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Old 12-10-2019, 04:25 AM   #1
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Default Bench-diagnose my aftermarket-ECU'd redblock problem ...


So I was out earlyish this morning taking the 242 to a mechanic, to do something I could probably do myself but am too lazy, when karma struck me down for said laziness. Stalled & wouldn't start on a really busy road just prior to peak.

It's a B23/0/E+T, MoTeC ECU, home-made loom, all sensors & actuators were new (10-15 years ago), and in particular 4x (5yo) OEM LS1 ignition modules.
I managed to roll downhill & around the corner to get out of the heavy traffic, and started playing with the (still stock) interior fuse-box before remembering that all the ECU stuff had been done via relays & fuses under the hood near the battery.
Poke here, jiggle there, wouldn't start - seemed to nearly catch on occasion but wouldn't keep running. Note that it's got a really grumpy idle once warm, and it'd only just gotten out of it's cold-start cycle.

So just before calling the motorists' association freebie tow-truck, I pushed the four plug leads harder onto both the plugs & the coils ... and she fired right up.

In people's experience with coil-per-plug setups that aren't directly coil-on-spark, what are the chances of a lead having come loose? The ignition modules are atop the cam-cover on a bracket, so the leads are only around 1/2' long. Is one of the ignition modules possibly a dud & me poking it temporarily re-connected something intenally ... is it likely I've got a dud lead which re-connected as a result of my poking?
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Old 12-10-2019, 02:54 PM   #2
Dirty Rick
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I think fiddling with the plug wires and it starting was a coincidence.

I'd connect to the Motec and do a sanity check maybe a log and see what is happening if you can make it repeat. Intermittent problems are the most difficult to diagnose. If it is not running smooth I'd start with spark plugs. If the plugs are nasty it may need some tuning where it does not spoil plugs. Make sure it doesn't have cold plugs in it, Id use the factory plug for the application and monitor for problems at high load after getting the other areas sorted out. Being that you have COP the chances of all 4 coils going bad at once are slim, unless it is a power or ground issue that is common to all 4 coils. Check timing with a light. Does a Motec have a sync loss monitor? Check fuel pressure static, idling, and under load. Fuel pump relay, main power relay? Did you hear the fuel pump running when it wouldn't start?

Just because it says Motec on the ECU doesn't make it any different to diagnose. Your first clue is it is "it's got a really grumpy idle once warm". Not sure about Motec tuning strategy works, but a MS relies on the hot idle tune as a base for cold start and idle trims.

Which tuning software are you using?
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Old 12-11-2019, 11:04 PM   #3
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In my experience, if one of the coils is dead the car will still start. It’ll run like **** but it will still start. The above suggestion about plugs may be something to look into but I would look at the fuel side first. It just seems random that you’d lose all four coils at the same time. It’s possible but I’d look for something simpler first.

With ms, I could go into turner studio and manually command the fuel pump to come on. Can you do that in your tuning software? Next time it doesn’t start you could try this and see if you hear the pump running. Then there’s always the old starter fluid into the intake trick but let’s use the technology we have.

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Old 12-22-2019, 01:16 PM   #4
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Did you ever get this fixed?
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Old 12-23-2019, 02:40 PM   #5
Stiggy Pop
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Originally Posted by Dirty Rick View Post
I think fiddling with the plug wires and it starting was a coincidence.
I thought the same thing earlier this year when I lost a cylinder headed home from work. Did all sorts of diagnostics including ohm'ing the plug wires which tested good. Well, turns out the wire had failed but if you happened to have it in the right spot it'd work, wiggle it again and it wouldn't. Pulled the plug wire out of it's protective bootie and it came out in two pieces.

Where do your wires sit relative to your hot turbo stuff? I would be considering a failed wire due to heat.
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