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What About Converting from a Gas to Diesel Engine?


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Ok, this is more a hypothetical than anything else, but especially after some comments Moses made to me in another post, i just wanted to see how feasible it might be. What i am actually looking at is what all would be needed to convert two different dodge trucks to diesel.

 

One of the trucks would be my 1994 Dakota, which, as i have already posted about on here, some of you already know is a 4x4, with a 3.9l v-6. I also had a 1991 dakota that i toyed with the idea of converting to a diesel, mainly for longevity, and ease of maintenance, more than a desire to be able to tow heavier trailers, or anything like that, as i don't think it would be a good idea to go beyond Dodge's recommended trailer towing weights, even with a conversion like that.

 

What i am looking for, as i don't mess with diesels much, is besides the engine and corresponding wiring and electronics, what else would i need for a conversion like that? I know i would need the fuel tank, and associated plumbing as well as the engine and associated components, but, what im not sure of would be things like, does a diesel actually have an ECM? Can a diesel be connected to the existing drivetrain i have, which consists of an AX15 5spd manual, and transfer case, which i wish too keep the 4 wheel drive intact and functional, or would i be better off to upgrade at least the transmission to something heavier duty?

 

Which of the dodge diesels would be the best for a conversion like this, or, what about using a ford or chevy diesel? Are the diesel electronics, like their gas counterparts, separated by OBD1 and OBD2, and if so, what years did they start changing? I did read that the dodge diesel is an inline 6, whereas the ford and chevy diesels are v-8's. Would there be any advantage or disadvantage over an inline versus a v series engine? And lastly, at least for now, will a dodge inline 6 even fit in the dakota?

 

The other truck im thinking of a diesel conversion to is a 1993 extended cab ram 1500. It has a 5.2L in it now, but the engine is pretty much shot from the previous owner not doing any maintenance on it at all for several years, and it is just sitting around for now, while i decide what i really want to do with it. I know this truck originally came optioned with a diesel, so the engine fitting isn't a concern, but the same questions about the dakota, would also apply to this truck. The main difference driveline wise between this and the dakota is that the ram is still 4x4, but has an automatic, instead of manual transmission.

 

I was thinking of sourcing a complete wrecked Ram for the swap, so that i have all the necessary parts, such as exhaust, engine, wiring, ECM, and any other parts i might need.

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Can't leave this one alone, biggman100!  Quickly, some basics about why we want a diesel and the gains.  The main advantage of diesel power is much higher torque output, a quicker torque rise, and subsequently better fuel efficiency.  This higher torque has trickle down effects, including a much higher load on the geartrain and chassis.  Using your two examples of possible chassis choices for diesel swaps, let's look closer.

 

The Dakota has an AX15 that is considered by Chrysler the "lesser" transmission for a 3.9L V-6 versus the NV3500 for the V-8.  (This one's debatable, but we'll leave that alone for now.)  Diesel 2500 and 3500 trucks use NV4500 and NV5600 level torque ratings...The rear and front axles on your Dakota are lighter Dana units designed for the weight and load rating of your truck.  The frame is engineering to withstand the torque and loads of the V-6 or a smaller gas V-8.

 

A Ram 1500 has lighter axles than the diesel models, too.  While the engine bay will accommodate a V-10 or even the 5.9L inline Cummins diesel, this is not Chrysler's plan.  The only chassis intended for a 5.9L or 6.7L diesel is the 2500 HD or 3500.  Modular sections of the frame and torque/twist rating are much higher than the 1500, despite outward appearances that the bodies will interchange.  Axles for the earlier diesels are beam Dana 60 caliber, the later models like my 3500 use an AAM 9.25" front and an 11.5" AAM axle in the rear.  The rear springs stacks are enormous on the 3500 SWR, and the frame can handle both the spring rates and the axle sizing.  New 1500s are slated for a modern, higher speed diesel, and it will be interesting to see if the lighter duty IFS axle stays.  2500 HD and 3500 trucks still host a large beam front axle.

 

So, if I were considering a full-size Dodge 4x4 for diesel conversion, it would begin with the 2500 or preferably a 3500 chassis.  That said, there is also the chassis electronics as you hint, and yes, the diesels do use OBD functions.  (My truck is OBD-II, essentially, and the diesel engine does have a Cummins engine ECU.) 

