won't even turn on.
INSPECT CYLINDER CHAMBER, THE CAR MAY BE FLOODED= not flooded but still smells of fuel.
INSPECT THE FUEL PUMP IS OPERATING= I originally thought it was the pump so I bought a carter 255lph it works only when I plug the old ecu in with the new ignition and immobilizer, because they dont match it wont send spark.
GROUND SPARK PLUG cable TO SEE IF YOU HAVE SPARK. = no spark


Hyper, thanks for the troubleshoot list.

is a pleasure, NO SPARK seems to me you have an ECU issue, other things to check "although unrelated" is MAF sensor perhaps CAM or crank sensor. Most important, check if the crank sensor is dirty, like full of dust/oil. sometimes the crank sensor moves a little bit and the car won't run, you have to check if the bolt if is lose, too far away from the crank wheel and if is dirty it won't read signal. The distance from crank sensor and timing wheel is about credit card thickness. That's it.

one last thing when you are 100 percent sure your car has spark. FlOOR the car, ignition switch crank it, on for the engine to rotate freely. If it attempts to start or if you hear it trying to keep keep flooring it., after it does, let it sit for a while to clean the piston chamber from all the extra fuel. I bet half your problem is that the engine is flooded, the car will not start EVEN after you have spark. You have to floor the car, bro no mercy.

I was thinking the reason for no ecu power was an intermittent egi relay the big green one in the engine bay fusebox. I bought another replaced it and still nothing. Been reading up on 01+ ecu power issues and I haven't found anything to solve the issue.

bro put the car back to stock, with 94 factory harness and forget that VVT shit!

I know I have it all too, I just love how quick the car was with the working 03 setup.

Quote:

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Originally Posted by Weeblewobble

I know I have it all too, I just love how quick the car was with the working 03 setup.

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bro, is best you keep the 94 hardness then with a plug and play megasquirt you can control the vvt. that's your solution right there, plus you will propably be able to get more power after some tuning too

I already have a mspnp for the 94 so it all should fall into place. I decided to try plugging in the old pcm (the original 2003 that was in the car before I lost the key). As before everything came to life, the fuel pump wining and just no spark because immobilizer. I just cant grasp why the 2 new pcm's wont power up, but the old one will..

I'm thinking out side the box. You have three variables, one the old cpm original 2003, one harness, and two new pcms with primary problem no spark. you need to check the schematic for the three pcms and find the leads for each cpm that sends the signal to generate spark. the harness is the problem most likely, it is not wired correctly to generate ignition apark to the old unit, and not correct to power the new cpm units.

This thread is old, hopefully you solved it by now... I ran into the same issue. At some point there was a switch from using the key to power up the main relay to using the ECU. I am not exactly sure when this happened. It shows up in the 2003 wiring diagram, but not in the 2001 wiring diagram. There were also some changes to the emission controls FWIW.