http://go.mrgasket.com/pdf/300+DFI.pdf

This is their idea of a wiring diagram......jeeze

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Sam, can I ask why you dumped MegaSquirt?

Ignore me, I found your answer elsewere (the I'm back post).

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'15 Chrysler 200S V6
'74 Duster 360, factory 4 speed car

I chose to "upgrade" to Accel for several reasons: The most important was the lack of timing control. I did not have MSII installed, although that was isort of in the works, and the turbo demands timing control. Another reason is features Accel has that MS does not have. The maps in Accel are 16x16 which is twice the resolution of Mega Squirt, and 50% greater than MSII. The tuning soft ware is amazing. Once we solve this problem, tuning should be easier, and more flexible than MS. Accel has idle air control which MS does not. Even MSII, which is supposed to have IAC, apparently did not work that well, according to the posts that I read about the IAC problems on the MS forum.

In retrospect, it looks like SDS would have been better. But, who knows. As I have said before, I am where I am now, and must just work through this. In retrospect, it might have been better to go for the MSII first, but it seemed at the time that the Accel thing would actually get me where I wanted to go faster. I just didn't know I would be having this problem I am having now.
Sam

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I apologize for even bring it up (in the midst of your struggles). I was curious as I have just disembarked down the MS highway (good deal I couldn't pass up), but I should have lurked around and found the answer without poking at your open wound.

I have nothing against any of the other aftermarket EFI setups, only that I can't afford them. Truth be told, you usually get what you pay for, so in the end you should be really happy with things. I'm sure you will be back in the saddle soon.

Sure would like to see some picture of your setup (hint, hint).

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'15 Chrysler 200S V6
'74 Duster 360, factory 4 speed car

I hope you are right Dion. Sandy I am with you, I went on the we site I indicated, and couldn't find what I thought I was going to see. When I was at Total performance, there was a site that had tons of diagrams, of all kinds. He must have copied it down wrong. I will find out next week the correct one, and go from there.

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I had all sorts of trouble with electrical noise on my Megasquirt. One of the things I did to get that to go away (besides moving the ground from the alternator housing to the engine block) was to put an audio noise filter on the wire giving power to the 'Squirt. Now I've got all the noise issues solved except that the power sometimes gets interrupted when I turn the key from Run to Start.

To answer your questions:

1. Low impedance injectors can burn out the injector driver circuit by drawing too much current. Check them with an ohmmeter.

2. Heh - I accidentally did the same thing to mine, wired it up backwards. This normally won't break anything, though.

3. Grounding it to the battery should be safe.

4. Non-resistor plugs can cause a good bit of interference. If you have any of the input wires coiled around a spark plug wire, I could see that giving you a voltage spike.

The two things most likely to burn out an ECU, I'd say, would be too much injector current and accidentally taking the ignition signal from something with too much voltage. Megasquirt uses optoisolators to make it physically impossible for current from the ignition system to get into anything besides the ignition input circuit; I'd assume the Accel box is set up the same way. If you are able to get the Accel box open and find just which circuit burned out, that would be a useful clue.

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

Now thats a bit scary... Smells like bad design or bad string of parts.

Matt brings up a good point about the resistor plugs too.

Did this one fail in the same exact manner as the first go around? I think last time you said the ecu wasn't recognizing any pulses from the distributor - this input circuit is independent of the injector output circuit so even if you had the wrong injectors it probably wouldn't matter in that regard, but still something important that would need to be taken care of. If you have low impedance but accel ecu needs high impedance you can add inline resistors, preferably of the non inductive variety. Easy to grab from JY cars.

If tps is just reading backwards, it won't fry anything. As long as its reading, your fine.

Ground loops can cause nasty things to happen. My main ground to MS harness comes direct from battery, but all the sensor grounds are tied together at the MS board.

About the plug wires leaking spark - it is one possibility but its a stretch - thats why I had suggested shielding the distributor pickup wires in that area.

Can you run the ecu in fuel only mode? Have the distributor trigger Accel/MSD box direct, then run the tach output from msd box back to trigger ecu?

Pierre, I see your point about Fuel only operation. You suggested this before. I don't know if that could be done, but it probably could be a work-around thing so to speak. It is possible to force the timing at a set number in the tuning screen. This would have the effect you are looking for. It seems like that would only put off the inevitable of having to find the source of this failure.

The ECM did fail in the same way, and after the same period of time. For the record, I wrote to Rance that the ECM died again, and asked if he had any useful ideas, and he never replied. Either he did not get the message, or is just too busy now that he has my money. Either one is completely unacceptable as far as I am concerned. If I ran my business the way he runs his, I would be out of business by now. Warn any potential customers about the frustrations they can expect when dealing with him. He has a pretty web site, but his support and service do not match up.
It bothers me to say negative things, that could harm another, but I feel the need to save others from the hassle I have gone through here.
Sam

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The failure was a transistor in the section of the ECM that handled the ignition input, wasn't it? The Mopar distributor pickup can put out somewhere around 50 volts. If you had it hooked up to the wrong circuit, I suppose it could work as a trigger but feed too many volts into a section that wasn't meant to handle that. Check the ignition input wiring and be sure you have it connected right.

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

Matt, are you sure about that 50 volts thing, or did you mean 5.0 or even .50? Fifty volts sounds very high to me. The UIP feeds are sending their signal to the top two, most exteme right pins on the ECM, and this is what is called for. Just to be sure, I have ordered the correct UIP harness to replace the jury rigged dual sync set up. It could be that this is a source of problems here. There is a twelve volt lead in the dual sync harness, and perhaps this is shorting across to the IUP leads and sending a surge back to the ECM.

If you are right about the 50 volts thing, then that would be a serious problem. Maybe a voltage regulator is needed in the circuit. But then you would think Accel would already have that in there. By the way, thanks for the further input. I don;t feel so alone in dealing with this now, as Total Performance is on board, but your willingness to contribute, and your input, serves to keep me in the hobby now, since my car is somewhere else, and I am no longer working on it myself. It's like a family member has gone off to join the army in a foreign conflict.
Sam

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Yes, that's not a typo - the VR sensor in the stock distributor is basically an AC dynamo, and its voltage increases with RPM. Neither of the wires in this system are safe to ground to anything else. I believe the Accel documentations call it an Inductive Pickup or IPU. Unfortunately, Accel's website does not give much about pinouts, so I can't confirm if that is the correct way to wire it up or not.

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

I'm surprised that you have not looked at megasquirt-Extra. Using Megasquirt-I.

This supports ingition curves (dual), and fuel control. Many used this for turbo also. This is best done with VR sensor on the toothed wheel mounted to crank for ingition accuracy.

Also can be adjusted while running via notebook computer.

Cheers, Wizard

I'm not going back to Meg Squirt just yet. Thanks for the clarification Matt. I will ask Fred if he thinks 50 volts could hurt something in there. If it were hooked up wrong, you might think it could. I haven't looked it up, but I thought UIP was for Universal Inductance Pickup. Maybe I have that backwards.
Sam

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