 

If emission laws enter the picture, you must be in a state that allows diesel retrofit into a gasoline chassis for registration purposes.  If all of that is met by the state's standards (engine same year or newer than chassis, emissions in place, etc.), you would have the wiring to sort out, including any computer differences, and the engine's cooling system would need a dramatic upgrade to meet the diesel's thermal needs.  Transmission and driveline stamina would require diesel grade components. 

 

The Dakota might be a candidate for the rare and likely expensive recycled 3.0L V-6 diesel found in '05-up Grand Cherokees.  That would not be as much strain on the powertrain.  This engine might also be a candidate for the 1500; however, the truck's additional weight could prove self-defeating for this engine.  These engines were higher speed designs for Euro emission standards, and fuel efficiency, in my view, was not that impressive, especially for a Grand Cherokee.  Maintenance cost would be high, too. 

 

I can go further, that's the big stuff...The easier route is buying a used diesel model with the right history, and they're out there!

 

Moses

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Moses, once again, i am glad i asked you first. My plan doesn't seem like such a good idea, at least with the Dakota, from the way you explain it. As for the Ram i have, i don't see where it would be worth it, time and money wise, to swap everything over, because from the way you explain it, it looks like i would need to swap front and rear axles, and the entire drive train. What i think i will do instead is find a diesel Ram that the body is shot, which isn't hard in my neck of the woods, and just swap the body i have on my Ram, over to the diesel.

 

The Ram i have, the body is in excellent shape, because it came from southern PA, where they don't use salt on the roads, and i got it dirt cheap, because the engine is pretty much shot, and there is supposed to also be issues with the transmission as well. I figure i can get an older diesel ram, mainly pre-1995, do the body swap, and then later, when finances are better, have a better candidate for a trade or to sell outright, to offset the cost of the newer truck.

 

As for emission laws in NY, as long as the vehicle is made before January of 1996, there really isn't any defined laws about swapping things such as engines and transmissions from older years, at least not yet, which is why my trucks are usually 1995 or older. The laws aren't really as strict on swapping say a 1996 engine into say a 2000 vehicle, but the MIL has to be off, and have been off at least for the last 3 key cycles, or 65 miles of driving, whichever comes later, and up until 2000 can only have 3 monitors incomplete, and up until 2003, can only have 2 monitors incomplete, and up until 2006 can have 1 monitor incomplete, and after 2006, can have no monitors incomplete, and no pending or showing codes are allowed for any vehicle made after January 1996. NY doesn't do the California style emission and smog test either, at least not yet, give it time.

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Very interesting about New York emissions law.  California, essentially, is that the engine must be the same year or newer, the emission controls must all be in place, and the vehicle must pass emissions equal to or lower than the OEM engine in good operating condition. The engine must also be from the same emissions "class" of vehicle. 

 

From a diesel standpoint, if I wanted to install an Isuzu 3.9L diesel into my Cherokee, which I actually wanted to do, that would not be acceptable in California—regardless of the tailpipe readings.  The Isuzu four-cylinder diesel is only available in medium-duty trucks, and the Cherokee is in the passenger car/light duty truck emissions category. 

 

Catch-22:  For many years now, the Jeep Grand Cherokee, Liberty and BMW's SUV have been the only U.S. market, light duty emissions SUV or truck models (1/2 ton capacity to 6000# GVWR) built with a diesel engine.  Prior to these recent developments, the only diesel engines offered in light-duty emissions, full-size trucks and SUVs were the ill-fated GM 350 and the improved GM 6.2L V-8 models of years ago—and for swap material, both of those GM engines would fail the "same-year or newer" California guideline for a swap into a '99 XJ Cherokee.  The 6.5L GM V-8 does not qualify, nor would a Duramax, as they were only installed in medium-duty emissions class vehicles (2500-series and higher GVWR). 

 

It's not coincidence that diesels in recent times, like the 6.5L GM, the Duramax, the Ford Navistar V-8s, and Cummins' ISB engines are only found in 3/4-ton and bigger trucks.  This is in part due to the chassis, geartrain and axle differences I've shared: Also important, these engines were not able to meet light duty passenger car/truck to 6000# GVWR emissions.  If new Ram 1500 trucks come out with a light duty emissions legal diesel engine option (more than rumor), that could be a future "donor engine" for a vehicle like our 1999 4WD XJ Cherokee, albeit very expensive, or for a swap like a Jeep Wrangler. 

 

The fact that the Isuzu 3.9L in current form has a very good emissions record means nothing, the California regulation is arbitrary and very likely a precedent for any EPA or multi-state standard as well.  Given this situation, the current diesel swap engine for California-legal emissions is something like a VW TDI (passenger/truck light duty class emissions), a Volvo diesel or a Mercedes diesel car engine, each very expensive, with questionable performance in a 3800#-plus curb weight trail/street Jeep. 

