Today and yesterday I undertook the task of cleaning up the wiring under the hood. In the process I did something that now makes it run rich. I moved 4 fuseblocks, and the Mega Squirt relay box. So far I have not changed any of the sensor connections. The wires are too long now, but I was going to test it first to see if it started and ran before changing those. Any ideas about what I could have done here? It seems the intake air temp and the coolant air temp might be the culprits. Could I have damaged the sensors by maybe putting a voltage across them I should not have? I don't think I did that, I am just throwing out ideas. All ideas are welcome. The good news is it starts and runs, so it should not be too difficult to figure this out.

The only thing I know for sure is not done yet is the coil is not bolted back down, so has no ground. It does not seem like this should make it run rich. Thanks for any thoughts.


I am off to the movies with my wife, and will take this back up tomorrow after I have thought about it and read any posts here. Thanks again.

Sam

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See if you may have unplugged the MAP sensor hose...

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It's a Slant thing. Even I don't understand.

1974 Duster, EFI /6 soon to be turbo...

Get that Monkay! Get that nasty thing!!

Good thought! Although I think I remember the MAP reading on the laptop being a normal 40 KPA. But thanks. I will check it for sure.

Did I mention that the coil is currently ungrounded? I cannot see why that would effect fueling. But this stuff surprised me often. As you can tell from the time stamp, I am up in the middle of the night thinking about this. I just wrote a long letter to Peter asking for his advice.

Sam

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Coil should not need to be grounded. HEI brain unit - yes. Unplugged clt temp sensor?

Lou

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Home of Slant6-powered fun machines since 1988

OK, So here is where my stupidity, and willingness to go public with it will save one of you guys heartache down the road. I broke the cardinal rule when I first started working on the project. I left the battery hooked up for about one minute too long. In the initial investigation about how I could arrange things on the fender, I unhooked the ground wire from the HEI to the relay box ground contact, to see if I could turn the box 90 degrees and have it take up less room on the fender. This was in an attempt to make enough room on the fender to get the MSD box back in the ignition. The ground wire sprang from my fingers, and its curl sprang it over to exactly where the bare alternator feed nut is on the back of the alternator. .AARGG! It was oh so short. Maybe just a few ms. I proceeded with optimism, but a momentary spark can do lots of damage. When I posted yesterday, the momentary spark had slipped my mind.

The first and most obvious casualty was the fuse protecting the alternator's feedback voltage wire. But for it to get that far, the spike had to travel through the ECU and out the ECU power feed to the fuse block. The fuse block is otherwise isolated from the batt+ until the key is turned on, and the key was off when this happened. AT that moment the only path to the fuse was through the ECU.

I wrote to Peter after getting back home last night, giving him all the details. He said to check for voltage on the two injector wires when there was NO rpm count, but the key is turned on. Presence of voltage there with no RPM count would indicate damage to that circuit, allowing more fuel to flow than the fueling command at any given moment. This check showed there is indeed 12 volts going to both injector banks with no RPM counts. So, back to Peter the ECU goes.

It is amazing how resistant we are to learning. This habit of thinking we can get away with breaking the rules, (in this case rule number ONE), is part arrogance, part optimism, part laziness, and part lack of previous painful experience.

So there you are. Smart folks learn from others' mistakes. Are you smarter than me? Then do not do any wiring on your car with the battery hooked up. If you even think, "Yeah but.....", you are just as dumb as I was.

Edit, just ten minutes later: I just heard back from Peter. He says maybe my results are not so bad. The bad news would be a short to ground in the injector circuit. This would indicate something burned out. I will let you know how things work out.

Still, unhook the battery before doing electrical work on your car. You never know where that wire is going to flip to when it slips from your hand.

Onward and Upward.
Sam

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I just sent a data log to Peter. I will keep you posted on his reply. Would anyone else like a copy sent to their e-mail?.... PM me. It was very hard to start, and clearly flooded. I felt lucky to get it started. The battery charger is in order.

If this were a fresh start up of a newly installed MS system, I would simply reduce the prime pulse and the req-fuel, and think things were fine. But the fact that it ran so well before leads me to believe I have screwed up something here. Everything looks good. The MAPreading was actually 32, not 40 as I remembered. The pulse width was 1.7, which is normal. Temp readings looked correct. RPM agreed with the dash tach. Timing was correct.

