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  #1  
Old 07-27-2003, 09:50 PM
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Danny Burke Danny Burke is offline
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Help Old and new ECU units

ELECTRONIC ECU PROBLEM

I'm in need of a good electronics mopar man. I have a 68 383 roadrunner with and old hemi electronic distributor with and old ECU module. Numbers on back side are 7025218 and on front transistor 034 98809. My problem is none of the new type ECU's
are working when I hook them up. It's like the inner wiring is different. The car won't even start. When I put the old one back in it runs fine but I tried a new ECU from mopar performance and nothing. If anyone out there knows what the hell the problem is write to dannyburke@suite224.net and we'll exchange notes. Thanks in advance

Dan
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  #2  
Old 07-27-2003, 11:12 PM
mtrv8n mtrv8n is offline
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The wiring is slightly different with the new ecu, and you should be using a two connector ballast resistor.
However, the new ecu should work even wired the old way...it may be a bad unit. Yes, it can just be a dud.
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  #3  
Old 07-27-2003, 11:14 PM
mtrv8n mtrv8n is offline
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You might try a parts store ecu, they work fine for a backup, and are not sensitive to wiring changes or the ballast resistor..

BTW, your car had points as delivered, so whatever electronic unit is in there now is already an upgrade.
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  #4  
Old 07-28-2003, 07:41 AM
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Danny Burke Danny Burke is offline
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Unhappy reply

First thanks for the quick reply. Can't be a dud. Tried local store bought ones and ordered direct from mopar performance and still nothing. Had three different one's in car and had a few tested at local shop and they tested good. What were the wiring differences? Have new ballast resistor that works fine. The car runs like a bear with the old one.
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  #5  
Old 07-28-2003, 06:44 PM
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ehostler ehostler is offline
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Is the exisiting ECU a 4-pin or 5-pin ECU?? You cannot interchange them and expect it to work. If you pull out a 5-pin, it must be replaced with a 5-pin. If you pull out a 4-pin, it must be replaced with a 4-pin.
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  #6  
Old 07-28-2003, 10:46 PM
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Yes, have replaced with same number pin unit. Mopar restoration book makes quote of running a gray-tan wire to negative post of coil while running a dark blue wire from positive post of ballast resistor except with the hemi where it was wired into the alternator wiring harness. Page 246 and that the early and late distributors are not interchangeable. No late models should use a Prestolite-built unit, page 247 of Authentic Restoration Guide by Paul A. Herb MBI Publishing Company/
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  #7  
Old 07-29-2003, 02:28 AM
George G. Leverette George G. Leverette is offline
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The 4 pin and 5 pin are completely interchangeable, been there done that, makes no difereence. The two blade and 4 blade ballast resistors will also interchange done this also with success. This refers to the late model ECUs from any source. The Mopar ignition is a good one but will not provide the performance and especially the realibility as modern units on the market at slightly more cost. MSD is one way to go.
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  #8  
Old 07-29-2003, 10:25 AM
Blaine Peterson Blaine Peterson is offline
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Danny,
Don't know if I can help with your problem but I am curious, maybe even confused about a few things.

First: why do you think your dist. is from an old hemi?
Second: how did you get the RB dist. to work with your B engine?
Third: if the engine runs fine with the old ECU, why do you want to replace it?
Forth: what did you mean when you said "the car runs like a bear with the old one"? Is that a good thing or a bad thing?
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  #9  
Old 07-29-2003, 11:36 AM
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71383bee 71383bee is offline
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I just did this swap the other weekend it is very easy as long as you have the correct distributor. One thing I find confusing is that you say you use an old hemi distributor and you are in a 68 RR? I thought electronic ignition became available in 1971. The old hemi distributor were dual points units I thought not electronic? I am just a little confused. What type of balast resistor are you using? Is it a 4 pin or a 2 pin?

There are basically 2 wires to hook up one black w/ yellow stripe to the <-> on the coil and one blue to the blue wire on the balast resistor which is hot when the key is in run. The green wire is clipped off. The other two should be already formed into a double bullet connector which connects to the distributor.
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  #10  
Old 07-29-2003, 02:23 PM
beepbeepsrule beepbeepsrule is offline
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Make sure the case of the ECU is grounded properly.

The 4 and 5 pin units do interchange assuming the wiring truly is correct.

I can only assume you have a spacer under the distributor and that is how a hemi distributor is working in your 383.
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  #11  
Old 07-29-2003, 04:28 PM
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Default Hope this will clarify all questions

