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| MSD question https://www.slantsix.org/forum/viewtopic.php?t=28714 |
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| Author: | SlantSixDan [ Sun May 04, 2008 9:35 pm ] |
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Quote: Just hook the tach wire up to the negative post of the ignition coil.
Yep. The only reason the MSD box needs a special dedicated tach feed is because the multi-strike output foozles the tach.
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| Author: | emsvitil [ Sun May 04, 2008 10:02 pm ] |
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Quote: Quote: Just hook the tach wire up to the negative post of the ignition coil.
Yep. The only reason the MSD box needs a special dedicated tach feed is because the multi-strike output foozles the tach.That's not the only reason......... A MSD is hooked to both sides of the coil and supplies about 400 volts to the coil instead of the normal 14v or so of a standard ignition |
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| Author: | Sam Powell [ Mon May 05, 2008 7:23 pm ] |
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Thanks guys. I will look up the HEI threads and go in search of the needed parts, and gt that going. It is way cheaper than a new MSD box. You know, the only thing that changed besides the ECU when I switched from MS to Accel was the coil. I had one of those enormous Accel coils that is big and square. I wanted to go with a smaller part for space reasons. I think they were actually originally designed for a farm tractor application, and Accel boxed and labeled it as a performance part. Anyway, I purchased a new Blaster coil to install with the new Accel ECU, and I accidentaly knocked it off the bench before I could get it on the car. Consequently I s***canned that part and just went out and purchased a standard supply house coil. So, since all other parts on the car were working fine with the MS ECU, wouldn;t that be a reason to suspect the coil? I know it is really tempting to suspect the ECU calibration, and the tuning, since that is all different, but I never really did much tuning on the MS, and it at least ran. Lou drove around with me a couple of times tuning the fuel map, and that was about it. Of course, the wiring later became suspect as well, but this never really presented itself as a problem until I changed over to the Accel ECU, and changed the coil. Any recommendations for a coil to go with the HEI? Thanks again guys. I have been so pre-occupied with fixing this garage roof that I have spent almost no time thinking about this. I am glad you were willing to. Sam |
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| Author: | SlantSixDan [ Mon May 05, 2008 7:27 pm ] |
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Stock/standard coils often don't play well with high-tech ignitions. see The HEI upgrade instructions include a couple of different coil suggestions. |
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| Author: | rock [ Tue May 06, 2008 10:33 am ] |
| Post subject: | Sam, I use an E core MSD coil |
Sam, You might want to look into E core coils. I use the MSD one with the dizzy connector like a sparkplug. I wanted the separation it gave me between the leads and the dizzy wire because I was able to drive the standard coil format until it arced. Seems it is about 43 bucks new and works like a charm for me. After my experiences I got wary of standard core coils. Just me, I know millions have no problems, but I attract them. rock '64d100 |
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| Author: | Sam Powell [ Wed May 07, 2008 4:00 am ] |
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I read the thread on the HEI conversion, and looked at the Accel install instructions, and am confronted with the same frustration that has reared its ugly head with the Accel from the start. I'm just not smart enough to do this with the info I have. The Accel diagrams are not wiring diagrams but plug and play wiring harness instructions. There is no diagram of the ignition harness internal wiring for the HEI. They have several different HEI harnesses available, but absolutely no information as to what wires are hooking up to what pins from the ECU harness to the HEI module. The MSD box is fired by a single white wire from the Accel ignition harness. And the coil is charged and fired by two wires from the Accel box. Since the HEI is hooked up to TWO wires from the distributor, and I have only one wire coming from the ECU to do this, I don;t know how to wire it up. Any ideas? Thanks for taking your time to help a self confessed electronic dumb dumb. SAm |
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| Author: | rock [ Wed May 07, 2008 7:19 am ] |
| Post subject: | Sam, here is an idea |