 

This conundrum has been the basis for endless consumer requests, in particular the J-8 Egyptian military 2.8L four-cylinder diesel in the JK Wrangler.  Consumers have wanted that engine in the TJ and JK since the Liberty CRD came to 49-State market.  This 2.8L engine could solve a lot of issues, it's essentially the Liberty CRD diesel, made in Italy, very reliable, though small in displacement.

 

To be continued, I'm sure...

 

Moses

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Here's a link to the future!...Now at Mazda, apparently, a lower compression diesel with high tech injection and variable valve lift and timing means lower emissions, plenty of power, great fuel efficiency, and that our "diesel now" request for light duty emissions cars, SUVs and trucks has an answer:  http://www.economist.com/blogs/babbage/2013/07/diesels.

 

The diesel may well keep the internal combustion engine alive for the foreseeable future...These lower-compression diesels need to be the backup in hybrids like the Prius...Advancing emissions technology must eliminate the need for exhaust urea and expensive soot removal devices....

 

Moses

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Mazda is on the right track, as long as they actually produce it for the U.S. market. I have heard quite a bit about how in Europe diesels are a lot more prevalent, and gas engines aren't as big over there, but in this country it is the opposite. I'm not sure why that is, but i have some thoughts on it, that usually when i bring them up, i get odd looks from people.

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Well, for just a hint, Europeans are very conscious of reducing their transportation costs, and fuel sells for upward of $7 U.S. per gallon equivalent in many places.  As a footnote, there is so much diesel market in Europe that U.S. oil producers find it lucrative to sell diesel fuel there.  This is one reason why we pay an inflated price in the U.S. for a less expensive to produce fuel. 

 

Diesel fuel, involving less production cost as a whole, is now $0.50 per gallon higher than unleaded regular at our area.  At one time, it was assumed that diesel fuel would always sell for less than regular gasoline.  (That's another reason many of us wanted to own diesel vehicles!)  And Low Sulfur Diesel fuel is not the reason for the high price, it's just the excuse...

 

One practical solution is biodiesel.  This fuel, however, needs to be more efficient and yield a cleaner crankcase.  The GDiesel process on biodiesel stock would be a sensible, long-term solution for diesel engine fuel. 

 

Moses

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Diesel prices here are about in line with the difference you show in Nevada, they range between $0.40 and $0.60 higher than unleaded around here. Thank you for the link to the GDiesel article and video. A couple of the farmers around here operate large farms, and even though they aren't using it so much for on road vehicles, they are always looking for ways to cut fuel costs for equipment. We have been discussing biodiesel for awhile now, but with the chemicals involved to produce it, they aren't exactly keen on the idea, so any idea that not only will allow their equipment to be run cheaper, as well as possibly be better for the equipment overall, would be of huge benefit to them.

 

One of my theories on why diesel, and even regular gas is so high, is simply because with so many people on the roads driving, they know that it will always be money in the bank. I know they have production costs, employee costs, delivery costs, but, when the companies post quarterly earnings in the billions, every quarter, they can afford to drop the price some. As for why regular gas is so much more prevalent in this country, the companies have found out many ways to make money from it, and not just the fuel companies either, but the auto manufacturers, and even the government, make big dollars from regular gas in this country.

 

Now, before you say im crazy, ask yourself this one simple question:  "Why is it that diesel engines will go many miles before even minor work, other than routine maintenance, is needed, and some newer gas engines wont last 100000 miles?"  Look in the owners manual of any domestic car, and even most gasoline powered trucks, and you will see a life limit, usually 100000 miles, before vehicle replacement is recommended, but i have never seen that info in a diesel owners manual.

 

My theory on why diesel has risen so much the last few years is simply because more people are buying it in this country. Before, it was only heavy equipment, tractor trailers, and farm equipment that used diesel, but now more and more people are buying trucks with diesel engines, from the guy who tows heavy trailers, to the soccer mom who wants better fuel economy and longevity in a vehicle. Its all about supply and demand. You demand it, so they supply it at their price.

 

Here is a link i found from Exxon Mobil, about where gas dollars actually go to. It is a short article, but makes interesting reading. The link is http://www.exxonmobilperspectives.com/2011/04/30/where-do-your-gasoline-dollars-go-2/.  They say more of your gas dollars go to taxes, than actually go back to the oil companies, which means if the oil companies post returns in the hundreds of billions every quarter, how much is the government taking in, and, if so many tax dollars go to the government, why is the national debt still so high? Not trying to start a political debate here, i just thought the link was somewhat relevant to our discussion.

