Cummins in a MJ possible?? 3.3 or 3.9??

AM i crazy. I have seen this done on a yj Cummins sells a 3.3L 4 cly Diesel motor has a SAE4 bellhouseing pattern. It's actually made by Komatsu turbo and you can get it anywhere from 85 HP tp 110. Now i know it fits in a yj and looking at the mesurements i think it will fit. It's not too heavy around 500 pounds. Only problem it's around $4000. I can get and adpter to adapt a gm bellhousing/ clutch assembly to it then another adpter to go to an ax15. It's all mechanical so wiring will be minimal. i need to figure a fule system use stock tank mabey the pump also not shure on that. Anything else im missing?? they also make a 3.9 thats a cut down the of 5.9 but's it's 3 in longer and wither almost $250 more but I could get one alot cheaper possibly a used one and re sleve and freshern it up. Also has more power. Any thoughts on this am i nuts or does this seem feasable??? And i need to fab up ac and power steering brakets also some sort of vac pump to run hvac and brakes. Or can I use the engine because i thought a Turbo diesel cant be used to pull vacume but i might be wrong

Hmmm... Intersting...

First and foremost - you will not be able to use the stock fuel pump - it won't give you enough pressure for direct injection of Diesel fuel (which takes place right before compression peak.) The typical gasoline MPI pump gives something like 40psig or so, while Diesels need a few hundred psig. Also, you'll have to REALLY flush out the tank - mixing gasoline and Diesel ain't cool.

Check that YJ kit - if it includes a body lift, you're going to have some work to do. I seem to recall that Cummins Diesels are fairly "tall" engines, and that could be an issue. Remove the hood or fab up a really tall scoop, perhaps?

Vacuum pumps on Diesels are fairly common (I've seen them on Cat 3208's all the time,) which gives you an option. You could also convert your brakes over to Hydroboost (using P/S pump pressure to run brakes as well,) but you'll still want some sort of small vacuum pump - electrically- or engine-driven - to drive your HVAC controls. Going Diesel eliminates using the manifold for vacuum - Diesels don't have throttle plates (the accelerator regulates fuel delivery, not air delivery.)

You might also have an easier time getting a transmission to fit the engine directly, and then fabbing up mounts for that - rather than fabbing up adapters for the AX-whatever. Besides, what's nominal input torque maximum for the AX-series gearboxes? Diesels are typically low horsepower, but they've got torque in spades! This is important in selecting a transmission...

Lastly, if I may be so bold - try formatting your writing a bit better. I'd like to help, but the more effort I have to put into deciphering a post, the less I'm willing to put into answering it. Read your post, and then read mine - and tell me which is easier. Take a few moments to review your post before you hit "Commit" and make any changes that present themselves. No-one will think less of you if you take an extra moment or two to formulate your thoughts compleatly, but they damn sure will if they can't read what you write!

Considering the XJ was originally designed for the Renault 126TD (as well as the AMC150 and GM173,) I'm inclined to think that minimal reinforcement would be actually necessary, but I'd like to compare specs on the two engines before I commit to anything in public. Also, SBChevvy swaps are quite possible, and I've heard of a few BBChevvy swaps here - so whatever work needs doing can probably be done...

5-90

Ok Fuel Issue What do i need to do put an external pump becaue finding a internal pump to deliver those pressures will be difficult.

Second height your right they are very tall and somewhat wide for a inline engine but a cowl hood should work the one i saw in a yj did not have a body lift but it was a close fit to the hood.

Im not shure about the tourqe spec on the ax15 the one i saw yj was running one and he said it was ok, An aw4 is an option but a tps would have to be set up for the shift points.

I'd have to look up the "SAE4" bell bolt pattern, but something makes me want to think it just might correspond to SBChevvy - perhaps bolt a Muncie to the back of the engine? I seem to remember those "Rock Crusher" four-speed top-loaders being damn near indestructible, and I think it would give you better gear ratios. Either that, or perhaps a NV4500 (since you're going to be doing a fair bit of fab work anyhow...)

