A guy wants to buy my 1990 7.3 and put it in his 1986 which came with the 6.9. My truck had the 4EOD, I think his has the 3-speed auto tranny that came bolted to the 6.9.

He is concerned about wiring. What wires/plugs/harness should I give him to make the swap easy?

Any other swap concerns for him?

Thanks,

Roy

 

the 7.3 is pretty much the same as the 6.9
he will not be able to use the overdrive trans unless he finds a computer for the trans.
the only electrical difference between the 6.9 and 7.3 is the glow plug controller.

 

Thanks TJC,

That is what I thought.

He will be using his 1986 transmission...not my OD transmission.

I don't think there are any sensors, or anything like that. Right?

Electrical on both the 6.9/7.3: charging, starting, glow plugs, FSS. And, that's it. Right?

Roy

 

He can use all of his accessories, alt, ps, etc. I think the glow plugs are different, yours will have the bullet connectors and his will have blade type. (Someone correct me if I'm wrong) you could include the wiring parts to for him to convert to the newer style glow plugs and controller.

 

that is what i would do, the 6.9 controllers are no where as good as the newer 7.3 glow plug controller.

 

The glow plugs and controller are going with the 7.3. I assume he'll use them. He did say his 6.9 plugs were on a toggle switch, so he might do that.

 

I don't think the C6 needs the TPS on the injection pump. My 1987 C6 equipped truck has the 460/7.5l

 

Include or add into the sale the wiring from the starter relay on the passenger side fender well, especially to the glow plug controller and 'Wait to Start' light (not sure what wire WTS light is but it probably has a plug before it goes through the firewall). If you include that relay and wires that go to the engine it will already be wired.

Either way, A couple of photos of your wiring, if the wiring is still intact would help him. Let him take the photos if he is nearby.

By the way, the C6 uses a Vacuum Regulator Valve (VRV) on the driver's side of the injection pump to control the shifting and if he hasn't pulled his engine yet I would remind him to remove that FIRST so it doesn't get damaged- I am assuming that he is going to use the injection pump on your 7.3 so he'll have to remove it anyway It does stick up high enough to get broken, (they're plastic) they are very difficult to find and essential for the C6. Looks like this:

 

The wiring harness that comes up from the front by the passenger side battery - some wires going to the starter relay may be different on yours, like containing a towing package wiring or accessories on your truck vs. his not having the same but I don't think that matters- he should use his own existing harness and connect it the same as in his existing truck.


If he can get images of the power distribution schematics for the 7.3L (they contain wire colors, plugs, etc. and compare those with the 6.9 He would have what he needs to be sure everything is right. I can probably help with the 6.9 wiring schematics from 1987 which ALSO has the 7.3 GP controller.

 

Super. Thanks guys.

I have sent the link to this thread to the prospective buyer,

Roy

 

What I wrote about the wiring harness was based on vague recollection- right after that I was doing other work under the hood today, looked at the wiring harness and it's not quite like I suggested. I think the 7.3 style Glow Plug harness probably will connect with the connector on his 86. I'm assuming the plug(connector) is the same but I might be mistaken. That would be one thing to check.

87-91 is the 8th generation and 80-86 is the 7th generation. I don't think there will be much if any difference in wire colors and the basic engine wiring unless it is the newer 7.3 style glow plug circuit.

I think i have converted all of the relevant schematics and diagrams (and many more) from screen shots of pages into .jpeg images for easy quick access so if your friend wants any of them he can send a private email through my profile and I'll send them directly and probably be able to help him figure out a few things because I've studied all of those schematics quite a few times to trace wiring see what components were in an enter circuit and how they worked with each other etc.

I'll also send the 'key' to what all of the symbols mean. I don't mean to make this sound complicated because I think what he is doing will be quite simple in terms of wiring I use the schematics to confirm that every wire is going to the right place.
Here, the main thing is probably just the glow plug controller circuit and glow plug harness (connects to the glow plugs)

I thought that sending the images privately might be more appropriate since I didn't recognize this topic as an engine swap project thread Also it would use less server space but I could post them here if it becomes a project thread.

If a discrepancy arises in an 87 schematic compared to what would be in an 86 schematic I could post it here and maybe someone could take a look at the same schematic for an 86 (7th generation) truck and identify the difference.

There were some significant design changes for 87 that possibly could affect some unrelated accessory wiring (if so, not much) but if he is using his truck's harness that won't matter.

When I looked at the wiring today it looks like putting a 1990 7.3 in a 1986 truck, in terms of wiring should be quite easy. I could also take a few pictures of the harness on my 6.9 since I'm working under the hood for the next two weeks and I have some clear access to get pictures.

There are likely some older topics in the forum covering this same job, putting a 7.3L IDI into a 6.9 truck, maybe a project topic which would be helpful and may already have answers to the main questions.

 

Thanks Fix,

I have a PDF of the complete Ford shop manuals. I have coverage of the '90 truck and all the IDI motors. I'll give him a copy of the whole lot. That should help, too.

Roy