Rewiring my EFI Magnum - 1970 Dart Swinger

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autopar3000 said:
It runs!!! All I did was turn the key on then off a couple of times, which primes the fuel pump. Then set up the camera and... super fast start up, just like normal. I was later thinking I should have had the belt on it so see if the charging wiring is OK, but I'm sure it will be fine. I hope it will be fine.

I don't usually take video, or even pictures when I'm working on the cars. Only if I need to remember how something came apart. This very much felt like one of those "will it run?" videos you see on car builder shows. "This thing better start or we're going to lose the shop!!!" Lol, looks like the shop is safe for now.

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Nice job getting it fired up. Looking forward to more updates.
In post three you had a serpentine belt installed but it looks tight at the water pump. If that is still the power steering bracket from the van the belt is probably rubbing, or will when running. Is that car going to get air conditioning?
 
Bobzilla said:
Nice job getting it fired up. Looking forward to more updates.
In post three you had a serpentine belt installed but it looks tight at the water pump. If that is still the power steering bracket from the van the belt is probably rubbing, or will when running. Is that car going to get air conditioning?
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I have actually had this setup running for a couple of years, and it doesn't rub; there's about a half inch of space. If you look closely at my idler pulley you'll see it's smaller than the usual Magnum idler. I don't know why it's different from the normal pulley, but that whole setup including the power steering bracket cam from the van. Maybe the conversion company put that on there? It had a monster alternator on it that had an external voltage regulator wired in, I'm assuming done by the company that converted it to an ambulance.

When I was at the pick and pull getting my Ram relay box I wanted to get an earlier style cruise servo too. Turns out the truck in the yard was a stripper model and didn't have cruise or air conditioning, so I ended up grabbing the non-AC bracket which has the standard size Magnum pulley.

I do plan to put AC in the car eventually. Probably. OK, maybe. For now I'm going to get it back together without AC. Not sure if I'm going to put this non-AC bracket on now or do it later in the summer. I might do it if I decide to swap out my 180° thermostat for a 195° unit. I have a manual control on my electric fan and I have noticed the engine actually runs way better when I let it get hot, but I want to install external transmission cooler before I move to the 195° thermostat.


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Taking a break from wiring. With my old setup I had the electric fan control, OD switch, and check engine light hiding inside the console ashtray:

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For my new setup I want to put my cruise buttons, OD button, and fan switch in there. I'll figure out something else for the check engine light, if I even bother with it. These buttons are pretty wide so I had to hog our the ashtray mounting area a little.

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autopar3000 said:
I have actually had this setup running for a couple of years, and it doesn't rub; there's about a half inch of space. If you look closely at my idler pulley you'll see it's smaller than the usual Magnum idler. I don't know why it's different from the normal pulley, but that whole setup including the power steering bracket cam from the van. Maybe the conversion company put that on there? It had a monster alternator on it that had an external voltage regulator wired in, I'm assuming done by the company that converted it to an ambulance.

When I was at the pick and pull getting my Ram relay box I wanted to get an earlier style cruise servo too. Turns out the truck in the yard was a stripper model and didn't have cruise or air conditioning, so I ended up grabbing the non-AC bracket which has the standard size Magnum pulley.

I do plan to put AC in the car eventually. Probably. OK, maybe. For now I'm going to get it back together without AC. Not sure if I'm going to put this non-AC bracket on now or do it later in the summer. I might do it if I decide to swap out my 180° thermostat for a 195° unit. I have a manual control on my electric fan and I have noticed the engine actually runs way better when I let it get hot, but I want to install external transmission cooler before I move to the 195° thermostat.


View attachment 1716220935
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Interesting on that smaller pulley from the donor truck. That non-AC alternator bracket is a good find. Did you grab the heater tube spacer as well? It supports the heater tube when the AC portion of that bracket is not there.
 
