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My new electrical nightmare
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Author:  6inarow [ Mon Aug 11, 2014 7:54 pm ]
Post subject:  My new electrical nightmare
Hey everyone,

I just recently purchased a 1986 D100 with a \6 to drive every day. Purchasing the truck for a mere $700, I didn't expect much. Unfortunately, I got more than expected in the way of wiring.

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The truck ran absolutely terrible on the way home, but it did happen to make it there. Upon further inspection I noticed multiple broken studs in the head causing intake\exhaust leaks, and a nightmare of random, poorly done wiring. The head is off the truck now getting the studs drilled\tapped out and checked over.

I've been researching a bit on the wiring (just burned the haynes manual), and happened to come across the "spark control computer". Apparently it's a nightmare, and I'd like it gone, but I'm coming across a lot of conflicting information and broken links. I need this thing as reliable and simple as possible, so if it isn't needed or reliable, I want it gone!

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Author:  Reed [ Mon Aug 11, 2014 10:33 pm ]
Post subject: 
Switch to an HEI ignition and a non-lean burn carb. Use the fat black wire that powered the computer to power the HEI unit.
Author:  6inarow [ Tue Aug 12, 2014 6:08 am ]
Post subject: 
Quote:
Switch to an HEI ignition and a non-lean burn carb. Use the fat black wire that powered the computer to power the HEI unit.
I found some videos on the HEI conversion shortly after posting this, looks like that is the best option. Is there anything that makes my carb non-functional without lean burn? It's freshly rebuilt.
Author:  nuttyprof [ Tue Aug 12, 2014 6:11 am ]
Post subject: 
Quote:
Switch to an HEI ignition and a non-lean burn carb. Use the fat black wire that powered the computer to power the HEI unit.
x2
Author:  wjajr [ Tue Aug 12, 2014 7:04 am ]
Post subject: 
Among other possible differences incompatible with stock pre Lean Burn ignition system, the two main differences would be Lean Burn carburetor has no provision for operating a vacuum advance pod that is attached to that new distributer you will be installing, and additionally LB distributor has no mechanical advance weights. Vacuum and mechanical advance is key to drivability and good fuel economy in a street driven car.
Author:  6inarow [ Tue Aug 12, 2014 7:27 am ]
Post subject: 
My current carb has a provision for the "osac" valve according to the Haynes manual. Can I run that straight to the vacuum advance? I'm starting to realize this truck has so many mismatched parts.
Author:  Reed [ Tue Aug 12, 2014 7:41 am ]
Post subject: 
Ignore the hanes manual. Your truck did not have a OSAC valve because timing was computer controlled. As has already been mentioned, the stock lean burn likely has no provision for ported vacuum advance (no vacuum at closed throttle) that is necessary for optimal street operation of the engine.

You need to get a factory service manual for your truck.

Go to the FAQ sticky thread in the electrical section for the instructions of how to convert to HEI ignition.
Author:  6inarow [ Tue Aug 12, 2014 8:46 am ]
Post subject: 
The truck came with a two barrel carb and intake mani, I'm assuming these will swap over with little effort. It's a Holley unit, I'll try to get the numbers and source a rebuild kit since it's in pieces.

I have most of the parts already for the HEI swap already. Thanks for all the info!
Author:  Reed [ Tue Aug 12, 2014 9:33 am ]
Post subject: 
Hopefully the Holley is a 2280 and not a lean burn 6280. Look for wires going into the float bowl. If there are wires going into the float bowl, it is intended for use with a computer. Hopefully the carb will have a ported vacuum nipple for the vacuum advance for the distributor.
Author:  xjarhead [ Tue Aug 12, 2014 10:12 am ]
Post subject: 
Hope this will help.

Recently while I was rewiring my truck, I took the time to rewire the HEI module that I converted to a few years back.
I also took a picture of it.
I wanted to mount this in the original location of the Lean Burn computer. The engineers designed the computer housing to hook into the air intake for the engine to help with keeping the computer cool,
so I thought it would a good place to help keep the module cool.
Well I disassemble the computer and found that after pulling the electronics out of the housing I was left with an 8 3/4 inch X 4 inch area for a heat sink. So I picked up a piece of 1/4 in aluminum plate to fit in the housing, shouldn't have any heat sink issues. Some would say that I went thru allot of trouble to mount this module. But the housing is designed with 2 openings one where air is drawn in by the other opening that is connected by a hose to the breather intake hose, there by drawing cooler air across the entire inside of the housing. I have been driving it like this since 2007 and have not had any issues.

