6.5L Turbo Diesel Jeep YJ

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6.5L Turbo Diesel Jeep YJ

By Jim Fleming, Member #1600

I built this 1989 YJ Jeep back in 1990. It has an A.J.'s fiberglass body with a one piece front clip. I am currently running the 1996 6.5L turbo diesel (military HUMVEE) backed by a 700R4 and a NP207 transfer case. I have almost too much power (never thought I would ever say that). I am still running the stock YJ axles (Dana 35 rear and Dana 30 front), but have a Dana 44 that will replace the front axle and a Dana 60 to replace the rear. I also have a NP205 transfer case to put in this summer. All this rolls on 35" BFGoodrich AT tires.

In 1993 I had a 6.2L NA in it, but one day while on the freeway it started popping and missing. I drove it home (about 75 miles) and checked the oil. It was overfull. I didn't know what was wrong (The Diesel Page wasn't "on the air" back then), so I pulled the 6.2 and installed a 4.3L gasser. I later found out that the 6.2 had a broken rocker arm.

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After a few years with the 4.3 and later a 305 gas engine, I decided to go back to a diesel (12-15 mpg and no improvement in power over the diesel). I lucked out and found a guy here in Michigan who was selling surplus 6.5L engines out of HUMVEE's. These were complete engines minus only the accessories. The best part was that they were available at core prices. I took my tools with me and made sure the engine would at least turn over, then bought 2 of them. One looked like it had never been run (the exhaust manifolds were still painted black). The other one had about 2 lbs of sand and dirt packed in the center by the turbo. When I got them home I installed the used engine in the Jeep and tried to fire it up, but couldn't get fuel to the injectors. I took the injection pump off of the engine and took it to my mechanic. He immediately knew what was wrong. He simply changed the 24 volt fuel shut-off solenoid to one rated at 12 volts. The engine fired right up after getting the correct solenoid installed.

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The only major problem that I had installing this engine in the Jeep was getting enough turbo clearance. Since the HUMVEE turbos are mounted at the rear of the engine valley, I had to lower the engine in the frame and bring it forward a bit to provide adequate firewall clearance. Moving the engine forward left no room for an engine driven fan, so I installed an electric pusher fan along with the new aluminum radiator. The only time engine heat becomes a problem is while idling in traffic for extended periods of time. I am using one high-capacity battery and a manual glow plug controller. I am also running a straight pipe with no muffler.

Since installing the 6.5, I have put close to 10,000 miles on the Jeep and have gotten between 18-20 mpg. As far as I am concerned, this is the best engine for my situation. A 350 gas engine could be installed that has as much power, but it would never get 18 mpg.

Jim Fleming
TDP Member #1600

www.TheDieselPage.com

You pretty much have my dream jeep. I'd love to do a Jeep Wrangler Diesel conversion. One day I will...

Real Nice looking Jeep. You are defeinetly right in that I doubt a 350 would get 18 mpg. More like 8 mpg if you are lucky...

When you started to convert your jeep, what was the stock engine and tranny in it? And how much did you have to change after converting to a 6.5 diesel in your YJ? It's def pretty sick, I must say.

I have compiled some info from the web, which took me a considerable abount of time because from what I've read, most people are afraid of diesels. A couple of things that will be helpful putting a 6.2L diesel in a Jeep YJ is the Advanced Adapters Chevy 350 conversion kit. I don't know the part number, but it will work. The only difference is that you have to add a 1/8th steel spacer between the motor mount and engine. A real plus to using the 6.2 is that is has the same bolt pattern as the 350. Makes transmission choices way more variable.

I have question for you.

how is the noise inside??

I am installing a 6.2 in my YJ project right now, and was wondering about the noise level. ( I am hoping it works well)

The noise isn't any worse than a regular V-8 with headers and an aggresive exhaust. You can Line-X the tub of your Jeep or use Dynamat for sound deadening. It all depends on the type of exhaust you choose to run. If you want to run 4" staight pipes you can obviously expect some resonation inside and most likey some hearing damage, but it would sound cool. Before I started my swap, I talked to a diesel shop locally about using headers. They said for what I'm using the engine for it wouldn't be worth the expense. They said the manifolds would be fine with minimal or no exhaust crowding preventing good flow. Also, i have gotten my manifolds Jetthott coated. It was reasonable, right around $260.00.

My Jeep: 1980 Cj7 had an AMC 258 Straight 6
The donor: 1984 C20 with a 6.2L and a TH400
Motor mounts “Novak Conversions” part #MMX-NC1

A Few Questions for you that have completed your project


What changes did you make to the front suspension for the added weight?

Did you have any issues with clearance in the engine bay?

I plan on Running electric fans and an aluminum radiator did anyone consider a hi-flow water pump? Or is the stock one good enough?

Thanks :cool:

For my situation, my jeep will get a 4" lift springover. Ask whomever you talk to when you buy your lift if it will hold up to a heavy V-8 conversion. You have to add some lift to clear the oil pan. I am going to use an aluminum radiator, but there is going to some math involved. Instead of having an entire chevy truck front end to play with width wise, you're going to be down to half the space. I'm going to make mine identical to the stock, but deeper. at least a four core set up. If you get the right amount of radiator, I wouldn't think you would have to go with a high flow pump, but that is more personal preference. Electric fans are a must. Engine driven fans are a dinosaur idea that has had it's time. Why waste gas on them? A nice thing that I have been finding out is that the advance adapter Chevy 350 motor mount conversion kit works with the 6.2L. Depending on what you plan on for a drive train, will tell you how much engine bay clearance front to back you'll have. There is plenty of room. Go slow, and make sure you get a radiator and some fans to mock up with your motor with all the accessories. finding out that you blew $400 on a custom radiator that you can't use blows big time.

I know this an old thread but I'm thinking about doing this swap in my 89 YJ. It currently has the carbureted 4.2l inline 6. Also my first jeep. Can I still use the factory gas tank and sending unit? What else should I consider before doing this swap? Thanks