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ecu not keeping power

gmp

Well-known member
Joined
Apr 1, 2007
Messages
549
Location
Denver,co
So I need your help...
For some reason my ecu is not keeping power when I turn to key "on" when I do this the mpi relay stays on for 10seconds then bam nothing. The check engine light doesn't come on when I turn the key to the "on" position either, this means the ecu isn't connecting right?
I tested this issue at the ecu pins 102 and 107 to find it killing power to these as well. I have constant 12v power to the ecu on pin 103.
But for the life of me I can figure this out?

As well my fuel pump isn't kicking on when It cranks. Ive changed ecu and mpi relay and still have the same result.
Also does anyone have the mpi pinout?

thanks for the suggestions

Toybreaker please chime im sure you have my answer
 
Last edited:

gmp

Well-known member
Joined
Apr 1, 2007
Messages
549
Location
Denver,co
ha never any takers on electrical questions here ha ha..... /ubbthreads/images/graemlins/devil.gif toybreaker the only one that's had to figure out mitsu electric problems that I really doubt. im pretty savy but was hoping someone could come in with a fresh mind; welp in any case im going to try a whole new engine harness and see if that remedys my issues for now..
 

toybreaker

iconoclast
Joined
Apr 30, 2006
Messages
3,581
Gary,

Sorry I missed this, been pretty upside down recently.



Sounds like you have a wiring issue.

yeah, that's right, a wiring issue.

























bam there it is /ubbthreads/images/graemlins/rofl.gif












Is this a swap?

What year ecu you working with?

Has this set-up ever worked, or are you still sorting it out for the initial start-up?




... "sounds" like you may dropping power into/at the mpi relay. /ubbthreads/images/graemlins/dunno.gif

Checking for power at the mpi terminal #10 (back/red wire) *may* tell the tale.

That should be live 24/7, and turning the key on shouldn't drop the voltage much.

If the voltage drops/goes away, you may be having issues upstream.

You can also check mpi terminal #3 (black/white wire) for voltage. Should read ~battery voltage with the key "on"


Check the fuseblock that's on the positive battery terminal.

(disregard the 6awg wire on the far right, I used this terminal block on a different project)

Because of their proximity to the battery, (and it's corrosive gasses) those fuses can develop corrosion on their legs and drop enough voltage to give some weird problems.

.. they also get abused during battery re-locations (and other wiring sins)

... So, they are one of the first places I look to/work thru when facing power supply type problems


The push in 20 amp fuse (with the black/red wire) coming out underneath is the mpi fuse.
It pretty much feeds the whole shitaree (thru the mpi relay), as far as the ecu/everything on the fuel side goes goes, ... (except the fuel pump) ... so any corrosion/problems there there will drag the whole ecu/engine compartment systems down.

The other push in fuse ( 30 amp) is the ignition switch/system fuse.
It feeds the white wire underneath, and that heads down to the ignition switch
With the ignition switch "on", power goes out (on the black/white wire) to the ignition coils/power transistor and down to the mpi relay ...where it feeds the fuel pump leg of the mpi relay ... (black/white wire, pin #3)

(yer symptoms suggest looking into ^^^ this ^^^ area, start to finish ... most diligently will pay the greatest dividends.



Starting at the beginning makes the most sense if you have a problem with supply side voltage.

To service/clean the fuse terminals, disconnect the battery negative terminal, and set it out of the way (so it can;t flop back into contact with the post)

Remove the positive termminal, and pop out the push in fuses (20 and 30 amp ones)
Wire brush the fuse legs (or just pitch 'em if they're at all green/corroded), and then brush/clean the terminals down in the block as best as you can. The terminal side of the fuse block is just a bus bar, but you can remove the individual output side terminals (non bolt in ones) by tweaking the lock tab visible down in the housing if they are questionable and/or you want to mix/match a new terminal block from yer pile o yard bits/tortured remains of 213.

... well mayhap I wouldnt run anything of an electrical nature from that cursed beast /ubbthreads/images/graemlins/devil.gif





Remove one wire set at a time, and wire brush the wire terminals.

Remove the fuse and wire brush the fuse legs as well as the bolts themselves to get as much continuity as possible

*note how many wires go to each of the bolt in fuse legs, and be sure to get them all back on the same side/where they belong!*


Re-install the thru bolts and make sure they are good and snug.



While you're there, remove the stack of cable ends/wires that also goes to the top of the positive battery terminal and brush/clean both sides of them where they stack against each other to enhance their continuity as well.

Re-install everything, and see if that helps.


You will probably working down on the mpi relay a bunch, so a diagram of the mpi relay posted to this thread would be a big help, if someone could be so kind. (I'm working off of old notes here)

Thanks!
 

gmp

Well-known member
Joined
Apr 1, 2007
Messages
549
Location
Denver,co
ok so got it running again, was a popped fuse on the under hood fuse box. A 40a that runs the defogger why that effects the ecu is beyond me?
Now I need to figure out why shes running super stinky rich...
 

gmp

Well-known member
Joined
Apr 1, 2007
Messages
549
Location
Denver,co
john finally got it running strong still rich but running so finally!!! It was traced back to a faulty cam angle which I remember you discussing that with me.
That black top is now smashed in the trash /ubbthreads/images/graemlins/devil.gif

Hopefully can finish in time for the big meet the 9th maybe maybe fingers crossed
 
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