As far as the fuel pump, I don't see any reason why you couldn't adapt an existing application (say, International DT466, just for the sake of argument) to work with what you've got. If it's internal, you can fab something up to use the OEM "stinger." If it's external, just fab a pickup tube and bolt the pump to a frame rail or somesuch. I've also seen "two stage" pump setups on Diesels - a rear pump that delivers high volume at low pressure, and a forward pump that "boosts" the pressure to something the injection setup can use. That would involve two return lines (one return for the HP supply, and one for the HV supply,) but I'd think it would be doable.

Now you've got me thinking...

5-90

Just a note on using the stock pump. A diesel engine has its own fuel pump on it in my experience...including the cummins 5.9. The pump in the tank will only be a booster pump to get the fuel to the motor.

I don't see why the stock pump wouldn't work, As long as it supplies the high pressure pump with enough volume?

Cummins put alot of the 3.9 motors in chevy and ford devivery vans like the sunbeam bread ones. Im going to start looking around for a used one the rebuild kit is only about $400 for new sleeves pistons and seals assuming the bottom end and heads/valves area ok

OH..you seem to have covered that.

Carry on...

BTW... I would probably choose a four cylinder Izusu if I were gonna do it. 225 HP. Fairly compact as well, because they were designed to fit under a cab on those small flatbed trucks. However, they are fairly wide and maybe heavy (don't know).

Yeah I have be careful of weight and length because I want to avoid cutting the firewall.

The Cummins 4bt you are referring to uses a block mounted mechanical fuel pump driven off the cam, called a lift pump, this pump then feeds the high pressure injection pump so all you need to do is remove the factory in tank pump so that it just sucks from the bottom of the tank, but don't just disconnect the wires because it with cause to much restriction if you just leave it in the tank and suck though it. Also it may be easier to get an old bread truck and use the entire engine and tranny as some of these came with t-19's and some came with th350's or th400's and then adapt it the np231. oh and a small amount of gas in diesel is ok, it is similar to mixing acetone in with gas just try to get as much gas out as possible.

ExNews4XJ has some good info there. The bread truck motors were designed to replace the small block 350s originally placed in those trucks, and are in fact nearly a bolt-in swap from a 350 to the 3.9 diesel. Those trucks are pretty hard to find though unless you know a place that auctions/sells commercial surplus and used vehicles; they tend to be bought up quickly.

I recently finished a 5.9 cummins swap into a Ford Bronco. Sparing a lot of the technical details, one of the mods we did was to remove the in-tank fuel pump and plumb the tank directly to the input on the fuel primer of the Cummins, and this worked great. Definitely hook up the return fuel line if you do this - the Cummins pump has a fuel heater after it to reduce gelling, and they purposely send excess fuel back to the tank after it goes through this to help heat the rest of the fuel supply.

Aside from that, the 5.9 (and 3.9) motors are purely mechanical. At least before they went to the 24v versions. We had the motor installed and driving with just two wires: one to open the fuel valve solenoid (consider this the same wire that activates your ignition coil) and one to hit the starter solenoid. The mechanical controls on the motor take it from there. We were able to wire up all the factory Ford gauges in the Bronc to the Cummins unit as well - oil pressure we cut and spliced because the sending range was the same, engine temp we used an NPT adapter fitting to fit the Ford sender, and we got a tach signal by remounting the Ford tach sensor and grinding additional notches into the Cummins harmonic balancer. If you modify the tank properly you can keep the fuel level sender fully functional. We even used a standalone "computer" from a '90 CTD Dodge pickup to use the intake manifold temperature to properly trigger the intake grid heaters - which used the Ford factory 'wait to start' lamp. This same module also gets input from the 'water in fuel' sensor and activates the factory lamp. Pretty pimp to see the whole thing work from in-cab.