Bobzilla said:
Interesting on that smaller pulley from the donor truck. That non-AC alternator bracket is a good find. Did you grab the heater tube spacer as well? It supports the heater tube when the AC portion of that bracket is not there.
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I did not grab the heater tube spacer! Makes sense that it's needed. If I use that bracket I guess I'll have to figure out something for that.
 
blind bat said:
Nice Supra!
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Thanks!! Ha ha, turns out you're not blind after all :D

It's a fun car. Surprisingly good in corners considering the 14 inch tires, braking is excellent, but S-L-O-W. I'm not bothered by that, 160 HP was the best you could expect from a 2.8 liter 6 cylinder at the time. I could swap in a later engine and double the horsepower, but I'd prefer to put that time and effort into the Dodge.
 
I need opinions!

I got the plastic base plate all shaped and drilled and it came out OK. I made it out of an old otterbox tablet case, so the plastic has a good texture and is strong.

Which setup do you guys think is better? OD button with the cruise control buttons, and fan switch in where the lighter would be? Or fan switch with the cruise buttons and OD in the lighter hole?

In the picture on the left the fan switch is not seated because I would have to increase the size of the hole a litte. It's sitting about flush with the buttons on the left but if I put the switch in there it would be down about 1/2 inch.

Console comparison.jpg
 
I like it with the fan switch in lighter spot. Just a thought, keep the fan on all the time and when you turn on OD, the switch can also turn fan off since when in OD you're at speed with good air flow and not needed. make the fan switch to turn off fan if wanted then when you have AC added you won't have to change the wiring to have fan on at low speed to move air across condenser.
 
I would keep the OD button with the CC buttons. Feels more organic, natural, to me. Just my opinion.
 
Thanks guys, so far it looks like 2 votes for the left picture.

@moparlvr166 those are some good thoughts about the fan, but it's actually on an adjustable thermostatic switch / relay. I have it set to come on at about 210° and it shuts off at about 200° but since I have a 180° thermostat and I rarely drive in traffic, the fan doesn't come on very much. It's not wired through the ignition so it can turn on with the key off, so the switch just allows me to kill power to it. Sometimes the fan will come on after I shut the car off and I might want that to happen. Other times I don't want that to happen, so I hit the switch. When (if) I install AC I'll have the fan come on with the AC, but having it shut off when OD kicks in is genius, thanks for that idea.
 
Any more opinions on how I should configure the buttons and switch?

I spent way too much time last night figuring out how the cruise switches need to be wired. This is the only case where the 1994 Ram factory service manual has failed me. The wiring schematics (there are 2 drawings) for the vehicle speed control system don't show exactly how the factory switches are wired, and in some respects what it does show is incorrect. Also, the troubleshooting section for the factory switches doesn't say which wires go to which connector pin; it just tells you which pins should have continuity.

After literally hours of messing around and looking through the manual for some clues, I came across this little image in the EFI section that shows a simplified diagram of how everything connects to the PCM. This stupid little diagram showed me exactly what I needed; how the switches are wired together, which ones are normally open, and which ones are normally closed.
:mad:

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Confused by the resume button. Doesn’t look like it ever connects to power.
 
I'll be running all the extra wires through the hole that's for the manual washer pump. I got a big grommet to keep the wire insulation happy, and I'll be putting connectors on everything, as opposed to hardwiring, so I can pull it apart and easily put it back together if I have to.

I bought these knock-off Deutsch Connectors and I'm really happy with them. They will be on the other side of the grommet inside the cabin so weatherproofing is not really necessary, but I needed something that would support 10 wires and fit through the 1 3/8 inch hold in the firewall. The 8 pin and 4 pin connectors from the kit are perfect.

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Leaving one empty on this connector for now until I figure out the tach situation. It seems the Magnum PCM sends a signal with half the pulses my tach is expecting. I had a guy tell me he put his aftermarket tach into 4 cylinder mode and it worked, but I don't know if my tach has that option. I have the rallye dash tach from Classic Industries, which might have been designed to only work with 8 cylinder engines.
https://www.classicindustries.com/product/ma1525.html

I can pull off the cluster and have a look at it, or I can just splice the tach wire into coil positive like I had done before. Does anybody know if that tach has the switching for 4 cylinder mode?

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The brake switch took some time to figure out. I'm sure you guys are familiar with the standard A body switch and bracket:

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The more modern Chrysler brake switches tend to have a square mounting hole, like the one below.

