Magnum and Wiring Swap

[tcanin00]

I had started a long and all over the place thread that can be found here: Six years should be long enough...
There are three different cars involved in this process. The first was a 1970 Dart Swinger that was too rusty to repair, so it became a parts car to a stripped down shell. Some questionable body work had bone, and both the front and rear inner fenders had been cut and weakened the car. I decided to cut my losses and try to find a complete car that was worth having.
I found a '71 Dart Swinger in the middle of Ohio last year. I was worried that a bad paint job was hiding something, but the car looked better in person and is solid.

It had a 318 with a Weiand intake, Holley 600 vacuum secondary, and long tube headers. It idled like it had a rowdy cam, but it wouldn't rev.
Short story long, I got it running decent and drove it for a couple of months before pulling that 318 to get ready for the Magnum 318.

I was originally going to use an engine and transmission from a 1992 B-250 van, but I found a deal on a 1994 Dakota that had a Hughes dual plane intake and a Comp Cam.

I also took the complete harness from the truck so I could add cruise control, intermittent wipers, and rear wheel anti lock brakes to my car.

So the process of eliminating what isn't necessary from the Dakota's harness and tying it into the Dart's begins.

 

[tcanin00]

The engine went in with a fight, mostly because of the long tube headers. I put the carb on it so i could test run it in the Dart and pull it into the garage.

The first problem was clearance between the dust shield and the Magnum flex plate.

I'm using the Dart's 904 transmission. Before putting the engine in I notched the bellhousing for the Magnum crank position sensor.
First was to route the rear harness to power the fuel pump. I had replaced the gas tank with a Tanks Inc. one that can support an efi set up.

Then onto removing the Dart's harness and replacing it.

Started putting all the efi system back on the engine. I also converted my car to manual steering and eliminated the power steering pump.

This is the belt I used.

 

[tcanin00]

I like wiring, as long as I have schematics and time. Also have the harness out of the car helps.

What was removed from the Dakota's harness. It had power windows and mirrors and I didn't need the extra wires and connectors.

The main thing I wanted to accomplish was keeping the interior as stock looking as possible. That meant wiring the Dart's switches and connectors into the harness.

I also had to use the B250's fuse and flasher blocks. The Dakota's fuse block is much bigger and wouldn't fit where I wanted it.

Some time and harness tape later, I had this. Pretty much a plug and play harness for my Dart. Before taping it up for good, it tested it to make sure everything worked the way it should. I found a problem with how the original foot operated high beam switch was wired and fixed it before moving on.

The "new" harness going in. Also something I forgot to mention, the Dakota's firewall connection is almost the same size as the Dart's. I might look into using the Dart's connector to secure it in place better. Right now it's held in place by the center bolt. Sounds like a "not right now" problem.

 

[tcanin00]

The result of hours of tracing schematics, soldering, and taping:


What I'm trying to figure out now is the missing when it's given constant throttle. Any advice would be appreciated.

 

[tcanin00]

In another thread about test running the engine here: Attempt at test running a Magnum
I was given great advice by knowledgeable guys on this forum. One thing that was recommended was mechanically zero the timing. I went through that procedure and haven't moved the distributor since. I'll put a timing light on it to see where it is. I know moving distributor on this engine is not the same as on a regular engine since it picks up the crank position signal from the flywheel. I'm thinking the rotor might be out of phase with the cap.

 

[TT5.9mag]

It’s called “fuel sync” on the magnum and needs to be set with a scan tool. I don’t necessarily think that’s the revving problem. But get it right so you can eliminate it as a possibility.

 

[tcanin00]

I remember hearing about how important it is that the fuel sync is set. I need to get or borrow a scan tool to adjust it.

 

[rbkt65]

try this mopar tsb. it should also work on the 94 engine. 18-16-92 rev a. it sets the sync also, so you don't have to have a scan tool.

 

[JDMopar]

You may or may not have seen this sync video, but thought I'd drop it in here for you so you don't have to hunt it. Hope it helps. Good job on the harness! I'm going to put a low mile 1998 5.9 Magnum into my 88 D100, so I gotta figure all that out too. I have the complete wiring, computer and fuse box from under the hood of the 98 truck.

 

[tcanin00]

You may or may not have seen this sync video, but thought I'd drop it in here for you so you don't have to hunt it. Hope it helps. Good job on the harness! I'm going to put a low mile 1998 5.9 Magnum into my 88 D100, so I gotta figure all that out too. I have the complete wiring, computer and fuse box from under the hood of the 98 truck.

Thanks for posting this video. He really explains the process well. Someone posted it in another thread an it's how I set the engine to mechanical zero.
Thanks, the harness was time consuming. I worked on it when I had time. It took about two months a few hours at a time. Having good schematics and a complete harness helps. I had read that the Ram's ground the headlights back at the headlight switch. Check your schematics and confirm. I ran into some weirdness with wiring in the original foot operated high beam switch into the high beam selector from the multifunction switch. The Dakota's selector wire keeps the switch 12V/hot at all times for the flash function. With it going to the foot switch, it made the headlights stay n regardless of headlight switch or high beam position. I removed that wire and picked up the high beam indicator source from the high beam output wire.

 

[tcanin00]

try this mopar tsb. it should also work on the 94 engine. 18-16-92 rev a. it sets the sync also, so you don't have to have a scan tool.

