Re: 5.9 magnum in a 79 3/4 ton truck
[Re: moparmandc]
#2111585
07/17/16 08:21 AM
07/17/16 08:21 AM
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Joined: Dec 2014
Posts: 5,821 ohio
ruderunner
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master
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Posts: 5,821
ohio
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Do you plan to use the 99 computer and wiring? That's going to cause headaches.
The 99 systems will be looking for an auto trans and numerous emissions systems that the 79 doesnt have.
Angry white pureblood male
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Re: 5.9 magnum in a 79 3/4 ton truck
[Re: ruderunner]
#2112069
07/17/16 10:04 PM
07/17/16 10:04 PM
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Joined: Oct 2004
Posts: 214
moparmandc
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I plan on using the 99 wiring just because I already have the donor and it cost me little of nothing. I thought about trying to flash the computer as a manual transmission before I took it out of the donor just so its not looking for the auto transmission. I don't care if it sets codes for the EVAP system it shouldn't affect how it runs. Also I'm not completely sure if it even matters how it runs if it does not see a transmission other than if it is in gear or not possibly. I also am curious if it actually needs to see a speed sensor or not I don't think that the speed sensor would affect the fuel trim. I am not worried about having to pass any emissions testing or any of that. I actually have quite a bit of background working on these systems as I was a Chrysler tech for over 10 years til about 6 years ago. So I'm kinda trying to "dust" the cob webs off the brain here to remember what these trucks actually had to have to run right as far as the engine goes.
Last edited by moparmandc; 07/17/16 10:17 PM.
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Re: 5.9 magnum in a 79 3/4 ton truck
[Re: moparmandc]
#2112372
07/18/16 12:31 PM
07/18/16 12:31 PM
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Joined: Feb 2003
Posts: 21,318 Manitoba, Canada
DaytonaTurbo
Too Many Posts
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Manitoba, Canada
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I swapped a 99 5.2 magnum into my 80's jeep with manual trans. I too thought I was going to use the ECU/wiring out of the donor 99 dakota. Not a good idea. To get it to run, you will need to spend a couple hundred having the ECU flashed as an auto trans ECU will be looking for the transmission. Also it will be looking for the body control module. In addition, the 1996+ stuff is OBD-2 and the wiring in an ugly rats nest compared to the 92-95 stuff. For my swap, after digging through the 99 dakota wiring I eventually scrapped it and went to the junkyard. I found a 1995 Jeep Grand Cherokee with the 5.2 and I snagged the engine wiring harness and ECU. The 92-95 OBD-1 harness is so simple it's a thing of beauty. After peeling it apart, I found the engine control section of the harness is almost entirely self-contained. I only had to too 2 or 3 wires up to my original harness so supply power and ground to it. By far the easiest EFI swap I have ever done. I found the 99 engine sensors have different connectors, so I went back to the junkyard and snagged the sensors off the throttle body, distributor pickup and the 95 has an extra coolant sensor the 99 doesn't have. I had to drill and tap a small hole in the intake manifold for that one. I grabbed the fuel injectors off the 95 engine as well, as I read they had a slightly different flow rate. Also found out through trial and error that the Grand Cherokee ECU is looking for a security module(engine would fire for a second then die), so I snagged an ECU out of a manual trans Ram. Also I found out the hard way that the auto trans flywheel pickup sensor will not work with the manual transmission flywheel. The sensor is too long, and by bolting it down, then hitting the starter, the flywheel ground off the tip of the sensor. While shimming it may have worked, I just bought a manual trans sensor. Got her all buttoned up, hit the key and she fired up and purred like a brand new truck. Took her for a drive and found it was stalling on decel when rolling to a stop because I did not hook up the speed sensor. Did some hunting, found a speed sensor that would work with both my cable driven speedometer and the engine computer.
EDIT: FYI, I believe the OBD-2 computers pull timing if they don't see the auto transmission.
Last edited by DaytonaTurbo; 07/18/16 12:32 PM.
