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Microtech microtech ltx12 suddenly no spark

Old 08-20-09, 09:58 PM
  #1  
kel
24 yrs driving 2nd Gen RX
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microtech ltx12 suddenly no spark

Hi Gang,
I have an '88 TII with Microtech LTX12s that I just drove home to Denver from Montana. No probs at all on the way home or the first week driving to work.

On Monday, returning to my office after lunch, the car died as I gently bounced into the driveway. Noticing that the lights were out on the ECU, I checked and found a blown fuse. Replaced the fuse, started right up and drove to my parking spot.

After work, the car started right up, but about a half-mile down the road, the idle dropped to 500 or less. Turning a corner with the clutch in, it died and wouldn't restart.

Got it towed home today and started looking into it. Found that there is no spark. I'm going to look through the wiring for anything obvious right now, but would appreciate input on how to troubleshoot this.

The ECU has lights and the amber one flickers while the engine is cranking. I have a spare spark plug on a spare wire hooked up so I can see activity, and there is none. Also, there are no further blown fuses in the driver side block.

Thanks,000,000 for your help!

- k -
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Old 08-20-09, 10:16 PM
  #2  
kel
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Update:
Found that the after-market igniters have their own pair of fuses and one of them was blown. I replaced it but still no spark. Found that now the ECU feed blows immediately when I turn the key to the ON position.

Thoughts?

- k -

Post update update: found that the blown fuse doesn't directly feed the ECU, though the ECU lights are dark when it's blown. Where it does go is to a fuse block under one of the after-market igniters - Bosch HEC715. This block has a 30amp fuse I referenced in the beginning of this post. So, from the inside fuse block, there is a 30amp which feeds this 30amp fuse, which feeds all four igniters on the + terminal.
I'm tracing wires to see where all this stuff goes, but it seems to me that it would make more sense for this fuse block to get it's power directly from the battery cable since it's less that 18 inches away instead of going through the firewall to the interior fuses. Would anyone agree?
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Old 08-20-09, 11:06 PM
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kel
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Post post-update update:
Okay, here's the final scoop. Ya can't wire it like i was just thinkin' 'cause the ignition is always on and when you turn the key off, everything shuts off except for the engine.

Anyway, what was blowing fuses, is that the negative battery cable was run so close to one of the igniters, that the spade connector had worn through the insulation and caused a direct short to ground on the + feed to the coils. Soon as I corrected that, the resistance readings looked better and the fuse didn't blow.
I replaced all the connections, hit the key and it starts up just like new again.

Thanks for all your good thoughts. I'll post pictures on my site soon so's y'all can see what i'm talkin about

- k -
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