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Old 07-26-2017, 02:54 PM   #1
Captain Obvious
I lack discipline.
 
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Join Date: Nov 2005
Location: U.S.A.
Posts: 184
Exclamation Need Help with ECU Ground(s)

I've been trying to resolve a spark blowout issue with my rebuilt 2003 Mach1 for longer than I care to admit. Every time I start my car, the dash lights all come on as all of my gauges do a full sweep for 3 to 4 seconds before functioning normally. Given this telltale symptom and my tuner's conclusion that spark blowout is occurring based on my data logs, I'm convinced that my ECU has a very poor ground connection or the ECU itself is damaged.

On a few side notes, I have a brand new Motorcraft battery and can see that my average voltage while driving around is about 13.5. My TR6 plugs are gapped at a tight 0.025", since I'm running a TVS blower with a 2.8" pulley (and stock lower), along with a 9.5:1 CR and stage 3 heads/cams. I've experimented with TR7 iridium plugs and larger gaps along the way, all to no avail. Fuel pressure issues have been ruled out.

While my contributions to this forum are severely lacking, I'd deeply appreciate some definitive answers (or corrections) to a few simple questions:

1. Where does the power supplied to the coil packs ground at? I'm assuming since the coil packs are powered by the coil drivers inside the ECU, the answer is ECU ground.

2. There is a small, short chassis ground wire right next to the ECU box itself. Does this solely constitute ECU ground, if at all? I'm guessing the answer is no.

3. There are two small black ground wires coming out of a pigtail under/near the fuse box, both of which follow along the battery ground cable and ground at the battery. One of these black ground wires also grounds to the chassis along the way. Is this the ECU ground wire I should be concerned with? Or the other? Or both?

Regarding the pigtail referenced in my 3rd question, I did recently find a non-trivial amount of goop and dirt inside which would absolutely compromise conductivity. I'm not sure what got in there, or how. I've yet to get things back together for another test drive after spraying this pigtail to death with electronics cleaner. I do have a replacement ECU on-hand but am still debating whether to throw it in before I hit the road again. Part of me wants to see if this dirty pigtail connection has been the problem all along.

Again, any information or advice offered here will be hugely appreciated.

Here's a picture of my engine, which is probably making less than 100 HP at this point:



__________________
2003 TVS 298ci Mach1
< 100 RWHP

Last edited by Captain Obvious; 07-27-2017 at 12:00 PM.
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