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Re: 5.9 magnum in a 79 3/4 ton truck
[Re: moparmandc]
#2114562
07/21/16 06:07 AM
07/21/16 06:07 AM
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Joined: Oct 2004
Posts: 214
moparmandc
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Ok so I have been away for a couple days and appreciate the input you guys have thrown out here for me. So far I haven't started on the swap itself yet. I bought a magnum flywheel today because I realized the balance difference from the LA and the tone ring issue so I think that is covered. Will I have to drill and tap holes for my clutch/pressure plate to work and if so is there a clutch/pressure plate that I should buy to avoid having to do that? I talked with the service manager who is a buddy at the dealership I used to work for about flashing the PCM to a manual transmission so I shouldn't have to worry about the auto transmission part right? I will look into those speed sensors that are driven by the gear and have the cable on them. I will certainly take a close look at the crank sensor clearance. I am still willing to try the 99 harness and PCM surely it can be done. I'm always up for a good challenge and if it can't be done I will bite the bullet and hit the junkyard for a 95 and older donor I suppose. Thanks guys keep the advise commin.
Last edited by moparmandc; 07/21/16 06:08 AM.
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Re: 5.9 magnum in a 79 3/4 ton truck
[Re: moparmandc]
#2115431
07/22/16 12:17 PM
07/22/16 12:17 PM
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Joined: Feb 2003
Posts: 21,318 Manitoba, Canada
DaytonaTurbo
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Manitoba, Canada
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I talked with the service manager who is a buddy at the dealership I used to work for about flashing the PCM to a manual transmission so I shouldn't have to worry about the auto transmission part right?
I am still willing to try the 99 harness and PCM surely it can be done. I'm always up for a good challenge and if it can't be done I will bite the bullet and hit the junkyard for a 95 and older donor I suppose. Thanks guys keep the advise commin. If you have a buddy who can do the recalibration for free, you can give it a try. However, the way I understand it, the OEM calibration is also looking for the body control module to verify the key against the VIN. If you can have the ECU reflashed to eliminate the security as well, then you should be in business. While you can make the 99 harness work, once you start ripping into it, you may not want to. I'm good with wiring, have done several EFI swaps and decided it wasn't worth it. However that was also largely motivated by the fact that I didn't want to shell out 200 bucks to have the ECU recalibrated as I don't have any avenues to get that done for free. The ease of working with the OBD-1 stuff was worth it. Also, the OBD-1 engine harness has a wire that I ran to a light in the dash for the check engine. So I can cycle the key on-off-on-off-on and the light will flash codes back at me. With the 1996+ harness you will want to wire in the data link connector so you can hook an OBD2 code reader up to it. In addition, the OBD-2 can always be recalibrated later on for engine mods, where the OBD-1 system I did can't. For my application that was not an issue.
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Re: 5.9 magnum in a 79 3/4 ton truck
[Re: poorboy]
#2115598
07/22/16 03:56 PM
07/22/16 03:56 PM
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Joined: Feb 2003
Posts: 21,318 Manitoba, Canada
DaytonaTurbo
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Manitoba, Canada
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Don't you need the OBD-2 to use the port injection? Nope. 92-95 magnum engines were port injected OBD-1.
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Re: 5.9 magnum in a 79 3/4 ton truck
[Re: moparmandc]
#2116531
07/24/16 10:38 AM
07/24/16 10:38 AM
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Joined: Jan 2003
Posts: 5,791 Hamilton, Ontario Canada
Magnum
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master
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Posts: 5,791
Hamilton, Ontario Canada
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The factory fuel injection system is very complicated and not swap friendly. The simplest solution would be an aftermarket self learning and tunable system with a 4 barrel standard flange intake.
As for the flywheel. If you do not use the OEM system, you will not need the tone ring. Now you can physically bolt any combination to the crank and block. Just need to copy the 5.9L Magnum balance.
I had a local shop copy the imbalance of an B&M SFI auto trans driveplate. Then drill the same imbalance into a 318 neutral balance flywheel.
69 Super Bee, 93 Mustang LX, 04 Allure Super
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Re: 5.9 magnum in a 79 3/4 ton truck
[Re: poorboy]
#2117176
07/25/16 11:18 AM
07/25/16 11:18 AM
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Joined: Feb 2003
Posts: 21,318 Manitoba, Canada
DaytonaTurbo
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So, I can use my 90 OBD-1 computer to fire a port injection Magnum, or do I need the 92-95 computer? The 92-95 magnum port EFI computer and engine wiring harness is totally different than the old TBI system. While the 92-95 magnum system is the easiest to swap, and is OBD-1, nothing from your old TBI system will be able to be reused.
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