Here is a picture of the rewired module and ready to reassemble.
https://skydrive.live.com/redir.aspx?ci ... 6xyhouBGNQ

I kept the vacuum advance pod in there just to plug that hole. Make note of how the pod is orientated when you pull the 2 halves of the housing apart, or it will not go back together easily.
https://skydrive.live.com/redir.aspx?ci ... 8yvF3fYYso

all the wires I used when I did the conversion were all there plugged into the computer. There were 2 wires going to the coil, 2 to the distributor and 1 ground wire.
Here is a link to a PDF of the wire diagram from the factory service manual and wires highlighted that I used.
https://skydrive.live.com/redir.aspx?ci ... s12eOvYLZI
doing this mod I was able to eliminate 15 wires from my wire harness.
I used a 6 pin GM weatherpack that I got from junk yard for $2 to make all the connections. Weatherpack is so that it will disconnect from main harness for removal if any repairs are necessary. Do not attempt to buy this weatherpack new from NAPA just the blank housings are $15 apiece!!!! By the time the guy had figured all the pins and seal I would have had $45 in just one six pin connector. I found mine on a K5 blazer for $2. I was able to reuse most of the seals and bought new pins as needed. I think I ended up with $10 or less invested in the connector.
Originally when doing the conversion I had tried using a dizzy out of 73 dodge truck. It had to much mechanical advance, 30 degrees total if I remember correctly. Grab one from a 78 Volare with Super Six setup and it made huge difference. I also used the Blaster 2 coil as in the article. There was no ballast resistor either.
Hope this will help.

Dave
Author:  6inarow [ Tue Aug 12, 2014 12:38 pm ]
Post subject: 
Quote:
Hopefully the Holley is a 2280 and not a lean burn 6280. Look for wires going into the float bowl. If there are wires going into the float bowl, it is intended for use with a computer. Hopefully the carb will have a ported vacuum nipple for the vacuum advance for the distributor.
Here they are, in all their glory. The two barrel on the left appears to be a 2280 from a super six truck I am told. The carb on the right is what I'm assuming to be a Holley 1945 since it has no provisions for a distributor.
I need to source some more parts to get this carb to work on my truck since I only have the carb and intake manifold. The search begins!
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xjarhead, really great info, and I really like how you retained the factory box for the HEI conversion. Will probably be taking this route when I start my swap!
Author:  Reed [ Tue Aug 12, 2014 12:47 pm ]
Post subject: 
Quote:
Here they are, in all their glory. The two barrel on the left appears to be a 2280 from a super six truck I am told.
It would have to have been a very late truck for it to have gotten a 2280 form the factory. Chrysler did eventually install the 2280 as a factory carb, but this was in the early 80s, at the very tail end of Super Six availability. Looking at the picture, it appears that you have a 318 2280. The choke linkage is the giveaway.
Quote:
The carb on the right is what I'm assuming to be a Holley 1945 since it has no provisions for a distributor.Image
Not true. Do you see the vacuum port directly behind the big PCV port? That would be the vacuum port for the distributor IF it is ported (no vacuum at idle with the throttle closed). You can see if that port has vacuum at idle in two ways: (1) install the carb and hook a vacuum gauge to the port with the engine running; or (2) flip the carb over and see if the hole for that port in the throat of the carb is above or below the throttle blade. If the hole is above the blade, then it is a ported vacuum port for the distributor. If the hole is below the plate then it is a full-time vacuum port for the computer.

Try runnign that 1945, it looks promising. Worst case scenario is you run it and just cap the port for the vacuum advance if it isn't ported. You can run the truck without vacuumadvance untilyou get all the right parts gathered to convert it correctly.
Author:  6inarow [ Tue Aug 12, 2014 1:07 pm ]
Post subject: 
It's below the throttle body unfortunately, but I did notice the port above the pcv shoots directly into the body above the throttle, confirmed by passing some wire through it. I'm going to guess this isn't going to work for some odd reason, haha.

Also noticed upon removal of the spark control computer that it has an additional 14 pin connector. Do I need to retain any of this? I was only aware of the 10 pin.
Author:  Reed [ Tue Aug 12, 2014 1:21 pm ]
Post subject: 
If you take the time to trace every wire in the loom for the computer, you will find that the wires go to various sensors on the engine, the distributor, the coil, the carb, a big fat ground terminal, and a couple fat black positive feeds. You do not need to keep any of the wiring for the computer but be careful dealing with the positive feeds as they are switched leads and must be properly insulated when abandoned.

Converting a lean burn vehicle to HEI is very simple. You can either use one of those black fat positive feeds for the computer to power the HEI relay or you can use the coil (+) terminal as a tap for the HEI relay (+) feed. The lean burn systems do not have a ballast resistor so if you use the coil (+) as the feed for the HEI relay you can install the HEI module VERY easily. Two wires to the coil, two wires to the distributor, ground it, and you are done. Easy-peasy.
Author:  Reed [ Tue Aug 12, 2014 1:22 pm ]
Post subject: 
Quote:
It's below the throttle body unfortunately, but I did notice the port above the pcv shoots directly into the body above the throttle, confirmed by passing some wire through it. I'm going to guess this isn't going to work for some odd reason, haha.
Wait- when you stuck a wire through that small port the wire cam out into the carb throat above the throttle blade? If that is what happened then the carb will work with a vacuum advance distributor.
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