AEM smart coils no spark low voltage while cranking | AEM
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Last seen: 2 years 11 months ago
Joined: 08/30/2017 - 17:23
AEM smart coils no spark low voltage while cranking

Hi new to this forum looking for some much needed help to one of the issues I'm having with my Rx7.
I have a adaptronic select ecu for my 87 Rx7 t2. And iv had smart coils on it for about two years with no issues.
For some reason I'm getting no spark to my plugs but I am getting voltage while ignition is on.

but when I crank the engine the voltage drops to about 7volts which I'm guessing isn't enough to fire the plugs.
I by pasted the ignition switched battery voltage just to see if the coils were still working and
I took a wire directly from the main fuse 12v supply inside the engine bay and wired it directly to the smart coils and cranked and they all spark now ..
I did this just to see if they would work I can't leave it like this. Iv just replaced the ignition switch about a month ago.

But iv been having ground interference issues with my ecu sensor grounds which could maybe have something to do that??

For some reason while the battery is plugged up I get constant voltage to my injectors while there are supposed to only turn on when the car it's running
And also all of the sensor grounds from the ecu have a reading of 1.5-2.1 OHMS while they are supposed to be at close to 0.

If anyone has any advice or trouble shooting steps I could take to figure out what's going on I would Really appreciate it.

Last seen: 3 hours 7 min ago
Joined: 06/06/2014 - 09:31
General automotive EFI wiring

General automotive EFI wiring convention would be to not have the ignition power drawn through the ignition switch.  Normally, you'd have a main relay that handles the high current demands for the injectors and coils.  If you've already tested and found that bypassing the ignition switch power with main power under the hood to the coils makes them fire, then the absolutel first thing I'd do is use a relay to get power from the main power under the hood to the coils.  Really, this is more a question of how to wire and setup an Adaptronic ECU and doens't have much to do with the fact that you're using AEM smart coils.  Our Infinity ECUs get setup to always use a main relay.  Since you have an FC, I don't think those came with main relays and I don't know if the Adaptronic supports a main relay control - better that you ask them to be sure.  I'd say you have a wiring problem if you have constant power to your injectors.  Sounds like you need to revisit your wiring and install to sort some of these problems out.  

You didn't say exactly how you checked the resistance of your sensor ground wires but if you checked from the sensor connector ends to chassis or battery ground, I'd say 1-2 ohms is totally acceptable.  If you checked from the sensor connector ends to the sensor ground pin in the ECU connector with it unplugged from the ECU then it should be closer to zero but some resistance wouldn't be unexpected.


Last seen: 2 years 11 months ago
Joined: 08/30/2017 - 17:23
Well I'm not 100% sure it is

Well I'm not 100% sure it is wired threw the ignition. But I'm assuming it is because every time I came across info on Rx7 guys wiring them it's been threw the ignition. And the voltage drops while cranking. But iv ran a wire from the main fuse to the four wires that go to the coils. And I get spark now but it's still not starting
And now even worse I think I fried one of the coil packs. I was using my laptop to test the ignition by pulsing ign 1 & ign 2 to see if I was getting spark and I am now but it still seems kind of weak. I had one of the trailing and one of the leading plugs out of the rotor housing and the other two I left in at the time. Anyway as I was pulsing the ignition I smelled something burning. And realized it was the leading coil pack for the lead/plugs that was still connected in the rotor housing. And it was really hot to touch. I haven't messed with it since because i got very frustrated and walked away. Is there a chance this coil could still be okay or a way of bench testing it?

And yes I checked the sensor grounds using the chassis to ground. An I didn't know that that much resistance was okay. I was thinking that resistance was causing issues with my coil input or something. Now I really have no idea what is going on with these coils.
They have been wired the same way and working fine for 2 years now. So what could randomly cause them to stop working ??