Sam, I am not the electronic wizard that 2 other fellows on the forum are, and of course here you go...BUT....I put months of thought into the wiring solution for a triple ignition system....HEI, MSD, and Pertronix all wired in and able to switch in as needed or desired AND using an internally regulated GM alternator. In doing that work I decided it was best for me to run new wires I absolutely knew the origin and end of. If you can fax or scan and email the Accel diagram to me (send me a PM for my email address or fax) I would be delighted to look at the diagram and see how it mates to what I have learned of slant wiring. I could do you a sketch and email back. I "think" wiring diagrams and they are particularly useful when trying to connect to the stock ignition switch, because we have Ign1 and Ign2 on the back, and I call them "only on when starting" and "only on when running". Of course ACC is also "on" when running. When you turn your key to start ("on when starting") Iyou are removing part of the charging circuit to power the ignition circuit and once you are started and release the key to run, you are operating the part of y our circuit that keeps your battery from overcharging. If you take out your switch and study the back against your FSM diagram, the logic of how it works is clear and you can then readily rewire to what you want to do. Make your own diagram of what you have stock by tracing wires with a VOM and make a dagram of what you want to do. It teaches you quite a bit about auto electricity. I have never looked at an Accel box but you can bet it has an "in", an "out", and a ground, and most likely a tach conncection somewhere. Well, so does your stock ignition circuit. rock '64d100 |
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| Author: | KBB_of_TMC [ Wed May 07, 2008 9:41 am ] |
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I have 2 MSD 5's - one has run fine for years, the other developed a glich only when it was colder than around 32F; above that temperature, it ran fine, below, it fired very erratically. I took it apart, but could never pinpoint the problem (at least while working at room temperature). I've often seen electronics that would mysteriously start or stop working at a particular temperature. People often use hot air guns and cooling sprays to find such problems, but I didn't bother. Just FYI, I also found that the 5V signal off the points when using the MSD worked very well to run my very old Stewart Warner Stage I tach, but not the newer models I tried. Maybe it was designed to work on 6V systems too? |
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| Author: | Sam Powell [ Fri May 09, 2008 7:35 pm ] |
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Rock, YOu can find the diagrams for Accel on line. http://www.accel-dfi.com/AskTechKnowled ... ?BrandID=8 This is the tech line, and I think there is a link somewhere there to the instructions for their entire line. I will look elswhere later to see if there is another address. KBBm I really appreciate your telling me your experience with the temp sensative MSD. This is useful info, and suggests it is ast least possible this is what is going on here. This box is 15 years old, so maybe has lived it's useful life. Sam |
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| Author: | Matt Cramer [ Sat May 10, 2008 5:53 am ] |
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I'd accidentally posted this in the wrong thread, but here's one possibility: Can the Accel box fire a coil directly, using the same line that would connect to the MSD box's white wire? Often systems that have built in coil drivers use them when connected to an MSD box, but I don't know if your system has a coil driver in it or always needs an external module. |
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| Author: | Sam Powell [ Sat May 10, 2008 6:29 am ] |
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The Accel system requires an external coil driver. They warn repeatedly that drying to drive the coil directly will destroy the ECU internals. Some folks apparently try this in spite of the warnings as they say the warrantee will be voided by doing so. It is a logical thought though. Sam |
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| Author: | Matt Cramer [ Sat May 10, 2008 11:36 am ] |
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I'll bet you can get it to drive some other sort of external module that uses a similar signal. There's a couple of Bosch modules that are pretty popular in the Megasquirt world that don't require a second output like the computer controlled HEIs, for example. |
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| Author: | Sam Powell [ Sat May 10, 2008 11:45 am ] |
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Do you have either a web site, or part name to search for? Do you guys sell an appropriate ignitioin module? Sam |
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| Author: | SlantSixDan [ Sat May 10, 2008 11:53 am ] |
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Quote: I'll bet you can get it to drive some other sort of external module that uses a similar signal. There's a couple of Bosch modules that are pretty popular in the Megasquirt world that don't require a second output like the computer controlled HEIs, for example.
Y'mean...like...the non-computer-controlled, regular 4-pin HEI module, for example? 
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| Author: | Sam Powell [ Sat May 10, 2008 7:30 pm ] |
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Dan, How would I wire the standard 4 pin HEI module? Do you have an application I can reference at the parts store? I would promise not to ask any more dumb questions, but I like to be able to keep my word. Sam |
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