1. Join the Community!

    DSMtuners is a massive archive of DSM information - but more importantly, it's a COMMUNITY! Join in and participate with other DSMers, and invite all of your DSM friends to make this place their home. Chat with others, create a build thread, post questions and answers. Get involved! Logging in will also remove many of the advertisements, along with this notice. ;)

Resistance on ground circuit...

Posted by Ssm90gsx, Oct 27, 2020

Please Support STM Tuned
Please Support Fuel Injector Clinic
  1. Ssm90gsx

    Ssm90gsx Probationary Member

    10
    1
    Joined Jan 6, 2015
    canton, Ohio
    So upon having weird issues with my car (no spark on 1/4 and weird injector firing issues) I decided to backtrack and check out some basic things. The battery was relocated half a decade ago, and the engine bay was painted last winter. This brought the idea of a grounding issue. I verified all the ground locations were adequate as voltage drop tests showed me. Now here is where things got interesting. So I started measuring resistance between the negative terminal, and any given point with the key off, and had no resistance in any spots. I repeated the same test with the key on (ecmlink powered on) and there is a ton of resistance at the same points tested before with the key off. So anytime the MPI relay is activated, there is resistance on the entire ground circuit. About two months back, I had an MPI relay short out internally to ground, and it blew my MPI fuse a good 4-5 times before I realized what the issue was. I haven’t been able to trace out any issues with the mpi circuit, but I also haven’t had any luck with a complete diagram for a 90. So I had the car running a couple weeks back, attempting to get it dialed in on speed density with the new setup. I noticed while it was running, the tach on the dash was not reading correctly at all, but ecmlink logged it right. Also the car wanted to fall on its face when giving it big throttle variations, and no matter what adjustments were made to the throttletipin, the problem stayed the same. So after a busy week, I’ve come back to fire the car up to send out a log to someone more knowledgeable than I am, and the car wouldn’t start at all. With little diag, I realize my injectors are not firing while cranking the car. I don’t really know what to do at this point.
     

    Street Build 193  1

    1990 Mitsubishi Eclipse GSX
    awd · manual · 1G DSM
    Loading...
  2. 2Gjunkie

    2Gjunkie Proven Member

    88
    33
    Joined Aug 5, 2020
    Baltimore, Maryland
    Ground your negative terminal externally (while car is stationary of course) and see if that changes how it runs.
     

    Street Build 187  3

    1998 Mitsubishi Eclipse Spyder GST
    manual · 2G DSM
    Loading...
  3. motomattx

    motomattx Proven Member

    3,132
    1,109
    Joined Dec 9, 2010
    wampum, Pennsylvania
    Its not unheard of to measure weird resistance when you have voltage flowing through a circuit, the ground included. The battery should be grounded to the body and the engine block, anything ecu in or out should be grounded to the ecu grounds and not the body or engine.
     

    Drag Race Build 4K  10  24

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
    Loading...
  4. Ssm90gsx

    Ssm90gsx Probationary Member

    10
    1
    Joined Jan 6, 2015
    canton, Ohio
    The car is currently not starting and injectors don’t fire with the car cranking. The ground are verified to be good.
     

    Street Build 193  1

    1990 Mitsubishi Eclipse GSX
    awd · manual · 1G DSM
    Loading...

Share This Page

Support Vendors who Support the DSM Community
Boosted Fabrication ECM Tuning ExtremePSI Feal Suspension Fuel Injector Clinic Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications OHM Racing Raven Fabrication RixRacing RockAuto RTM Racing SouthBay Fuel Injectors STM Tuned Track Decals Track Sculptures VR Speed Factory