Thread: Having some electrical issues... curious if anyone ran across this before...

I'm having a little electrical trouble, and can't seem to pin-point the problem. Curious if anyone else has ran into this, and if so, if they found a solution...


This involves my 92 240SX with an SR20DET running on AEM EMS:


I turn the ignition switch to the full "on" position to run the fuel pump (engine not running of course). And the tachometer jumps around 500 to 1000 RPM, bouncing with the fuel pump signal. Pull the fuel pump fuse, and it sits still. So far I've checked all grounds in the engine bay and the ECU, and everything is good there. I'm assuming it's a grounding issue. Tomorrow I plan to cut the fuel pump ground and ground it separately through the chassis (been meaning to do this anyways). If it's not that however, I'm out of ideas.


Any suggestions?

is this a series 1 ems. if so you have ground issues. after I put my ems in with the 24-1 trigger wheel i had some weird electrical issues. If i turned on my lights my pump would prime. if I touched the brakes the pump would prime. I did a little research and found the ems is very sensitive to grounding. 1) do not use the engine harness as a ground point. 2) do not ground after market electronics at the same point 3) make sure you have good voltage at the ems. I ended up redoing the grounds for the entire car and making sure I have good voltage at the ems and the problem was solved. I have a hyper ground system under the hood with a extra frame ground. I moved all of the gauge grounds and electronic grounds to different points. relocating the battery can also cause odd issues if its not grounded well. several other forum members have also had some of the odd issues.

It is indeed a series 1 EMS. Thanks for the tips! I'll move around some grounds today, and see what I can figure out, lol

yep series 1's have odd ground and voltage issues. They fixed these bugs in the series 2 but never released a firmware fix for the series 1.

guess I got lucky with my series 1. I didnt have this issue.

I've been working on it all day, and I just found that between the ECCS relay (pin 3) and the ECU connector (38 and 40 something) I was not getting continuity (this is the power to the ecu circuit). Which is weird, because the ECU powers on. I can actually start the car just fine. It doesn't run that great atm, but it does run. I checked the continuity from the relay and the engine/chassis harness connector E9/F8 and it was good. However, the circuit from that connector to the ECU wasn't good. So I think this "may" be my problem. Not sure how it runs without it, but I'm hoping I can get the issue fixed tomorrow :/

Figured out yesterday (finally!). It turns out that when I had the engine harness done back in 2005, that the people who did it had the ECU, o2 Sensor, and two other wires all powered off of one switchable 12V source. The ECCS relay wasn't actually doing anything! So I moved the ECU power back on the ECCS relay circuit, and everything works great now. Took a lot of continuity testing to find that one, ha ha.