Sam

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You might want to try reloading the firmware and reloading the MSQ file from before this happened; could save trying to repair the MS.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

Thanks Matt. That is hopeful. Peter now thinks maybe this is an ignition problem since the datalog all looked good. Maybe the richness is simply unburned fuel from very poor spark. When I try to start it, it fires immediately, then goes out and is flooded from there.

Maybe either the HEI module has been compromised, or the lack of a ground on the coil could be making it all work poorly. I will ground the coil first, then try it again. If that is not good, then maybe try a new HEI module. They are pretty cheap. If that does not work, then I will bug you about leading me in the effort to reload the firmware. I am out on the skinny branches there. My daughter did it the first time. I do have a good file to reload after that, and I think I know how to do reload an old tuning file.

Let me run this by you. If I open the old file first, and then connect to the ECU it will ask me if I want to use the settings in the ECU or those in the laptop. If I click on select laptop, then at that point all the values and settings from the earlier tuning file should be installed. Yes?

Here is the bottom line: do the recorded pulse widths represent what is actually happening? If so the rich readings are not the ECU's fault, but the ignition systems fault. But, how can I tell if the 1.7 ms pulse width is true, or if the injectors are doing something on their own outside the guidelines the ECU instructing and are being recorded in datalogs? Is this even possible? Peter says there is a slight chance the flyback system has been damaged, but thought that was unlikely based on the MAP readings he was seeing. That went over my head.

Sam

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Yes, that will reload the tune.
They'd better.
It is possible - if you have an oscilloscope. You'd put the scope on the injector output and check the length of the part where the injector pulse goes low.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

This post is going to read A LOT like Lou's solution back when he thought he had a couple of broken rings in number 5 and 6. The slant now starts up with a bang,and seems fine.

The culprit was ................TA-DA!................ The distributor cap. That's right. It would not start at all this morning, so, assuming something expensive, I went and bought a new ignition module from NAPA. Didn't fix it. Folks had been trying to get me to try another module anyway, so no biggie.

When I went to pull the center wire on the cap to check for spark, I could not quite believe what I was seeing. There was no center wire. And the center post had melted and turned black like charcoal. With a little searching I found the center spark lead totally away from the cap. I had apparently pulled it loose while fiddling with the coil, but at the time it still looked like it was in place. Apparently it had benn close enough to arch over to the center post and burn it up. The boot was burned through on the side. Eventually the leadt worked its way far enough away from the center post that it would not run at all.

A new NAPA M-40 cap (tan with copper contacts) and a new wire boot later, and it started with a bang. It still looks a tad rich, but it is very cold out, and I usually drive away, so do not see idle AF ratio when cold. It smelled correct. Within a minute or so it was up to 12.5:1, and the ECT was just 45. So, I shut it down and will do just a tad more house-cleaning with the wiring tomorrow.

So what did I learn here?

1. Always unhook the battery when doing wiring. True, this problem was not related to the stray spark that alarmed me, but it could have caused damage,and at the very least I wasted time and energy chasing a real red herring.

2. Start trouble shooting with the cheapest and most basic components first. I should have checked the seating of the spark plug wires first, not 2 or three days later. Basic and simple. Right, Lou?

I will post a photo of the cap later. I did not know bake-lite would melt.


Sam

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It will be interesting to see how it behaves under boost. Maybe this fixed your VR noise issue?

Scott

My thoughts exactly.

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It's a Slant thing. Even I don't understand.

1974 Duster, EFI /6 soon to be turbo...

Get that Monkay! Get that nasty thing!!

Very cool. Right on...

Lou

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Home of Slant6-powered fun machines since 1988

I hope you are right, but I am not betting the farm on it. The wire was seated correctly before I fiddled with the coil and yanked on it. And the cap that burned up was only about 3 weeks old. I knew exactly which part number to ask for.

Here is the burned cap. That is NOT rubber from the boot on there. That is melted bakelite, or whatever they are made of these days.





Sam

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Uh…wow! It takes quite a bit of heat to turn glass-filled alkyd into charcoal like that.

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Too many people who were born on third base actually believe they've hit a triple.