Ford Reviving the family truck - 1985 F-250 Diesel Swap

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Mini-Truck Enthusiast
Jul 12, 2013
Tucson, Arizona
I know nobody ever looks here, but I figured I'd post up the story of my family's 1985 Ford F-250 anyway.

This truck has been in the family since 1987 when my dad bought it off of a company that used it to maintain phone lines. Since the mid 90's my dad kept it up in the White Mountains at the cabin to use as a farm truck. Here's what it looked like way back in 2013.


I've wanted the truck my whole life, and back in 2015 my mom was driving the truck into town and she got sick of how bad the steering was on it and told my dad he needed to get rid of it and get something newer. He ended up buying a 2003 F-150 and was going to send this thing to the junkyard. I told him that I wanted it and he ended up giving it to me as my 20th birthday present.

So my buddy and I drove my dad's F-250 all the way up to the White Mountains where we picked it up. It had been sitting at the Springerville airport for a while and it definitely took some time to get it started. After several sprays of starting fluid (and a small fire) we finally got it running.


I drove it back to the family farm and we enjoyed the next couple of days dirt biking, drinking beers and hanging out. On the last day of our trip we loaded it up onto the U-haul trailer and started driving back to Tucson.



We got back to Tucson and I drove it off the trailer and started driving it for a couple weeks. And then unfortunately, and regrettably the truck sat. Between going to school and not having any money to throw at it I never really drove it. It was driven maybe once every couple months for dump runs and work loads. But never really daily driven. I always had dreams to swap in a 7.3L powerstroke just like my dad's but never thought it was going to happen. I didn't have the know-how or the money to even try to do anything with it - hell I was still learning how to do basic car maintenance!

Fast forward to March this year and I finally decided it was time to get this ol' gal going and promote it to daily driver status. With some know how and some money to throw at it I started going through it. The thing would barely run and eventually died on me when I was trying to take it on a little test drive. The battery had died so I replaced that and then the truck ran for a little bit and then died again.

I smelled gas and noticed the carburetor was just spraying gas out of every gasket. So I pulled it into the garage and started working on it. Pulled the carburetor off and over a weekend rebuilt it. The truck started right up but I could never get it to run right after a while. I couldn’t quite figure it out and found out it was a bad fuel pump and it wasn’t getting gas consistently – and of course every time I pulled the fuel line off to check it the pump was working. Just my luck. So I rigged up my own fuel system and threw on an Edelbrock carb so I could go to my buddy’s house and rip the bed off because I really didn’t want to drop two full tanks of gas.




After we got the truck dialed in and I gave it a little tune up with new plugs, wires, oil & an ignition module, the truck was running fantastic. Started right up, idled beautifully, and honestly I had never seen it run so well. After my last test drive before I was about to attempt an excursion to my buddy’s, I noticed the oil pressure gauge inside the cab was really low. Not trusting the gauge I bought a mechanical oil pressure gauge and well, the oil pressure was a little bit on the low side and we had some really, really clattery heads.


Considering this was going to be my daily driver I wanted to know it was reliable so I started planning on rebuilding the motor. Given the truck’s history of neglect I figured it was time to start fresh. So I ordered the parts for the rebuild and started planning it when I found this truck on craigslist.




It was a 1986 F-350 with a 6.9L diesel, T19 manual transmission with a Dana 60 solid front axle. The truck was a single cab, long bed just like mine and only had 160k miles on it. It had everything I wanted. It was in Phoenix listed for $3000 so I texted the guy immediately and he got back to me and we started talking. He could tell I was interested and told me if I really wanted it he’d sell it for $2,500 since that’s what he had into it.

I drove up the next night and looked the truck over and well, you guessed it – bought the truck. Drove it back to Tucson on the freeway and absolutely loved the way it drove. Got back to town that night and decided it was time to live my dreams of making the old truck a diesel. It was time for a body swap.

