After three weeks wait, and an accrued cost of $750, the car ran for 20 minutes once again, and then failed once again. Total Performance is pulling their hair out and now must dig into the wiring harness to find a possible source of some harmful feedback to the ECM through the sensor wiring, or perhaps the MSD box in some way.

I did modify the wiring harness heavily, but was extemely careful to keep wires correctly matched to their proper colors, and heat shrink tubed everything.

Any ideas? Some early thoughts:

1. Could the injectors be doing this? I got them from Rance along with the other stuff, so it seems like they should be appropriate. They ran for several years with the Mega Squirt. How do I identify high Impedence injectors from low impedence, and how does the wrong one cause damage. Lou, I know you burned out something on your Mega Squirt system early on with a mismatched injector impedence. Can you elaborate on that.

2. The TPS sensor was reading backwards in spite of the fact that the wire colors were correctly hooked up. I had to reverse two wires to get it to read correctly. Could this, or would this indicate something miswired within the harness? AFter switching the wires the TPS switch responded normally.

3. Could there be a ground missing somewhere? Could lack of a ground allow current to flow in unwanted paths?

4. Could spark plug wire leakage jump over to the pickup for the distributor, thus burning something out? I have not seen the car since Total Performance put things back together, so I do not know what their wiring looked like.

I am driving up there first thing tomorrow to take a look myself, and see what I can see. Any thoughts to share with Total Performance before then would be appreciated. Right now this car is getting to be a smaller and smaller part of my life. I haven't seen it in almost a month, and have done nothing to it myself, which is one of the main joys of owning it in the past.

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Oy.
Get Accel to take back their stuff and go get an SDS! Seriously, let's see if we can figure this out. What is the nature of your charging system? Which type of alternator are you running, where did you get your specific alternator that's on the car, and what exact regulator are you using?
Depends on what part(s) of the ECM failed. If it's the injector drive circuitry that keeps frying, then perhaps the injectors are either incompatible with this ECM, or are faulty and drawing too much current.
You call Accel (preferably from a phone that doesn't belong to you), say you are considering their system, and ask what the acceptable injector impedance range is for their system. Then you put an ohmmeter across each of your (disconnected) injectors and see if they match up.
Excessive current through the ECM's injector driver circuitry
Potentially.
Yes and yes
Anything's possible, but this scenario is highly unlikely.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

revise the location of the ECM. Not anywere near the coil (s) or big electronic/electric devices such as alternator, distributor, starter, starter's relay, the big firewall connector, or stuff like that. Sometimes harmful magnetic fields interference may occur. Most likely your ECM is located near a "bad magnetic influence" area and this is toasting it.

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

The coil and the MSD box are the length of the engine away from each other. How close is close? The coil is in the stock location, and the ECM is right up against the firewall on the passenger side inner fender. Could magnetic interference damage the box from that far away?

Dan, the alternator is a one wire GM 100AMP unit and had an internal regulator. Explain to me how the Alternator affects this. Sorry to sound so dumb here. Any info is potentially helpful.

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The ALT if over charging could fry it, or I seen ALTs go bad and put out A/C voltage, this could fry it. Out side of that I dont think there is any other condision that could fry it, Unless it was plum shorted out & then there would be other major problems.


Injectors, Low Imp & high Imp. Check the OMHs, I think High Imp is around 12 to 14 OMHs & low is around 4 OMHs. (check to be sure).

If putting low Imp on a High Imp system it will fry the Injector Drivers. But if this was the case I would think you would still have Ignition fire.

It is my oppinion that you are frying the Ignition driver cuircut. Either the MSD is wired wrong or it needs a Tach Adaptor.


The TPs being wired backwards as you meantioned should not fry it, if it does I would get a diff brand box. Which at this piont is what you should do anyway. If they charged you $750.00 to fix the last time they will charge you again this time.

Personally I suggest the Big Stuff3 system, it comes with Wideband also.


Jess

well, I might be misinterpretating your post, but seems to me that your ECU and your coil might be TOO close for comfort... I mean, if you have the coil in the stock location (passg side, right below the wheel inner well??? ) and the ecu is above that, it might be causing funny effects. I don't know what kind of electronics does that ecu has, but any hi-tech device could get damaged if you store it permanently near any automotive coil on duty. Also you should run your ECU wires away and apart from any other ignition wires... ir certain wires from the MSD box and certain wires from the ECU are too close interferences may result in misfiring, or ecu malreading parameters...

I wouldn't run a EFI at all on my slant, but if I where to do it, I'd install the ECU inside the passengers compartment (below the glovebox compartment behind the dash, something like that) and would run ground straps stright to the neg side of the battery, not using the body as ground.

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

Mmmmmmmmmmmmdisagree.

Coil, distributor, alternator...maybe.

Starter, starter relay, big firewall connector...don't believe so.

Certainly the starter can cause a big spike across the whole electrical system when you release the key to the "run" position, and that spike could easily damage electronic devices. There should be a large capacitor placed, with a resistor in series, across the large and small starter terminals to damp-out this spike if sensitive electronics are present.

I agree there's going to be a magnetic field in the vicinity of the starter motor when it's running, but there's nowhere to mount any electronics close enough for that to be a problem.

But there's no way there's enough of a magnetic field at the firewall connector or starter relay to cause any kind of interference.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

A lot closer than that. Magnetic interference isn't causing your problem, I don't think.
No.
Where did you get it?
A few ways. GM's internal regulators, from the factory, tend to have ridiculously high setpoints (some of them are up in the 15.2v - 15.4v range!). This is really unacceptably high; it even causes problems on GM's own vehicles. Put such an alternator in a car with equipment not even ostensibly designed for that high of a line voltage, and you're looking for trouble.

