This is something ive kicked around for several years but there doesn't really seem to be a readily available candidate thats cost effective enough to bother with.The frame on a 3b isnt really all that strong and your options are mostly really heavy.
Jeep put
Perkins Diesel 4cyl diesels in
CJ5 's from around 1961-1969.They were expensive and didnt sell well but got about 30mpg.Speed wasn't a strong point but the 4cyl gassers of that era weren't exactly quick either.They were good engines but finding one would be hard and you wouldnt get anywhere quickly.
The renault turbo 4 they used in cherokees in '85-'86 is about the right size and economical but very rare and very unreliable.The nissan sd33 and sd33t[turbocharged] engines weigh as much as a bigblock chevy,arent very powerful or reliable or common and are too long for a '71 or older cj.The toyota 2lt 4cyl turbo diesel would be ideal size wise and give adequate power but they only sold a few in the US and canada in the mid/late '80s and are expensive because the toyota guys want them.
The 2.8 jeep put in libertys is good sizewise and powerwise but only came with auto
Transmission in the US and would be $$$$.The late model turbo 1.9 vw golf engine would be good in a
CJ3b but $$$$.Both are complicated wiring wise.
The 4bt cummins is a great engine but not a cheap swap.Check out 4btswaps.com for plenty of builds.
About the only fairly cheap, and available diesel swap ive come up with is the not very well liked 6.2 chevy.That would be too big to stick in a
CJ3b imho,but it doesnt weigh anymore than a sd33 scout engine,bolts up to sbc swap mounts and accepts any chevy
Transmission .I wouldnt want one in a tow rig but ive been quite happy with them in my '85 blazer and previous '83 suburban.You get 20-24 mpg in a blazer/suburban....unfortunately in a lighter
CJ7 /8 or yj you still only get 20 mpg......which is pretty close to what people get with late model fuel injected v6 and v8 gas swaps and less weight and much better performance.
In the end for me the diesel cj is an expensive novelty.You can buy a lot of gas for the cost of most diesel conversions,on a vehicle that most people will never drive enough to ever recoup the conversion costs.If you have the money and the 'cool factor' is worth it to you though....well go for it and goodluck....i like looking at rigs like that.If I fell into one of the few good donor possibilities real cheap I would still do it.It just seems most people are spending 5-10k on diesel swaps and I cant justify that.