More on that to come...
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Do you know what the original motor was? There is a turbo kit for the 6.9 IDI that is available from banks that'll wake up the 6.9, the only problem is you have to keep boost low as the 6.9 has 21 or 21.5:1 compression ratio.
Do you know what the original motor was? There is a turbo kit for the 6.9 IDI that is available from banks that'll wake up the 6.9, the only problem is you have to keep boost low as the 6.9 has 21 or 21.5:1 compression ratio.

The original motor in my old Ford? It was a 7.5L V8. The motor in the brown truck always was the 6.9 IDI.

Personally I have no interest in turboing it at this point in time, but once I use it to get to the higher elevations I'll be keeping my eye on the exhaust. If it's really struggling I'll probably look into it at that point.
Now that I got the 86, it was time to start getting to work. On Saturday I had my old 85 towed over to my buddy's house where we would be doing the swap.



I drove the 86 over there and we started cleaning up and making room for the swap. First thing we wanted to do was build a little cart to move the beds around the shop if we needed to. So we took some old wrought iron he had lying around and welded up this cool little thing.


Now with our new tool, it was time to test it out and get the bed onto it. The 86 was the first to go under the knife. So we disconnected the bed bolts and all the wires and filler necks and then hoisted the bed up in the air with some ratchet straps. Then we pulled the truck out and lowered the bed onto our new cart.


And that new cart worked pretty well!

So once the bed was pulled we started disconnecting all the wires in the engine bay. From there we started to take off the front fenders and the headlight surrounds. I know most people would've pulled the whole doghouse with the core support, but the core supports on the gas and diesel trucks are different and it was just easier to leave the core supports in place on both the trucks. Also makes for a lot less coolant spilled too! Ziploc bags and sharpies are your best friends for keeping the million screws and bolts from the front end together.

With the front fenders off, we had to start getting ready to lift the cab. To do this was pretty easy. Disconnect the hood latch from the core support, the speedo cable from the transfer case and the emergency brake from underneath the frame. You also need to take off the clutch master cylinder, the brake master cylinder, everything that was on the fenders and disconnect the heater hoses. From there you can take out the shifters, but be careful! There is a little rollpin that goes in the base of the T19/T18 where the shifter sits. Just make sure you put the truck in neutral when you pull it out and do it slowly. The transfer case shifter simply unbolts with two 1/2" bolts.

From there it's just a matter of unbolting the cab bolts (2 under the front carpet, 2 in the rear behind bench seat) and lifting the cab.

And by 7:30 that evening, we had liftoff!



And to think we did all of this in a days work! This wraps up the first day. I went home exhausted but ready to do it all over again the next day.
So now time to do the same thing all over again. We pulled the old farm truck into the stall next to it's new chassis. Man the one ton sits a lot higher!

And just like the day before, we started taking it apart. So first off comes the bed...


Then the fenders and finally - we got the cab off!


And rolled the chassis out of the frame. It's always so much easier doing this a seocnd time. We shaved a couple hours off of how long it took us the first time, even with the old girl fighting back a little bit.


Once we got the cab off, we lowered it onto some tires so we could start doing some body work. A lot of fender support pieces had broken off and the main fender support for the left side fender was literally dangling by a quarter inch of steel. No wonder it looked like it was going to fall off any time.


Here's our nice little pile of parts.


So to sum it up, in two days we had the trucks completely dissembled and ready for the swap. If we hadn't had to to body work on my old cab it probably would've been sitting on the diesel frame that night. But that's alright - we were looking forward to getting a break for a couple days.
After putting the truck on hiatus for a couple days, it was time to get back to work. With the 3 day memorial weekend ahead of us we were ready to grind and get this thing done.

I went over to his house on Friday and started slowly but surely re-welding the upper fender mount. It was torn and twisted in so many places we took our time building up the metal with weld and strengthening it. I did most of the welding myself, and as a newbie it was definitely a fun process.

The cab was in bad shape and had been previously welded on before. Everything that we re-welded had been touched by a welder who didn't know what they were doing and all the welds broke. We ended up building a gusset plate for the fender mount and then re-welded three other pieces of the cab back on. Mainly the two that hold the fender on with a bolt through that you have to get at by looking through the door. I don't have any pictures of this process because I was welding but it was definitely a good time.