The power steering pump on the Cummins motors (which is usually an OEM unit adapted to the Cummins geartrain) bolted right up to the Ford/saginaw power steering box, so that's a non issue.

Alternator...we ended up using a heavy-duty adjustable unit from a school bus. The alternator on the Cummins motor was regulated by the Dodge computer, so if you're lucky enough to score a Chevy-based bread truck motor, you may get an internally regulated alternator.

We used the factory vacuum pump on the Cummins motor, and t'd it into the vent control lines and brake booster line. All accessories work fine.

Not sure how much of this helps you, but feel free to reply/contact me if you want any more info about Cummins swap stuff. Here's a pic of how it ended up...pretty clean IMO. Used the Dodge radiator and intercooler too.



I'd love to see someone on here put one in an MJ.

vetteboy said:

ExNews4XJ has some good info there. The bread truck motors were designed to replace the small block 350s originally placed in those trucks, and are in fact nearly a bolt-in swap from a 350 to the 3.9 diesel. Those trucks are pretty hard to find though unless you know a place that auctions/sells commercial surplus and used vehicles; they tend to be bought up quickly.

I recently finished a 5.9 cummins swap into a Ford Bronco. Sparing a lot of the technical details, one of the mods we did was to remove the in-tank fuel pump and plumb the tank directly to the input on the fuel primer of the Cummins, and this worked great. Definitely hook up the return fuel line if you do this - the Cummins pump has a fuel heater after it to reduce gelling, and they purposely send excess fuel back to the tank after it goes through this to help heat the rest of the fuel supply.

Aside from that, the 5.9 (and 3.9) motors are purely mechanical. At least before they went to the 24v versions. We had the motor installed and driving with just two wires: one to open the fuel valve solenoid (consider this the same wire that activates your ignition coil) and one to hit the starter solenoid. The mechanical controls on the motor take it from there. We were able to wire up all the factory Ford gauges in the Bronc to the Cummins unit as well - oil pressure we cut and spliced because the sending range was the same, engine temp we used an NPT adapter fitting to fit the Ford sender, and we got a tach signal by remounting the Ford tach sensor and grinding additional notches into the Cummins harmonic balancer. If you modify the tank properly you can keep the fuel level sender fully functional. We even used a standalone "computer" from a '90 CTD Dodge pickup to use the intake manifold temperature to properly trigger the intake grid heaters - which used the Ford factory 'wait to start' lamp. This same module also gets input from the 'water in fuel' sensor and activates the factory lamp. Pretty pimp to see the whole thing work from in-cab.

The power steering pump on the Cummins motors (which is usually an OEM unit adapted to the Cummins geartrain) bolted right up to the Ford/saginaw power steering box, so that's a non issue.

Alternator...we ended up using a heavy-duty adjustable unit from a school bus. The alternator on the Cummins motor was regulated by the Dodge computer, so if you're lucky enough to score a Chevy-based bread truck motor, you may get an internally regulated alternator.

We used the factory vacuum pump on the Cummins motor, and t'd it into the vent control lines and brake booster line. All accessories work fine.

Not sure how much of this helps you, but feel free to reply/contact me if you want any more info about Cummins swap stuff. Here's a pic of how it ended up...pretty clean IMO. Used the Dodge radiator and intercooler too.

I'd love to see someone on here put one in an MJ.

Click to expand...

Interesting... I don't suppose you can dig up some of your old notebooks on the project, could you? As detailed as that was, I'd like to see a lot more...

5-90

5-90 said:

Interesting... I don't suppose you can dig up some of your old notebooks on the project, could you? As detailed as that was, I'd like to see a lot more...

5-90

Click to expand...

Sure, what would you like to see? Although this probably isn't the most appropriate forum for it.

Although...I used an XJ coolant overflow bottle.







I've got documentation from the time we pulled the donor motor.

Actually, all of it. If there are a batch of pix, it may be easier to just Xerox the thing and send it to me - let me know how you'd like to work this.

This project is just different enough for me to really want to study...

