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Old 01-31-2018, 04:29 AM   #1
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Exclamation serious mess up of the ECCS on a z24, big failure, seeking perspective

here's what happened, stupid idiot thing to do. wanted to read diagnostics on the ECCS/ECU/EGI beneath the passenger seat, this is a 1986.5 z24, sweet, thought i had to do the screw one way then the other, come to find out i was just unscrewing a screw that's part of the computer, because this is the older ECU which you just run diagnostics through by pumping the clutch, ect.

so the ECU lights up like operation, at the screw contact, sparks, the fuel pump goes on and off, like it should, because the ECU is turning on and off, then the ECU suddenly has no power. probably short circuited or something...

i go look at the relays, realize there's a green one in a blue port and a blue one in a green port, i switch em, see if the ECU comes on, no, still dead.

then i open it up, get the voltmeter, register that the 12vs is coming through to the computer, so it's definitely the computer, then i poke the voltmeter around looking for the power break and i find that when i put the ground point on the three pronged rods that go into the board, that were directly impacted by my unscrewing the wrong screw, eureka, the ECU powers on, fuel pump engages, but then there's weird clicking in the relays, i decide to try and start the truck.

truck goes, no, like it electricuted itself. no there's no power, it's got power when i hook it up to a battery charger.

now, any perspective on how badly i've messed up? i put the relays back to their original positions, that didn't do anything...

thanks for yr future perspective, it's really helpful to be able to ask for help.

Last edited by nothingtoseehere; 02-11-2018 at 05:07 AM.
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Old 01-31-2018, 03:13 PM   #2
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get a boneyard ECU
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Old 01-31-2018, 06:43 PM   #3
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Quote:
Originally Posted by street_rulerr View Post
get a boneyard ECU


yeah, that's my first order of business, gona do that today or tomorrow.

any chance you know the proper relays for the four relays in the engine compartment? i want to make sure those are proper, i forget which was in which, there's two green ones and two blue ones, i can take pictures if that helps, i'm not looking at the truck right now, but they both have four numbers on them, two numbers connected by some kind of symbol that seems to signify the circuitry.
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Old 01-31-2018, 07:35 PM   #4
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do you have a big double plug relay on the right side, behind the batt?
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Old 01-31-2018, 07:39 PM   #5
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i dont unfortunately. I have a 96 so im nor sure what i have would translate. however if you are able to get a boneyard ECU, look at the relays while you are there.
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Old 01-31-2018, 10:59 PM   #6
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figured out the relay bit. this is just for anyone who might want to know. 25230 c9965 12v the green one is used for fuel pump relay and p.t.c relay while the blue one 25240 c9970 is used for the main relay and the check relay.
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Old 01-31-2018, 11:34 PM   #7
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i am also wondering if there is a way to check to see if the relay fuses are actually working. when i crank the truck it just does an electrical click, before it would crank but not start because there was no fuel pump.
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Old 02-01-2018, 10:40 AM   #8
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The schematic for the relay should be printed on them. If you are good with a voltmeter, I'm guessing you can read that.

You can unplug the relay and create a short piece of wire with a spade connector on either end that completes the circuit that the relay normally only activates at given times.

If the truck cranks up with the relay bypassed, you can go to the auto parts store to get a new relay. The terminals can get corroded on the old ones, and they are cheap enough to replace.

Though not a complete source of info for your truck, you can follow the link in my signature to grab the 1989 Service Manual. In particular, the code reading section is different, but I think the location of the relays and the wiring of the Z24 is the same.
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Old 02-02-2018, 10:45 AM   #9
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Quote:
Originally Posted by nothingtoseehere View Post
yeah, that's my first order of business, gona do that today or tomorrow.

any chance you know the proper relays for the four relays in the engine compartment? i want to make sure those are proper, i forget which was in which, there's two green ones and two blue ones, i can take pictures if that helps, i'm not looking at the truck right now, but they both have four numbers on them, two numbers connected by some kind of symbol that seems to signify the circuitry.
Download the Factory Service Manual for your rig on this website. The one for mine runs over a thousand pages. You will never buy another Chilton's manual. The FSM is God. It covers virtually EVERYTHING.

You may have fried a circuit in your computer. No use trying to fix it. Get another one. Search Craigslist for ones being parted, visit wrecking yards, or go crazy at eBay. Pretty much the only way these days. Or try to buy one here onsite from a member.
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Old 02-03-2018, 06:54 AM   #10
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about the fusible link, after the jumble of plugs that is right off the positive battery terminal, just down the line a bit, there's a rubber housing that seems like it could hold a fuse, it has two metal slots in it, but there's nothing plugged in there, is that a place where there's supposed to be an actual fuse?
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