Now with the cab all done, it was time for what I've been waiting for - to throw it onto the diesel frame. We jacked the cab back in the air and slid the diesel frame under it and slowly started lowering it..


Got it on the frame and got the cab bolts started. We left them loose in case we needed to adjust the cab when putting it back together, but finally!! The marriage is complete. But we still had quite a bit more work ahead of us.



Now with the cab on the frame it was time to tackle the wiring. I searched forever on these forums and contacted many members about the wiring differences between the diesel and the gas trucks. (Thanks @farmert on FTE) We were originally going to use my original harness and splice the diesel stuff in, but after some thought it was easier to just swap the entire harnesses.

So we pulled the dashes out of both trucks.


I noticed that the brown truck had a nice shiny new heater core in it so I pulled it and swapped it into my truck since well, now was as good a time as any to do that. We then put the complete dashes side by side and started unplugging the wiring harnesses.



And then just simply installed the diesel harness onto the back of my dashboard like the factory and put it back in. We ended up using the entire gauge cluster from the diesel in my truck to keep things simpler, and I liked having the tach. With the diesel harness in my truck, everything was literally plug and play. I bolted on the front passenger fender so we could get the starter relay plugged in and a battery safely mounted. Now it was time to see if it would run.

So I turned the key, crossed my fingers, and heard the sweet sound of that 6.9 diesel. Here's some videos of it running with it's new heart for the first time.

Knowing that it was running and making sure that everything worked, it was now time to start piecing the truck back together. So I reinstalled both fenders as my buddy looked into fixing the glow plug system on the truck. They had never worked before so we ended up putting in a new relay and a manual momentary switch so I could bypass the relay and manually operate the glowplugs if needed.

And by the end of Sunday night, I had a running truck with both of it's fenders on! Man check out those body lines! The left side fender doesn't look like it's going to fall off any time soon! :-jammin



Now all that was left was to put her back together, but that was for the next day. We were worn out.
So now that my truck is up and running, it was time to start making it look like a truck again. So we started putting her all back together. Backed the truck under the bed and got the bed back on..



Then we had a couple things left to button up under the hood. The PO had made some ghetto battery tray and that wasn't going to work. So we fabricated a nice one out of some diamond plate we had lying around. Once we were done under the hood, all we had to do was put the hood back on..


And BAM! Just like that we had a complete truck again!



I started her up and took the gal for a test drive to make sure everything was working out. No major issues at all! Still had to get used to driving it but drove it home with a smile on my face the whole way.

It's crazy to think that we disassembled two trucks and put one back together in two weekends. Yes, they were really long weekends to say the least, but I'll be honest - this really wasn't that bad. I'd say the worst part of doing a swap like this is keeping track of your hardware and lifting the cab and bed.

This truck is really sentimental to me and the family, and it was so cool to see it go from this:



My parents were absolutely blown away and love the new truck. They're even thinking about selling their other diesel and just use this for towing!
Overall this was a really fun build and honestly one of my greatest achievements. Converting this truck to a diesel was always a dream of mine, and now I get to drive that dream and it's unbelievable.

Thanks for reading everyone! I'll keep posting updates on what I got to do her down the road.
Man, foo, you better do a sick ass write up about the fabbed diamond plate battery tray. This thread is too good to be too short, ese.

Haha I love the way you write mang. (or foo?)

No crazy writeup on it, it wasn't too bad! Just a lot of measuring, cutting and bending of the diamond plate. I'll try to get some pics of it tomorrow when I do some more work on it!
Well done young man!

I had an 84 F250 4WD with one ton suspension. Had the straight 6 and a 5 speed with granny gear. Loved that truck, bought it new and drove it for 9 years.
Well done young man!

I had an 84 F250 4WD with one ton suspension. Had the straight 6 and a 5 speed with granny gear. Loved that truck, bought it new and drove it for 9 years.

Thank you for the kind words Stan!! Your body dolly was the idea behind our bed dolly, sure works great!

