fuel injection on an 81, hiding all the wiring and ecm?
 

Hey everyone!

Ive started the planning stages of reviving my pops and my old 1981 F250 4x4. The truck served us countless years, is well worn, and deserving of a full restoration. while it served most of its working days either with a big block/4 speed combo or in its later working days with a hot rod small block/4 speed combo, its new life will be a lot less stressful, so it will be getting a rebuilt straight six/ 5 speed combo. Pops is referring to it as his "retirement truck", it will be the truck he hops in to go run errands and drink coffee and maybe pull an occasional small trailer or haul a small load, but nothing overly strenuous.

With that idea in mind, I decided that I would be best if we outfitted the truck with things like fuel injection and air conditioning. I know that a few people have run fuel injection on this series of truck before, so I am looking for a little advice on fitment.

I pulled the entire dash harness, underhood harness, and chassis harness from the donor truck that also sourced the 300 six, so everything should work well together in that respect. my biggest concerns and questions are where does everyone stash the ECM? do you just lose the drivers kick panel vent and put it where the newer trucks put it? do you stash it somewhere else? does it need to be inside the cab, or can it live outside under the hood?

any other tips on doing this conversion will be greatly appreciated.

First question is the donor truck the same truck the 300/six came from and I am guessing it is EFI?


Being the ECM was inside (read cool) I don't think it would live long under the hood(read hot and sometimes wet) so I would keep it inside.


Now you may need to cut and shorten or make longer some of the EFI wires I don't know what this will do to the reading the ECM gets are the resistance changes and can throw the ECM in to a tizzy.


You did not did not say what year this donor is but maybe ditch the EFI from the donor and go with an aftermarket set up that say bolts to an aftermarket v4 intake.
This way you have support when it does not run right and think the ECM can be mounted anywhere but check first.


On trucks with AC the kick panel vents are not used and blocked off with a metal plate. Look at your donor if it has AC to see what I am talking about.
The kick panel covers are different as the non-AC trucks have doors to close off the vents when not used.


Also know if the parts truck has the AC it will not "bolt in" to a non-AC truck as the fire walls are different. I am told you can make it work by cutting the needed holes and covering the others.
Me I swapped the fire walls but I do not recommend doing this for everyone as it is work and takes skill to look stock.


Keep us posted on this.
Dave ----

I would mount the ECM in the exact same spot(or close to it) as it was in the donor. Then all the wires are the correct length. When these trucks had factory A/C, they did not use the kickpanel vent, it had a cover over it.

Good for you going EFI.

Any 300 six with EFI will be post bullnose and there are some significant firewall changes that preclude simply installing the later wiring. ECM location and the main harness firewall connector are the main considerations. You could copy the later trucks and modify the firewall to accommodate, or you could go with something along the lines of the 85/86 5.0 EFI trucks and install the ECM under the dash. These trucks used the same dash wiring as the carbureted versions and mounted the ECM under the dash by the transmission hump. There was a secondary harness for the EFI that ran through the firewall behind the left cylinder head.

I suppose with some thought, time and effort, you could modify the V8 EFI harness from an 85/86 to work with the 300 six ECM and engine, or you could modify the later harness to work as a standalone and install the ECM in a location of your choice. I did a write up on this in the engine swap forum some time ago.

https://www.ford-trucks.com/forums/1423515-making-a-stand-alone-efi-harness-pics.html#post16901192

The ECM itself is not really suited to direct exposure to underhood conditions. Moisture would be my biggest concern and heat next on the list. Perhaps you could fashion a water resistant box for underhood installation, but this could potentially add to the clutter that seems to put people off of the EFI system. I personally did not like where Ford mounted the ECM on any of the 85 through 96 trucks. The 85/86 location makes a rat's nest of wiring in a tight location and the kick panel location in the 87 to 96 trucks is in the lowest part of the cab. Aesthetically OK, but not the best in a 4X4 when you are contemplating a deep water crossing. Perhaps some room could be found behind the glove box?

thank for all for the warm replies, I was worried that I may get scolded for doing such things like swapping series.

to answer some questions...

the donor truck was an 89, it is where the 300 came from. I kept every inch of wiring out of the truck, as well as the dash itself, all the interior pieces, the HVAC box, pedals, steering column, etc. Since the donor truck was a red interior truck, this idea did cross my mind....

81 cabs are EXTREMELY hard to find rust free in northeast iowa. I do have in my possession a 1995 cab that is pretty well rust free, but it is as close to a bare cab as you can get, no doors or front clip or anything of that sort. I did ponder using the 95 cab as my base to rebuild, and using an 81 front clip, proper doors, and that way the wiring harness and HVAC from the 89 donor truck would work well ( I have already been down the road, the 87-91 and 92-96 trucks share nearly identical firewalls). My biggest issue then would be to retrofit the 81 dash into the cab, and if worst things came to worst, I would run the 89 dash in it ( although I don't want to, because it may ruin the look )

as far as deep water crossings and severe off road duties, this truck has already paid its dues there, and will be closer to "nice daily driver/borderline show truck" than it will be " off road powerhouse/ old work truck"

Not at all. :)

Subscribing to learn. But, you might read up on the work that Bill/85lebaront2 did on Darth: https://www.ford-trucks.com/forums/1...n-86-f350.html If I remember correctly he used a later dash and I know he added EFI to the 460.

Gary, I joined this particular part of the forum during my building of Clyde and felt a bit inspired with your dad's truck build. I always told pops I was going to restore Red and white for him, so here I am.

Because you all decided to show such interest in this project, I decided to drum up a photo for you all. Here is the Red and White truck.

Attachment 288166

This was taken the day we brought him back home from the farm where he has been resting for close to a decade. Exact mileage is unknown, but it is north of 600,000. Pops and I are the 5th owners of the truck, it was originally a 300/4 speed truck, in the picture it is on engine #6, and transmission #3. it has had small blocks, big blocks, even a chevy 350 powering it before. The current setup in the picture is a 351W/4 speed.

the cab got new floors, rockers, and cab corners in 1996, along with a new front clip and fresh paint. you may notice the hood s a different shade of red, its because pops thought it would b e a good idea to put clear plastic line for fuel line on the 390 that was in it around 2000-ish, and it melted while I was driving, and lit on fire. The truck has been to over 20 states with pops and I driving, we have had it hanging on its side over a ravine before, it drove me to prom, it moved me to college, it didn't even slow down when we hit that deer, and we managed to break every rear leaf spring and blow up the 390 in the same day with it.

Pops always said, you cant tell the story unless you can point and say "and there's the truck."

If you decide to use the 89 dash, you will have to use 87-up fuel tanks.

That is quite a story! Glad to see that truck is being restored. :-X22

yup, I figured that I would need to run an 89 fuel tank regardless. I will be running a rear tank only, with no side saddle tank.

Well, I guess you know if you are going to run a 89 fuel tank, you will need to use a 85-86 sending unit with the older dash. Earlier than that and they won't fit the large hole in the 89 tank. For the same reason you have to use the later dash with the later tank, you need to use the earlier sending unit with the earlier dash.

Yeah, I didn't really think about that, that's a great tip!