Car shuts off randomly- Electrical gremlin. ECU??

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S14wayz
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Car shuts off randomly- Electrical gremlin. ECU??

Post by S14wayz »

Hey there,

Been working on a buddies 89 Hatch with an RB25DET S1. Everything was good then had consistent and weird electrical issues. Fuel pump relay is jumped by the last owner for whatever reason. Big thing is the wiring is a mess in this car and by accident i pulled 12volts off the ecu and jumped it to a wire thinking it was the tach signal wire. I was reading the pin out upside down and the guy used the same colored wire for this pin so I screwed that up and assume I potentially could have fried something in the ecu. All this happened after jumping 12V to incorrect tach signal wire. So that's why I feel like this is ECU based now. On top of that the symptoms are just wacky that I feel it could be computer based.

Symptoms:

1. First fuel pump stopped working completely. Didn't turn on with IGN on. Pulled pump and tested it and it works. Checked for 12V to fuel pump and it was there. We were planning to hard wire it anyways so I kinda stopped diagnosing it there and thought its probably a grounding issue somewhere.

2. After hard wiring fuel pump the car ran for a bit and thought it was fixed then the gauges stopped working. Thought that was just a power wiring issue. Then they turned on again randomly and was good for a couple mins then flashed off and car died at the same time.

3. Now car as it sits you sometimes can fire it up it'll run smoothly for about a minute then cutout completely. The other day it ran for about 5 seconds then shut off. (I thought maybe some heat related thing for a sensor but if it shuts off after 5 seconds that kinda rules that out)


-Checked all engine grounds there good
-Checked all fuses there all good
-There's current draw on the accessory fuse with car off (cant remember how much), I looked at wiring diagram and checked relays. That circuit is hooked up to Accessory relay #1 and accessory relay #2. Idk where the hell acc relay #1 is but I pulled ACC Relay #2 and the plastic where the prongs sit is a tiny bit brown/burnt...It also felt warm when you crank over the engine and let it run for a min before it shuts off. (Idk if thats a normal symptom of an accessory relay?)


I have trouble with electrical issues especially ones of this nature there's so much **** that can go wrong. Im pretty overwhelmed by it so could use some insight

Thanks guys and gals
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S14wayz
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Re: Car shuts off randomly- Electrical gremlin. ECU??

Post by S14wayz »

Here is some additional stuff

Video of shutoff

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Fuel relay jumped this way

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Showcasing how **** it looks

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S14wayz
Knows Some Stuff About 240's!
Posts: 419
Joined: Wed Apr 24, 2013 11:11 am
Location: BC, Canada

Re: Car shuts off randomly- Electrical gremlin. ECU??

Post by S14wayz »

Finally figured it out turned out to be the connector to the crank angle sensor. Looked fine but just re pinned it and it seems good.
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