And a F-250 with a straight 6 and one ton suspension? Whoooie that sounds like a BA truck! Pretty rare to see any F-250's with the old 300 I6 anymore!
Very nice job and write up. You may want the turbo later.
Very nice job and write up. You may want the turbo later.

Thank you! It was a really fun ride. I'm pretty sure the truck will get a turbo added at some point in it's life, but it's pretty low on the priority list right now!
Since I've gotten it done, this truck has definitely kept me busy! The first weekend after getting the truck going I decided I wanted to fix the old spare tire carrier in the bed. So I glued it back together with my Millermatic 211. I also had to make a bracket to hold the tire in place since the original one is long gone. It's not pretty, but it's simple and functional and does it's job.



Now being that it is 110 degrees in Arizona right now, I really needed to get the A/C going. I turned the compressor by hand and it had some friction so it seemed fine. Everything in the system looked clean and there was nothing to show that the A/C didn't work or leaked. So I flushed out the lines, replaced the drier and the orifice tube, converted it to R134A, charged it up...and it worked! Nice cold A/C. The fan resistor is out so it only works on high, but that's good with me. It was nice to have that done. While we were working on charging the A/ I found that the lift pump was leaking from the diaphragm inside which gave me a new project to do.

I ordered the new pump and decided to do the vacuum pump while I was in there since you have to take it off anyway. The brake pedal was stiff and the booster on my truck worked before the swap, and after verifying there were no leaks I knew it was time to replace it. So I spent the weekend replacing the lift pump, the vacuum pump and I put in a new fuel filter since I had to bleed the system anyway.



The truck has been my DD, and I was getting sick of listening to the one AM channel that worked on the original radio. I had an old Pioneer lying around that I got from the brown truck and installed it. The Metra dash kit worked okay, but I was really impressed by their plug adapters. It was literally plug and play and the radio works well. I used some black electrical tape around the edges of it so the silver din mount wouldn't show. (thanks ctubutis for the idea) It looks pretty good to me!


I'm extremely happy with the truck and am even happier to cross projects off my list. I only have a few big ones left, and then I should be done with the truck for a little bit other than maintenance. (hopefully

I've been tinkering a little bit on the truck the past couple of weeks.

I went ahead and installed some "nice" manual mechanical temp and oil pressure gauges. Unfortunately I'm going to have to redo it because it looks like my -4AN line that I've used has sprung a leak somehow?
I'm just going to switch to copper and call it a day...the temp gauge works pretty well at least!


I also redesigned my spare tire holder. The old one worked pretty well but it just looked really tacky...I know I said I didn't care about how it looked but I figured it should look HALFWAY decent. So I modified it a little bit and put in another bolt to make it a little bit more robust. And then I painted it! Looks alright to me.



I also had to install a new battery, since my other one was toast. Luckily I was able to get it warrantied out so no money there. However even after that the truck kept dying on me, and being a big old diesel it was impossible to jump it! I tested the alternator and it failed immediately.

Unfortunately trying to find an alternator for this thing was a total PITA. O’Reilly’s had one but it only had a serpentine belt pulley on it. Autozone had one that in the picture HAD the two pulley v-belt but in person only had one. So I STILL had to swap pulleys. Not a big deal. The actual alternator replacement only took about 10 minutes though…love the fact it’s right there on top of the motor.

I was also having an issue with my parking lights not shutting off even when the headlights were off. A new headlight switch fixed that.

So far so good though – she’s running like a top and extremely comfortable to drive. I’m going to replumb that oil pressure gauge and then it’ll be time to start working on cosmetics – new vinyl floor and a new dash pad.

More to come!
Be careful with copper on an oil line. They have been known to fatigue and crack from vibration.
Be careful with copper on an oil line. They have been known to fatigue and crack from vibration.

Thanks for the heads up! I will be putting in some coils to help with the vibrations after the sender and before it goes in through the firewall. That's always worked for me in the past.

I tried to do it right with stainless steel but spent so much damn money in adapters and line just to have it leak I'm just over it!

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