Also, poorly-built alternators (materials, parts and/or technique) will tend to have a very "dirty" output. Rather than a steady output voltage, there will be spikes up into voltage ranges that can easily damage sensitive electronics. These spikes can be very hard to see because they can be of very short duration, way too short to see on a digital voltmeter. An analogue voltmeter with needle will sometimes show them, and sometimes you can see them by turning on the headlights and watching for any flicker (though they are not always apparent even then).

Also, alternators in faulty condition (shorted diode) will send really screwy electricity through the line, with reverse-polarity pulses. That'll make scrambled eggs out of sensitive electronic equipment.

I am not certain the alternator is causing your problem, but you almost certainly do not need 100A, and my experience is that these "quick 'n' easy" 1-wire GM alternators can often cause a lot more problems than they solve.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Yep. I'd probably do it that way, too.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

starter and all those last "dont believe so" items... I didn't mean to say that the connector or those components themselves may cause inerference, but if you have a lot of messy wiring, say longer thn usual, or snakeish, that IS a problem for any electronic device.
didn't know... I'll do that on my car
me neither, explained above

Although I don't see how a good 100 amp alt would hurt, I agree on the internal volt regulator part. I'd get a good alt (100 amp you want? be my guest) with an EXTERNAL and output tuneable voltage regulator. That's to say that MAYBE your alternator toasted your ecu 2 times!

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

Although the Alt could very well toast things, unless it just all of a sudden craped(which it could) I really dont think its the problem. He has other electronics that have not up and fried instantly, including a nother EFI system that he run for awail.

But once you run into something like this you cant leave any stone unturned. But I think the box is frying to quick to RF relaited. Now strange running problems, if that where happening then RF would be a good place to look.


Jess


Sorry Sam, I dont kow where you go from here. I have meantioned my thoughts on it already.

Thanks Dan, I will bring the alternator up to the tech at Total performance. The box is grounded directly to the battery. I think it all goes back to the ignition harness, and the "universal" nature of their set up. I started with the dual sync harness,with the intention of eventually going dual sync on this set up, and jury rigged the UIP hook up into that. I did this without a real wiring diagram, but just a verbal discription over the phone from a support tech. I didn't like it then, and I don;t like it now. Trying to use this kit without real wiring diagrams makes it impossible to use any logic in the process. A good analogy would be if you had the task to fix an electric toaster that didn;t work, and you wrote to the manufacturer for a wiring diagram, and the diagram you got back was,"PLUG TOASTER INTO AN AC WALL PLUG".

Accel did not charge $750 to fix the ECM. Total Performance charged $750 for all their diagnostic work, a new coil, and rebuilding the distributor. I dont know what they did to the distributor, but they said it wasn;t working well. I gave them a box of slant six distributors, and they put together the best one possible out of the batch. This I agreed to over the phone, when we thought it was all going to be cool, and not die again. I am not upset with Total Performance. They are doing their best, and were going out on a limb to try and finish up something I started. In the long run it might have been cheaper to let them do the entire thing, including the initial install. It didn't seem that hard to me though. It just seemed like hooking up wires carefully, and then tuning.

The real bummer is that I have now spent close to $2500 on this car, and made it worth essentially nothing now. I think I am getting steamed up enough to write a really blistering letter to Accel. I would never buy this set up again, nor would I recommend it to anybody, almost purely based on the lack of wiring diagrams, documentation, and tech support.
Sam

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Sam,

I am very sorry that this has been such a pain. Without seeing the harness/car, it will be hard to diagnose this problem, although I think Dan has covered most of the bases.

Your injectors are high impedance and should work fine and not draw too much current, unless one or more are BAD. Don't see how that would be the case since they were working with the MS.

I really don't think interference from coil or starter would be a problem, but the alternator could be, I suppose. The ECU should have extensive filter circuitry to protect against that kind of thing, though.

It is pretty ridiculous that Accel does not provide detailed wiring diagrams...

Lou

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Home of Slant6-powered fun machines since 1988

Accel must have wiring diagrams "somewhere" I cant imagine it would be in their intrest to not supply them.

I cringe when I read your posts Sam.....I went through a similar thing last winter when a new mechanic where my vehicles are serviced hooped the harness on my EFI 73 Suburban. Add a vacumm leak to that and the truck was a mess.

I eventually rewired the whole engine compartment....changed out the fried ECU and chip. At least I had GMs wiring diagrams....and the knowledge it had run right before. Since I HAD to have the truck for business the drive to percevere(sp?) was there.

Key for you now will be to analyse the situation and come up with a plan thayt you and Total Performance can execute......cuz Accel wont be much use. Hang in....it will be worth it.

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

There is hope. I went up to Total Performance this morning and talked to them. First encouraging word is their tech REALLY likes the Gen VII system, and promises me that I willk love it once it is done. He also said that Accel will be able to pin point for them, which circuit is getting overloaded, or spiked by which transistor died. The first time, I think they assumed that the trasister was at fault. Maybe a second time the trasister is at fault, but more then likely there is something in my circuit that is causing it to over heat. They did say they have been having trouble witht hat circuit, and mine was not the first one to come back with that part failed.

The other piece of good news is www.Accel-ignitions.com which has wiring diagrams. I haven;t gone there yet myself, but intend to after work. This web site was given me by Fred at total performance. Anyone who is interested might go there and take a peak. It is definately the ignition circuit which is getting fried.
Sam

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