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I didn't really want to re-engineer the bracket, so I'm going to use this. GM brake switch from the 1990s. It has 2 terminals for the brakes, 2 for the cruise, and I think 2 for ABS. That's what is on the Dodge brake switches, and the switching is the same: 1 normally closed for the brakes, and 2 normally open for the cruise and ABS.

The key thing for me is that the round threaded part fits through the round hole on the A body bracket. It also helps that I was able to order the connectors, although I didn't order the 2 prong connector for the brakes. It was $35 which I think is a bit much, considering I can use standard spade terminals basically for free. And the switch itself only cost $8! The 4 pin connector, which has much smaller terminals and would therefore be harder to jerry rig, was "only" $25.


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I decided to get rid of that plastic retainer and instead I sandwiched it between 2 nuts. I was pretty surprised to find those threads are standard and not metric. 1/2 - 20, in case anyone else is thinking about this solution.

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autopar3000 said:
I didn't really want to re-engineer the bracket, so I'm going to use this. GM brake switch from the 1990s. It has 2 terminals for the brakes, 2 for the cruise, and I think 2 for ABS. That's what is on the Dodge brake switches, and the switching is the same: 1 normally closed for the brakes, and 2 normally open for the cruise and ABS.

The key thing for me is that the round threaded part fits through the round hole on the A body bracket. It also helps that I was able to order the connectors, although I didn't order the 2 prong connector for the brakes. It was $35 which I think is a bit much, considering I can use standard spade terminals basically for free. And the switch itself only cost $8! The 4 pin connector, which has much smaller terminals and would therefore be harder to jerry rig, was "only" $25.


View attachment 1716226879
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I used an F-Body brake switch when I did my CC retrofit, but everything else was F-Body as well so it made sense. Worked with the stock bracket and gave me a NO brake light switch and a NC CC switch. No idea how many circuits you need though so not sure it is another option.

I should add that best I can tell you can't buy the F-Body switch anymore, so finding a option like you did might be the only path now.

Cool thing for the G3 swap is, I think I just have to send a 12v signal to kill the CC so the single connection on the stock switch should work for me. But more researched needed as I've only looked that topic over quickly and might be missing something.

I did grab a brake switch out of an early 90's Dakota for the clutch switch though. It has 3 circuits (I think) and pretty sure it used the same round threaded mounting setup as the stock brake switch and the GM switch you are using.

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Just other ideas.
 
I did look around for vintage Mopar brake switch options and found there wasn't much that was available for cruise control anymore, but I quickly stumbled across the GM option and didn't keep looking. I think that Dakota switch would work though! The G3 system makes a lot more sense, you can use just one switch for the brakes, cruise, and whatever else, instead of the 3 switch system used through the 80s and 90s. I guess the auto makers were slowing implementing computer controls and still felt comfortable using mechanical switches for some things.

The Magnum setup need two normally closed switches, one is used to cut power to the cruise servo and the other is a signal to the PCM (plus a normally open for the brakes). I'm not sure how the PCM uses the input for the cruise system (aka speed control system), but it's also used for other functions. Or maybe it's more accurate to say I'm not sure why one is used to cut power to the cruise servo when the PCM could manage that.

Here's the FSM piece about the signal to the PCM:

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I got the brake switch all wired in and tested. Still not sure about the connector for the brake lights, I might drop the $35 and buy it. Probably not. I also got all the wires run under the carpet towards the console. The blue wire you see is my shift indicator light, and the red one is ignition power I was using to run the OD and lockup. I still need those and I didn't feel like messing with them, so I left them alone.

But the power wire won't be used for the transmission anymore. It was going through the floor to the transmission, but with the new harness I'll have the transmission wired up more like a factory Magnum setup where the wires run over top of the transmission from the engine bay. I'll be using the old power wire to power the cruise system and the lights for the switches in the console.

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autopar3000 said:
Still not sure about the connector for the brake lights, I might drop the $35 and buy it. Probably not.
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If it was me, I would go to a wrecking yard and clip the plug off whatever GM model the switch came from. I would bet you could even de-pin it and slide your wires right into it. I just like having the plugs, wires don't get crossed later and less chance of them coming loose. But $35 is way too much to spend unless they aren't available in the yards.
 
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