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ECM Failure; Are ECM's really bomb proof?
Topic Started: Mar 1 2015, 08:48 PM (1,887 Views)
Metromightymouse
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Powdercoat Wizard

If you haven't done it yet, inspect as much of the wiring between the underhood fuse and where it goes. Look for any areas where the wires go through sheetmetal. Check very carefully for somewhere that the wire has been pulled against the metal and it cut through the insulation or anywhere that might have gotten hot and melted through. If all of that checks out I have a 95 ECM that I will loan you for the cost of shipping if you want to check it before paying for a replacement. You just have to promise to return it as soon as you have a replacement if it is a bad ECU.
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randjw
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[ *  * ]
I have inspected the wires probably more than I should have I am going to have a lot of electrical tape work to do once I figure this thing out. I surely do appreciate your offer to send me an ECM to try but I should probably try to find one closer to me. If for some reason I can't I surely will pay for the shipping and return your ECM.
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Hanuman
"The Almighty Grounds Cleaner"

your probaly not going to blow a fuse with out the ecm.
the ecm provides the ground connection for many many circuits....(think of the ecm as a whole bunch of on/off switches)

with out the ecm in place, nothing is there to complete the bad circuit.
the ecm may not have been damaged at all.....its blowing fuses, this is a good sign, its not cooking the ecm!

your going to need to individualy go through each fuel/ignition circuit
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randjw
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I was wondering about that, I was thinking the same thing. I don't have any wire schematics, I have been using some that I found on-line thus far. Anyone know where I can find the schematics to trace these circuits?
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myredvert
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myredvert

Geo Metro Forum → The Garage → Factory Repair Manuals/Wiring Diagrams → 1994 library

There are wiring diagrams in the "Electrical Diagnosis" sections for each system, more complete schematics near the bottom in the "just 1994 circuits." They aren't the 95, but should be the same for virtually everything, and it's the best you have until you get a 1995 FSM.

Anytime there is an option for standard or Advanced Emissions systems, use the Advanced.
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Metromightymouse
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Powdercoat Wizard

Let me know if something doesn't match up and I will check mine for you.
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Hanuman
"The Almighty Grounds Cleaner"

geogonfa
Mar 2 2015, 06:36 AM
Just my $.02...follow the FSM and double check everything before replacing...might be the backup light switch, if it's bad or shorted it will cause the same problems... :type
have you checked this :gp
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Hanuman
"The Almighty Grounds Cleaner"

the tailight fuse supplies power to the ecm......
you mentioned the 15 amp under the hood......that is for the fuel injection.

lets narrow things down a bit.
remove the 15 amp fuel injection fuse....try and start (it wont, dont worry about this...just crank it for 10 seconds).....did the tail light fuse blow?
if no, unplug the injector harness (upper passenger side of tbi) and install the fuel injection fuse.......crank 10 more seconds.......did one or both fuses blow?
if yes, replace fuses and unplug the injector resistor, and plug in the injector......repeat.
did one or both blow?

this is effectively isolating the ecm, then the injector, then the resistor....keep in mind this will include wiring in-between circuit components.

.......................................................

because you were welding essentialy against the firewall, and i believe the injector resistor is located drivers side top on firewall............there is a strong possibility this is now fried and probaly has a unwanted ground on the firwall......the wiring is right there also........

but lets not forget, the injector wiring is known for having damaged insulation inside the tbi after 20 years...the welding may have created a short there also.
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randjw
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Just wanted to up-date everyone on my electrical problem. Thanks to a fellow Geo former (Metromightymouse) for loaning me an ECM, I now have a running 1995 Geo Metro. Turns out that the welder fried my fuel pump, ECM and blew the fuse in my stereo. I was without my Metro for nearly a month, will never weld on my car again without first disconnecting the battery and ECM. I believe that the cheep welder I was using didn't help either, Harbor Freight welder that arc's even if your not pulling the trigger. Thanks again Metromightymouse, it sure is reassuring to know that there still are good people out there who are willing to help someone out.

Thanks everyone!
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