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Discussion Starter · #1 ·
Hi everyone i have a 2003 1.8vvt mx5 mk2.5
I recently have rebuilt the car from the shell and put the engine in and the car cranks but does not start! a month ago i realised the coilpacks were heating up to the point where the they were melting on one of the electrical plugs, tried several coilpacks and all the did the same thing, the other electrical plug was 100%!

so i tracked back to the ecu and cut the signal wire and ran my own wire to elimate a shorted wire, coilpacks still heating up so decided to get a ecu kit!

put the new ecu kit in and it stopped the heating of the coilpack but still no start also i have put two new coilpacks in and made no difference along with new spark plugs obvs!

i also triple checked the timing and its 100%! also found i wasnt getting a signal from the crank sensor so put a new one in and now im gettin 3.8v to the ecu along with the cam sensor which i think is okay??

took spark plugs out and earthed them and im only getting a spark when i cycle the key and try to start it again after that i get nothing! also after that spark i get nothing up the signal line from the ecu to the coilpacks

Also have tried a good earth from my own car to the engine of the mx5 and still made no difference

i have clarified with the person i got the ecu off and he says the car was running before he took it out so i know the ecu is okay!

Im really stuck and loosing my mind anyone any ideas on where i shud look at next thanks!
 

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Couple of thing shooting from the hip.
Fuel pipes the right way round ? Under inlet. Easy to get these wrong .
Are you getting the rpm needle fluctuating when cranking? If not would point to crank or cam sensor. Ecu is negative trigger for injectors and sparks. So 12v should be on all the time on both these looms.
Are you getting the 10secs fuel pump prime on ign 2?

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Discussion Starter · #4 ·
but wud all these things stop the ecu from sending a signal to the coilpacks to fire?? + have a new cam and crank sensor in and they are both sending a voltage signal to the ecu
 

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Its wasted spark so there are 2 negative triggers to fire coilpacks. Doubt you could see these with a meter. More likely a occiliscope. Best way is to pull a plug and attach lead and ground it to see if fires and repeat for all 4.

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Is the earth strap on nice n tight at ppf behind right rear wheel and the 1 on engine from exhaust cam area to bulkhead? High resistance will cause heat.


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I'm inclined to think the cam signal might not be getting to the ECU. I know you measured a voltage coming back from the sensor but that doesn't necessarily mean it's picking up good timing pulses from the crank pulley wheel. Did you set the gap between the sensor and the timing wheel teeth to about a credit card thickness?
 
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