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Good points...As for volume demand, that's true of all motor fuels, and it's also interesting to note the comment from the Chevron CEO when asked at a hearing why pricing is so high in a supposed "supply and demand", free-market economy.  His response, in essence, was that there is a demand, and the oil companies charge what they can get, not based upon supply.  This is unique to a free enterprise marketing model, and it fits your comment about there being a demand for a commodity which we depend upon.  There is no alternative to fossil fuel at the present, and the entire country is dependent upon an infrastructure that demands vehicle ownership, truck transportation and driving on public roads.  This is total dependency, not demand. 

 

Mass transit is looked at with derision in many circles, like we're somehow giving up a basic American right.  Alternative fuels have really had no push, prospects like algae fuel might actually break "foreign energy dependence" once and for all.  We go on with this thing culturally, because we as a society have subscribed to a belief system around the "freedom" of using automobiles, trucks and other motor vehicles to meet our transportation needs.  In the process, we have collectively created a green light for oil companies to set any price they want.  There is no freedom of choice, fossil fuel at the pump from Exxon-Mobil and Chevron is a necessity...And as prices continually bump upward, we haven't seen a significant public reaction yet.

 

Your point about taxes and government are well taken, too.  Sounds like governments, both state and federal, have something to gain from motor use fuel taxes.  At the very least, these taxes pay for our transportation infrastructure improvements and road maintenance, plus they fund lifetime state and federal agency workers who are taxpayers, plus they create many private sector jobs at road construction and maintenance.  Yes, it's the transportation "system".

 

Despite the cost of fuel and the taxes, we continue to drive as usual...This week is Hot August Nights at Reno, an all out celebration of the automobile culture and the "good old days"—the contemporary subtext to this is our dependency on oil companies...The time honored caveat:  "Be careful what you ask for..."

 

A home-based biodiesel station sounds more appealing all the time...As fuel pricing continues to rise and profits at Exxon-Mobil and Chevron reach new heights, at some point it could become cost effective to cook up our own fuel for the Dodge Ram 3500 4x4...By that time, however, the state and federal governments will likely devise a way to collect motor use tax on homespun fuel, so we'll have to factor that expense into the equation when considering "cost-effectiveness". 

 

Moses   

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About biodiesel, i have heard different initiatives in the works so the government doesn't lose the taxes from it. Everything from road use tax increases for diesel trucks, to increased taxes on the base chemicals used to produce biodiesel, to even higher registration for diesel trucks, regardless of weight class.

 

About the mass transit debate, if you will, that seems to depend on where you live. In New York City, for example, most people have no problem with mass transit, same with places like Rochester and Syracuse, NY, but then you go to smaller cities, such as Elmira, Corning, Central Square, for example, and mention mass transit, and i have actually seen people cringe at the thought, but at the same time, they are the ones always complaining that they spend too much to drive their vehicles.

 

Certain places, like the small towns around where i live, have actually gotten rid of mass transit, due to no return on the money they spend to keep it operating, because everyone around here thinks they cant get anywhere without their own vehicle. I myself don't see an issue with mass transit, and i have seen where it can be a major money saver, but at the same time, can be inconvenient, in that if you have to be at work, or an appointment at a certain time, and say you take a public bus, and get there 55 minutes early, then what do you do? The question i hear quite a bit, "Is the inconvenience worth the money saved?"

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We live at the Far West in a semi-rural area.  Mass transit typically does not serve outlying communities, and we're typical for most non-urban areas.  The infrastructure, especially the interstate highway system, sealed the fate of outlying communities, on the one hand connecting key cities and regions, on the other hand avoiding mass transit.  Ironically, all of the smaller, rural communities where we have lived once had passenger rail service.  Those rail services disappeared with the emergence of affordable motor vehicles and cheap motor fuel. 

 

Pros and cons of mass transit will likely be debated for a very long time.  The one thing that is certain is the incredible increase in fuel costs.  As a teenager, I pumped Hancock and Chevron regular leaded fuel (94 octane!) for as low as $0.219 per gallon in a 1963 gas war to $0.349 when I graduated high school in 1967.  Consider the percentage of the average American's income that now goes to annual vehicle fuel expenses and the overall cost of vehicle ownership.  I'm not referring to adjustments in wages or anything like that, simply, what percentage of your income now supports your vehicle(s) and fuel needs?

