#125348, "Ignition short" Apr-25-09 09:15 PM by thedawg
So I have a 95 ESi MTX. I did some mechanical work and bumped everything around, and now the car shorts out when I turn the key from ACC to ON. Voltage drop from 12.5v to 5v whenever the key is in the ON position. If I pull the "IGN SW / Moteur" fusible link (aka Ignition fuse), voltage goes back to normal.
I've disconnected the ECU, all sensors, all accessories (alt, starter), all relays, and all harness interconnects I can find in the engine bay. All that's left is the wiring between the front and interior fuseblocks, and chassis hard wiring. Still happening.
Also, no fuses have blown during this process. A lot of relays freak out and buzz off and on extremely rapidly when the voltage is low, but when the voltage is 12v they operate normally.
It's not the EGR pipe, I've lost two harnesses to that, but this one's not burnt or damaged anywhere I can see.
Anyone have any idea what portion of the harness I should look at to find the short? (What is powered by the Ignition fuse?)
#125354, "RE: Ignition short" In response to Reply # 1
Wow. That sounds like a real loving-life kind of project. Don't envy you there. If it's shorting to ground when turned to ON, I guess I'd have to start tracing down the harness from the ignition switch to the firewall. They *do* run along some stamped steel bits in the anti-submarine braces before reaching those main connectors under the HVAC controls behind the radio, right?
Good luck on that one. You've got the schematics, right?
#125426, "RE: Ignition short" In response to Reply # 2
Originally posted by DR1665 You've got the schematics, right?
Unfortunately, no.
The electrical manual widely available is for 97-99s and the section for ignition (see page 110/112 of 97-99Electrical.PDF) is corrupted/has errors.
I happen to have an original DSM Backup CD (have since sold my original paperback FSMs) which does have a 95-96 electrical PDF, but the portion for the ignition and engine electrical (section 8A) is completely missing.
I need 8A-56 "Ignition System" and 8A-32 "Starting System".
#125427, "RE: Ignition short" In response to Reply # 3
If it drops voltage I'd think it'd be a bad connection, as a straight short would pop the fuse. Try the radio? I know it's in an unrelated area, but worth a check. I'd check all the ground connections, as I had a poor battery ground one time, and it'd read 12V until I turned the key, drop to like 2V, eventually bleeding up to 12V over like a minute or two, then zero out when cranking. They'd be my first guess.
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'95 GS w/ t3/t4b FMIC, diy piping & RFL BOV MS2-Extra Fuel&Spark 50 lb/hr Holley injectors w/ 1:1 RRFPR JE 8.8:1 dish w/ Hastings Rings Eagle Rods w/ ARP bolts ARP Head studs Mild port/polish head 3" custom DP/cat section, 3" PIT catback dual MBC - 12 psi / 20psi
#125778, "RE: Ignition short" In response to Reply # 4 May-27-09 11:49 AM by thedawg
Originally posted by justins71 If it drops voltage I'd think it'd be a bad connection, as a straight short would pop the fuse.
Problem solved: The positive battery terminal was corroded internally. This was giving the car enough juice for the relay to energize, but as soon as it closed the high-amp side, power would cut out and re-open the relay, thousands of times a second. This created a buzzing noise from all the relays.
There are two pieces to the positive terminal- a lead ring and a brass insert ring. Using a terminal post cleaner on the terminals didn't help, the insert ring had to be knocked out and cleaned with a dremel. There was so much corrosion between the lead and brass rings that they were passing voltage but not amperage. I believe this is a bad design as no other car I've ever seen has an insert ring, and it has ridges which clearly make poor contact.
Clue #1: Voltage drops from 12v to 3v while using anything that required more than the (~0.3A) relay-opening amperage. (Headlights, starter, AC blower, horn, etc)
Clue #2: Hooking a 6-Amp manual battery charger to the steel outer ring of the terminal while the battery was connected gave enough amperage to run the headlights and other medium amperage devices.
Clue #3: Known good batteries didn't fix anything.
Clue #4: Even with all relays, fusible links, and fuses disconnected, not enough power to run any single circuit.
Outside of Corona: "That sucks, peace out..." (jamie walks away)... "Sweeet, what we doin?" -Zac Tim's garage (prior to motor install): "Im gonna smoke real quick, that way if you fuck up I am already nicotined up" -Tim
#125797, "RE: Ignition short" In response to Reply # 6
That was my issue here recently. First the ground went, but this time was the exact same thing. I would probe the battery and get constant 12V, but got the drop when I probed the pos connector. I cut off those double band-clamp craptacular pieces and put on a solid lead one with a stud. No more issues!
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'95 GS w/ t3/t4b FMIC, diy piping & RFL BOV MS2-Extra Fuel&Spark 50 lb/hr Holley injectors w/ 1:1 RRFPR JE 8.8:1 dish w/ Hastings Rings Eagle Rods w/ ARP bolts ARP Head studs Mild port/polish head 3" custom DP/cat section, 3" PIT catback dual MBC - 12 psi / 20psi
#125806, "RE: Ignition short" In response to Reply # 7
I rewired my entire system from the battery years ago with gold terminals. no more corrosion.
the nice thick 4ga wire helps too
Erik P. Official 2GNT thread Hijacker Some say that he's driven over more Covenant than he's shot, and that his grenades aren't where you'd expect them to be... All we know is, He's not The Stig... But he is The Stig's Spartan cousin!
#125809, "RE: Ignition short" In response to Reply # 8
Good stuff here. Glad you got the problem fixed man. I still have that craptacular ring clamp on mine but I think I'll switch it out and see if I notice any small improvements.
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