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RFI causing shutdown?

Old 07-05-15, 07:03 PM
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RFI causing shutdown?

So the car shut down on the highway with no warning, all i know is that there was no power to the fuel pumps for lack of noise and pressure gauge at zero, and no lights on ecu. (mtx8) the ecu was cold tothe touch.
Few minutes later checking for loose terminals or blown fuses (all was good) she was powering up again.
Drive off, make it as far as next fuel station, dead again.
Call up a free tow, get a coffee, check again, the car works again. I took the tow truck anyway after not being able to talk him into following me the 8km home.

Long story short, is this a thing? And what should i check? As its an intermittant fault and it currently works, i dont feel like stranding myself half way across town before i can start trying to diagnose.

Any suggestions?
Could the CAS wire or loom in general be picking up white noise or something?
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Old 07-11-15, 10:16 AM
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Check for loose grounds.

Check the Microtech connectors.

It sounds like it is a heat issue. Could be a relay dropping out due to heat, etc.

You're going to have to bring a meter with you and when it happens again, start measuring.
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Old 07-11-15, 05:56 PM
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Thanks Aaron, will do. Now im thinking it was the fuel pump relay, (i neglected to mention a fuel pump upgrade) but the green light on the ecu doesnt seem to work anymore which was cause for some of the confusion.

If i can get my **** in gear will be rewiring the fuel pumps today, and definitely be bringing the clamp metre with me next time.
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Old 07-28-15, 03:35 AM
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Ok, i should probably start a new thread for this but i believe it is the same problem as i mentioned above, in that it might be something else completely - possibly actual gremlins.

So when the thing stopped getting fuel, and then later started again, one thing of note was that the ecu (mtx8) had NO green light when it was running again. The yellow light was blipping away happily. I figured maybe it was just the led

Anyway, apart from that it seemed the fuel pump relay might be overheating, although i didnt notice at tje time, have since replaced the microtech-spec 30a relay and pissy wiring running both lift and efi pumps with a 60a relay and heavier wiring

Only just got to check it today (fuel injectors took 3 weeks to get back to me) the pumps worked with ignition for 10 seconds like they were supposed to when i checked for fuel leaks.
By the time i get the UIM back on and buttoned up again guess what - no power to fuel pumps.

After much checking things it seems that the pink wire for the fuel relay which is supposed to be +ign-on is now constant earth, and the green wire which is supposed to be switched earth from ecu is now hot (as in constant +) so that if i plug the relay back in the pumps come on whether the key is in the ignition or not.
Which it decided to start doing sometime while i wasnt watching, apparently of its own accord.
Also i could not find ANY power at the ecu at the pink (ign) OR red (batt) terminals.
To reiterate, the ecu was running ok with no green light on before this.

Hopefully any of this makes sense or sounds familiar to anyone. Or am i going mad?

Last edited by WANKfactor; 07-28-15 at 03:39 AM.
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Old 07-29-15, 12:20 PM
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you found your own problem.

Trace both wires. Make sure PINK is not shorted to chassis and goes straight to IGN 12V power. Make sure GREEN wire touches nothing until it reaches the ECU. Check relay socket and make sure things are not in contact. Electrical is pretty straight forward if you take your time. Don't leave a single centimeter unchecked. Worst case, cut both ends of the wire and make new pink and green wires and terminate them correctly. Like you said, PINK should only turn on when IGN is on. Green touches absolutely nothing but ECU and relay socket.
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Old 07-29-15, 07:53 PM
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^ thanks mate. So i went back into the garage this morning to do what you suggested. Pulled the uim off so as to have full access to the loom, reconected the neg on the battery and started tracing wires. Everything seems in order except this time im getting nothing at the pink(ign on) and green (ecu earth) fuel pump relay.

Found the "engine" fuse blown, replaced it, now everything works, including ecu lights (green solid, red flashing) but the engine lights on the dash are not coming on, which is yet another new development.
Sit manifold back on so i can attach sensors, turn ignition on - everything seems to work - ecu showing green and yellow solid as it should, but no engine lights on the dash again.

What should be my next step? Im almost tempted to button the manifold down again and just try and start the car.
I was thinking the ecu was on the fritz but now not so sure. Im replacing it shortly with an LT10 but need to make sure the car works first.
It keeps doing wierd **** when i havnt even changed anything.

Please excuse my ignorance, wiring and me are not great friends, lol, so any help is massively appreciated.
The car is an '85 fb. Aus spec, so originally non- efi.

Last edited by WANKfactor; 07-29-15 at 07:57 PM.
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Old 07-30-15, 11:39 AM
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I would find out why "engine" fuse is blown. Check wire from the engine fuse to the ECU. Make sure some yahoo didn't connect bunch of devices to it drawing too much amp. Make sure there is no short.
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Old 07-30-15, 11:57 AM
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what capacity is your IGN fuse and relay? what did you add to it to convert into the EFI? It's best to dedicate all your add-on to IGN relay #2 with signal wire coming from the OEM IGN relay. That's what I have done.
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Old 07-30-15, 03:55 PM
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Thanks for the leads man. I'll see if i can print up some wiring diagrams to identify thos relays and fuses and see what these cowboys have done.
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Old 08-01-15, 10:20 AM
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Fuses don't blow without a reason. Something is up here.

Is the Microtech harness in any way tied to the stock harness?

If it is, then it should be isolated completely.

Wiring diagrams of how things were done would be helpful.
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Old 08-02-15, 03:56 PM
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Thanks Aaron, i was hoping you'd reply. I downloaded the factory wiring pages from foxedca the other day, but found it a bit overwhelming. Will have another crack at it today.
Ill draw up a diagram of how thr ecu is rigged too.

Last edited by WANKfactor; 08-02-15 at 03:58 PM.
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Old 08-24-15, 02:08 AM
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In the name of etiquette i better report back. Issue turned out to be a dicky fuse. Its embarrassing but it started playing up after a tune and a fuel pump upgrade along with other things so was chasing my tail looking for other problems.
Moral of the story, check every fuse with a test light . Just because its not blown doesnt mean its good.
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Old 08-29-15, 10:39 AM
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Wow. Million to one shot. Glad you got it sorted out.
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Old 08-29-15, 06:05 PM
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Thanks Aaron, but you're too kind. I'm sure someone more experienced would have had it sussed in 15 minutes.
I had it going the minute i got home after talking to an auto elec who told me to check all the fuses in situ with a test light.
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