 

I'm going to bow out here, as this discussion has strayed from four-wheel drive light truck, Jeep and SUV mechanics, dirt motorcycles, ATVs, trailers, destination travel and other forum categories.  We'll discuss something more uplifting than the cost of motor vehicle fuel...

 

Moses

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True, biggman100...It's enough to cover 4WD truck, Jeep, SUV and other off-road technology, to help folks keep a 4x4 running safely and reliably, and to enjoy our backcountry travel...Though we do like constructive, even spirited debate, we'll stay on topic.

 

Moses

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  • 1 year later...

Moses, i was getting gas today, and saw a 1998 Dakota that someone had done a diesel conversion on in Pennsylvania. He used a Yanmar sourced, Cummins turbo diesel. He let me look it over, as well as showed me some of the downsides to the conversion, the biggest being getting the engine fitted properly, the fuel tank mounting, and wiring and electronics. He said this is the second one he has done, and didnt have structural issues, such as the frame being too weak, but did have issues with the engine he used being too underpowered for the swap, which gets me to wondering, if he used a 6 instead of a 4 cylinder turbo diesel, would that end up being too much torque for the chassis, or would it actually work. after seeing his truck, im curious about it, but, with the cost involved, im not sure if i would want to build one or not.

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Aside from emission legality and getting a vehicle smog legal at California, New York and many other states now, the four-cylinder engines seem the limit for a lighter 4x4 truck.  Fit-up for the 5.9L Cummins (ISB or "In-Line-Six") engine would be troublesome, and the Cummins ISB engine is not even a candidate for Ram 1500 model frames or geartrains. 

 

From what I've seen, the successful swaps are the 3.9L "bread truck" engines or Cummins 4BT.  Here is a listing from an aftermarket rebuilder that includes both "off-highway" (construction) and automotive/truck applications:  http://www.pilotengines.com/servlet/Categories?keyword=Delivery-Cummins-3.9L-B-Series.  This is not the cleanest burning engine but very reliable. 

 

The engine that I had targeted for the magazine's very own XJ Cherokee was the 3.9L Isuzu diesel four.  Later, larger versions of this engine have very clean tailpipe readings and can put out considerable power.  In my research for 50-State legal possibilities, California had closed the window on this kind of swap in 2009, as the Isuzu applications are medium duty truck chassis, and the XJ Cherokee is "passenger car/light truck" category for emissions.  That left me with the Euro turbo-diesel passenger car engines like the Volkswagen TDI, and I lost interest.

 

Here's the Isuzu 3.9L in its many forms:  http://www.busbeetruckparts.com/isuzu-engines?gclid=CjwKEAiA7ZajBRCpur2xi47n1zkSJADqV2WlR3X_K333j_iVS2-PDri4Mp76xe6Y8Uz4nlxdfYoIFhoCsVTw_wcB.  Or try this complete run-down for Isuzu engines and applications:  http://en.wikipedia.org/wiki/List_of_Isuzu_engines.

 

There is a firm that makes an adapter for the 3.9L Isuzu to a 700R4 GM transmission, and my guess is that they enjoy a reasonable market for those who don't face smog obstacles.  We should be able to do this swap legally as before 2009 in California—only required a change in fuel type on the registration!  Better tailpipe emissions are clear, which is supposedly what smog agencies care about.  Either the Cummins 4BT or an Isuzu 3.9L or bigger inline four sound appealing!  For weight savings, the Isuzu inline four diesels have the advantage.  In either case, the flywheel is massive and heavy.

 

Moses

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In new york, anything pre-1996 is exempt from emissions, so pretty much anything goes here, as far as engine swaps. I have a friend with a 1992 Chevy 4x4 with a 1970 Cadillac 500 in it. Why, im still not sure, but it goes to show, just about anything can be done with the right amount of work and time.

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I have seen a couple Ford Rangers with the 3.9L Isuzu engine in them around here. Those engines are actually plentiful at a couple wrecking yards locally, due to having several companies that use them in large amounts. The biggest issue i see around here though, is that people usually put big, dual exhaust pipes through the bed, and they just pour black smoke, usually due to them not being properly maintained, but, as N.Y. doesn't seem to care what the vehicle has in it pre-1996, they can get away with it. I have also seen a couple newer diesel Dodge Rams with massive, 7" or larger stacks, that not only blow a ton of black smoke, but, are annoyingly loud.

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