Will try to answer all of your questions. (Blaine and others) Mopar performance now and in the past made a adapter spacer used with the 71-72 Hemi Dart distributor. Still offered my Mopar performance in their catalog. It allowed the longer shafted electronic distributor from the hemi to be used in a big block 383-440 by raising the shaft about an inch and a quarter. This allowed the new electronic ignition systems offered with the 1971-72 --340's and 426 hemis to be intergrated into 383-440 blocks. The older version, made by Chrysler, had a cable driven tach (Moroso) which I believe was first intoduced by Chrysler and later by Prestolite. The problem I'm having is the car comes out of the hole really well until at about 4000 RPM the car starts to break up until I shift (automatic trans)into 2nd. I'm running 440 heads with a six-pack. The distributor has no vacumm advance and the six pack is manual and has no vacumm secondaries. If I time car to correct specs. car will not idle correctly unless pushed to the limits by advancing it well off timing mark. I have no knowledge if a higher lift cam was installed (because of no prior owners info)but car runs best way off timing mark. About 1/4 turn around balancer. It appeared as though it was not getting enough spark at higher RPM's. Tried new electronic distributor and mounted correcdtly in car but back fired spit and sputtered as though it was 180 out of sink. Put in old distributor back in as I did the newer distributor and car ran great until it reached higher RPM's. So I went with a few different ECU and finnally a gold Mopar ECU to 10,000 RPM but car wouldn't even start. Called Mopar tech support who stated wiring was different in that ECU. Waiting for copy of wiring diagram coming in the mail in a few weeks. So I decided to ask those of you out their if anyone may have encountered same problem. I assumed as others have stated that they were all the same and I could just bolt it in. But I've tried stock ones and racing ones and none of them will work with this distributor. That's the story to this point. I save the destruction a this nice RR after the jerk that owned it was launching a boat with it, didn't know how to shift it with a manual valve body transmissionand had the timing so far off that the car couldn't beat a Ford. It's been a nightmare trying to find all of the screw ups this guy made with this car. Been working on it whenever I have spare time and money. It's a labor of love on my behalf. Will work on body and paint when I get it mechanically running well. Thanks for all of everyone comments. Writing it all down and trying everyones suggestions.
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  #12  
Old 07-29-2003, 05:03 PM
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ehostler ehostler is offline
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The stock (black) ecu and the performance (Orange, Chrome, and Gold) ECU all use the same pinout. They guy on the phone was clueless.

The adapter that you mentioned is to adapt an RB distributor into a B block.
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  #13  
Old 07-29-2003, 05:39 PM
beepbeepsrule beepbeepsrule is offline
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I can't help without suggesting things that will cost more money, sorry!

At this point I would convert back to a stock-type MoPar electronic distributor, ECU (chrome), MSD Blaster2 coil and rewire to specs.

(You may want to convert to a 2 wire alternator and '70 and up electronic voltage regulator. The MoPar electronic ignition setup likes that a little better than the older setup. Not a difficult upgrade if you can read wiring diagrams. Also not necessary to just get it running, just a good thing to upgrade to for reliability.)

It also sounds like the distributor drive gear may not be clocked correctly. The previous owner may have just moved the spark plug wires around on the cap rather than re-clock the drive gear. Not too big a deal until you try to undo what they did.

I cannot visualize the distributor you are talking about, it may be completely unique to that strain of engines, all unique internals. That would make the wiring funky I guess if it used a different type of pickup method.

All MoPar electronic distributors I have ever seen all use the same internals. The pickup coils and reluctors are the same, although the reluctors do have two keyways to choose from for the install. One is for clockwise rotating distributors (small blocks) while the other is for counter-clockwise rotating distributors (big blocks). (One of the keyways is marked with a direction arrow). When the incorrect keyway is used one of the symptoms is that it launches good but RPM seems to be limited to about 4000 rpm.

I would definitely re-wire the ignition. The previous owner could have mixed up the polarity on on the pickup on the inside then fixed it by swapping the connections around on the harness, who knows!
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  #14  
Old 07-30-2003, 09:44 AM
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71383bee 71383bee is offline
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Well if you are getting different results when you change distributors then i would sugest that each individual distributor has different mechanical and vacum advance amounts. If it spits and sputters with a stock style distributor with VA then I definately think you have a larger cam and/or higher compression and the VA unit is advancing it way too much. Do you have an advance timing light or timing tape on the dampener? The MP hemi distributor seems to be a higher perfromance unit that has a curve that is more apealling to your combo. This whole thing sounds like a timing issue to me.

Do yourself a favor and DO NOT call that goof at Mopar Performace again! There is no difference in the wiring between the Orange, Chrome, or Gold boxes. If you are going to stick with a MP ignition the chrome box is the prefered choice for street/strip cars. The Gold box is meant for strip only and it has a very limited life span. I use a 4 pin box from Carquest and it seems to be a decent unit LX-101 I beleive. If you need to speak to someone from Mopar Performance call Cal Anderson at Hub Chrysler Jeep in West Allis WI his number is on cuda's phone list stickyed at the top. He is an enthusiast and he sells MP parts for cheap.
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  #15  
Old 07-30-2003, 03:53 PM
Blaine Peterson Blaine Peterson is offline
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You haven't given us too much information on your engine or how much time the car spends at the track verses the street but I'm thinking if it had a big cam and other modifications you'd be able to tell.
Based on that I'd think seriously about what beepbeepsrule suggested. Make sure the dist. drive gear/intermediate shaft or whatever Mopar calls it is in right (find TDC on #1 of comp. stroke, line up the marks.....you know the routine), and I would probably pick up a new Electronic Ignition Package from Mopar Performance and install it. Probably would go for the one designed for the 383 (B) engine, but since you already have the RB to B adaptor I guess the RB dist. might be the way to go, just in case down the line you wanted to drop in a 440 or 426 Hemi then you'd allready have your distributor. Anyway, I think you need to look at the basics then go from there.

And upgrading to the '70 and later alternator and electronic regulator as already mentioned is a good way to go.

Something else you may want to consider is buying the Mopar ENGINES book that Mopar Performance sells. Its helped me out a few times in the past, and is good to have around for all the reference info included. Cost is around $30 but worth it IMHO.
Hope this helps, and keep us posted on your progress with your Bird.
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