Thank you, rbkt65. I'll check it out and let you know if it works.

 

[tcanin00]

Up until yesterday, I had not driven the car. I got it together enough for a test drive. Initially it fumbled and misfired going up a hill and I thought I was going to bring it back to the house. But it cleared up and started running better. Good enough to drive around some more.
It has a hard time going from idle to about 1,500 RPM. Almost like it surges up and down before getting past it. It does have a Comp Cams Xtreme Energy .484 backed to a stock 904 and convertor. I wouldn't think that would be too much cam a stock convertor.
Also when I put a timing light on it, the timing fluctuates 5-10* at idle. I thought that was odd. It has a new timing chain and the distributor hold down bolt is tight.

 

[JDMopar]

Thanks for the tip about the lights! My plan is, to just use the Magnum under hood wiring harness for engine management only and leave the rest of the lighting and stuff as is. My D100 is just an old beat around truck that I want to be more dependable and easy for my wife to use if needed. I could throw a carb and ignition on it to do away with the throttle body FI that sucks out loud and it would be fine for me, but it's been so long since she had something with a carb, she's forgotten how to get it to start...lol. She has the patience of a Honey Badger, so just fixing the truck is easier than explaining how a choke works!

 

[tcanin00]

No problem. Some of the other swaps I've read, they just used the engine harness and tied into the start circuit from their original wiring. I could have done that, but I prefer the hard way.

 

[408 swinger]

So, what is actually "needed" out of the donor harness to make the Magnum run? I would imagine it's a little different between obd 1 and obd 2? Following along, thanks for the info!!

 

[TT5.9mag]

So, what is actually "needed" out of the donor harness to make the Magnum run? I would imagine it's a little different between obd 1 and obd 2? Following along, thanks for the info!!

For obd2, if you use the original engine harness and PDC from the doner vehicle, all you need is power to the input of the PDC, an ignition hot and a ground. Then a start signal.

 

[tcanin00]

So, what is actually "needed" out of the donor harness to make the Magnum run? I would imagine it's a little different between obd 1 and obd 2? Following along, thanks for the info!!

To be honest, I don't know the minimal for an OBD I harness since I had an entire Dakota harness that I put in my car.
I would think it would be similar to the OBD II harness like TT5.9mag said, just battery voltage, switched ignition voltage, start signal, and a ground.
You can download FSM manuals for free and trace the schematics to see what the bare minimum is to make it work. I used the 1995 Dakota manual to eliminate what I didn't need from it's harness.

 

[tcanin00]

Also, the Mopar TSB 18-16-92 rev a made a difference. It idles smoother and runs better at low RPM. My commute to work is 3.8 miles roundtrip, so I haven't driven it much after "setting" the fuel sync. I'll drive it some more and see how it is.
I will say that this motor pulls much better than the 1988 roller cam 318 with 915 heads that was in it. Might just be my own justification. I think going from a poorly tuned Holley 600 to efi is where the biggest difference is being made, plus higher compression, better flowing heads, and a mild cam.

 

[DionR]

I will say that this motor pulls much better than the 1988 roller cam 318 with 915 heads that was in it. Might just be my own justification. I think going from a poorly tuned Holley 600 to efi is where the biggest difference is being made, plus higher compression, better flowing heads, and a mild cam.

I went from a 318 TBI to a 5.9 SMPI and for me the bottom end torque difference was night and day better. Even pulls a steeper hill in OD without kicking down now. Completely different rig.

 

[DionR]

I've got a copy of the instructions for the P5153590 kit for the 360 crate motors but can't get to it right now and can't find a link to post. It would be about the best overview of what needs to remain if you wanted to cut down a harness.

I know it will need an ASD relay and fuel pump relay as well and maybe a couple of fuses to keep things safe, if you didn't want to keep the OEM PDC.

 

[TT5.9mag]

So, what is actually "needed" out of the donor harness to make the Magnum run? I would imagine it's a little different between obd 1 and obd 2? Following along, thanks for the info!!

I did mine with a stock obd2 harness and PDC, it was fairly easy with a factory service manual. If you want really simple, joint the magnum swap group on Facebook, the Moderator makes swap harnesses for od1 and 2 and they are just the necessities.

 

[75slant6]

So, what is actually "needed" out of the donor harness to make the Magnum run? I would imagine it's a little different between obd 1 and obd 2? Following along, thanks for the info!!

Here’s a good, informative video as to the best donors as well as what all is needed and what can be removed.

 

[jos51700]

I've got a copy of the instructions for the P5153590 kit for the 360 crate motors but can't get to it right now and can't find a link to post. It would be about the best overview of what needs to remain if you wanted to cut down a harness.

I know it will need an ASD relay and fuel pump relay as well and maybe a couple of fuses to keep things safe, if you didn't want to keep the OEM PDC.

View attachment 1716252594

If you post it, I'd be indebted to you!

 

[tcanin00]

I went from a 318 TBI to a 5.9 SMPI and for me the bottom end torque difference was night and day better. Even pulls a steeper hill in OD without kicking down now. Completely different rig.

Yeah, it's a completely different car with this motor.

 

[TT5.9mag]

Yeah, it's a completely different car with this motor.

Now put turbos on it.