5-90

5-90 said:

Actually, all of it. If there are a batch of pix, it may be easier to just Xerox the thing and send it to me - let me know how you'd like to work this.

This project is just different enough for me to really want to study...

5-90

Click to expand...

Well, probably the best resource is this:

http://www.fullsizebronco.com/forum/showthread.php?t=61534

where I posted the build thread (current up thru april, just updated it a little now because you reminded me of it).

I believe there's a mirrored thread of the build on Pirate but I can't search for it.

Again, if this needs to move to a different forum, my apologies.

Ok seems that we have the engine mechaincs figured out fule and wiring vacume ac that can all be taken off a dodge 5.9 na be made to fit. Now the Million dollar question will it physically fit in an xj??? Length wise according to cummins online specs it's about 30 in long I assume thats from very back of flywheel to the longest pulley so if so it's almost identical to a 4.0.

Next is width dosent looks too wide and since people but sbc in jeeps that seems like a non issue.
Height!!! damn this looks bad just from looking at pictures it looks really tall the mesurement that cummins gave me is 24 in tallMabey a hood scoop or cowl??? i dont know.

Weight it's damn heavy for a 4cly weights about 720 dry add all the accesories and your up to about 785 stock 4.0 weights in between 400 and 500 pounds..
So any weright you cut it it's about 300 pounds heavier. I dont see this as a very big problem after all peolpe add insane winch bumpers and all kinds of stuff on there jeeps.
I have a RE 5.5 lift with 4.5 coils and 2 in spacers worst case is I have to get 5.5 coils and 2 spacers of have a local spring shop bend me up some stiffer ones.

Heres the kicker I found 2 frito lay trucks next door to where I work in fact i can see tehrem while i type this there for sale at a lot right near me I did a little investivations One has a th400 with a 3.9 the other is a manual. There asking $1500 for the manual truck and $2000 for the auto both appear to be in decent shape but have about a million miles on them they both do run though.
Maye ill rebuild one kits go on ebay for abouth $500.

Time to bust out the torches!!!

we have 2 cummin's at school, 5.9's. its about 5" longer, 15" wider (including turbo), 6" taller, and its much more square than the 4.0 its well well WELL over 1000lbs, and would never fit

traitor5150 you should join the 4bt group on yahoo!groups. http://autos.groups.yahoo.com/group/cummins4BT/?yguid=122722016

the guys will post up links to the auction houses that sell allot of the bread vans, and you will get a heads up. They seem to go for around $1,500 for the vans with a good couple hundred being able to recyle the aluminum so say your out of pocket would be 1,100 for a runner and a day trip to go get it.

Not sure about putting one in an XJ. I DO WANT to put a tweaked out 4BT in a cj8 or if i can get a roll overTJ/LJ preferably an LJ.

Well, it's been a little while, but if you want to see the 6BT in action...

http://www.tcnj.edu/~macock2/stuff/broncocummins.wmv

and how it ended up:



Wouldn't have fit without a body lift in a Bronco, these things are really tall. Not sure about an XJ/MJ compartment. I think we're getting another 6BT shortly, and I may try in use it in my '79 full-size 2-door cherokee tow rig build up...

motorcityxj said:

traitor5150 you should join the 4bt group on yahoo!groups. http://autos.groups.yahoo.com/group/cummins4BT/?yguid=122722016

the guys will post up links to the auction houses that sell allot of the bread vans, and you will get a heads up. They seem to go for around $1,500 for the vans with a good couple hundred being able to recyle the aluminum so say your out of pocket would be 1,100 for a runner and a day trip to go get it.

Not sure about putting one in an XJ. I DO WANT to put a tweaked out 4BT in a cj8 or if i can get a roll overTJ/LJ preferably an LJ.

Click to expand...

I saw a just finished CJ-7 with a 4BT at the All-Breeds Jeep show in York last year. I didn't see it this year though. Very sweet set-up and I would definately loved one in an 8, the 7's are just too damn short.