Today, we take diesel trucks for granted. They provide huge torque, good fuel economy, and are the solution if towing is your game. But it wasn’t always like this. Go back in time to the late 1970s, and diesel pickups were only just hitting the market. Chevy was the first major American automaker to take a proper swing at a diesel truck, but the result was an engineering disaster that stuck around for just four short years.
If you’re a diehard car enthusiast, you likely already know about this engine, but I just want to write about it today. GM’s first experiment with diesel powered trucks was with an engine that would go down in infamy. Modern Chevy trucks are well known for packing Duramax diesel engines, and prior to that, the company’s pickups relied on trusty Detroit Diesel powerplants, all the way back to 1982. But before that, GM’s efforts hinged on a cursed powerplant known as the Oldsmobile diesel, engine code LF9.
Like I said, you’ve probably heard of this engine before; it starred in the Oldsmobile Delta 88, and stuck around there for a full seven years. It also showed up in a bunch of Buick, Chevy, Cadillac, and Pontiac cars. Few remember it fondly, and even fewer remember that it was actually available in Chevy’s half-ton C-Series pickups from 1978 to 1981. It would prove unreliable, unpopular, and ultimately, forgettable. But why was it so bad?
Slap It Together
To understand the folly of the Oldsmobile V8, and the trucks and cars that featured it, we need to look at its development. In the 1970s, GM was rushing to find a solution for the stringent fuel economy and emissions standards that were hitting automakers hard in the midst of the gas crisis. Diesels looked to offer potentially better fuel economy than big V8 gas engines at the time, and there were different emissions standards for diesels, too. The project got dumped on Oldsmobile’s desk, with the automaker charged with developing a diesel V8 that could power cars and trucks across GM’s range into the next decade.
Oldsmobile engineers decided to start with what they knew, and based their work on the existing Oldsmobile 350 cubic-inch V8. It was this decision that played a role in the failures to come. That’s because a diesel engine typically runs at a far higher compression ratio than a typical gasoline engine. A gas engine might run at somewhere between 8:1 and 12:1, while diesels typically run from 14:1 to 22:1. This is mostly because gas engines are desperately trying to avoid compression ignition of the fuel, while diesel engines rely on that same effect.
The engine’s designers took this into account to some degree, designing a reinforced block for the diesel application. Other changes included hardened camshafts, larger main bearings, and tougher, thicker connecting rods and piston pins.
For all that the engineers did, they didn’t go far enough. The diesel engine’s heads used the same head bolts and 10-bolt pattern as the gas engine. This decision was made to allow the diesel engine and gasoline engine to share some of the same tooling. However, it meant that the head bolts were extremely overstressed in the diesel application. They were more than capable of handling the cylinder pressures of a gasoline engine, but they couldn’t take the additional strain of the high-compression Oldsmobile diesel design, which ran at a lofty 22.5:1. The design really needed more head bolts, and likely stronger ones too, but budget concerns won the day.
As covered by Popular Mechanics, the result was that the engines readily popped head gaskets when the bolts stretched or snapped in the field. This would typically be followed by coolant entering the cylinders, with the additional threat of hydrolocking causing major damage to the engine’s rotating assembly.
An actual running example of an Oldsmobile diesel V8. This is marked as a DX block, suggesting it’s from 1981 or later, though the video states it’s installed in a 1978 model C10. Few of the original engines from 1978-1980 survive as runners as they were just that catastrophically bad.
Another short-sighted move was that the engine was designed without a water separator in the fuel system. It’s sadly not uncommon for diesel fuel to be contaminated with water to some degree, and this was especially the case in the late 1970s. A lot of diesel engines include a system to separate water from the fuel before it reaches components like the injection pump or the engine itself, to avoid corrosion in delicate mechanical parts with tight tolerances. GM’s engineers simply thought this wasn’t important and left it out, which meant corrosion often ended up fouling injection pumps, injectors, and fuel lines in the Oldsmobile engines. Some owners would try and use a product called “dry gas” to try and deal with the water content; often this was a preparation of methanol or isopropyl alcohol that would allow the water to more easily mix with the fuel and burn off. However, in the diesel Olds, this product tended to ruin seals in the pump and cause further problems.
A further issue was that the timing chain responsible for running the injection pump often stretched to the point of failure, too. In any other car, that would be a major headline failure, but it was pretty minor in comparison to the Oldsmobile diesel’s other foibles. Camshafts also tended to wear flat, in part due to a customer base not familiar with diesel-specific oils and the more frequent oil changes needed to deal with soot and contamination.
Hilariously, the problems with the Oldsmobile V8 were so bad that GM couldn’t even sell them in California in 1979 and early 1980. Why? Because the test cars suffered repeated failures and couldn’t complete the state’s emissions tests.
But surely the Oldsmobile V8 offered good performance when it was running, right? Well… not really. The engine was designed more for efficiency than performance. It had neither the most power nor the most torque of all the engines GM offered on the C-series pickup at the time. From its 5.7-liter displacement, the naturally-aspired engine offered 120 horsepower and 220 lb-ft of torque, using indirect injection as was the style at the time.
At best, the Oldsmobile motor would offer slightly better power than the base 4.1-liter inline-six, which only had 105 horsepower and 185 pound-feet of torque in 1978. It was about equal on power with the 4.8-liter inline six, and couldn’t hope to keep up with the gas V8s from the rest of the Chevy range, which topped out with the 7.4-liter big block good for 240 hp and 370 pound-feet in its most powerful configuration.
Where it really shined, though, was in fuel economy. The diesel C10 could get 20 mpg in the city and 28 mpg on the highway—pretty stellar figures for the time. In comparison, the base inline-six would get 16 mpg and 22mpg respectively. You’d get more power out of the big-block V8, but you’d suffer when it came to the bowser. It posted just 12 mpg and 16 mpg respectively.
The diesel was only available on two-wheel-drive models, so it was limited in its appeal. But if you wanted a cheap truck to get around while (comparatively) sipping fuel, it offered a compelling solution. Unfortunately, the reliability wasn’t there to justify the hassle.
Fallout
The obvious result of all these problems was that this demon donk actually spawned multiple lawsuits. One well-known class action was started by Peter and Diane Halferty, customers who had grown increasingly frustrated after two engine replacements and a transmission swap under warranty still netted them a dead car. Ultimately, the FTC got involved, and a major class action ended in GM having to pay up to 80% towards engine replacements for affected customers.
Contemporary coverage by the New York Times in 1983 included quotes from ex-G.M. engineer Darrel R. Sand, who had helped develop the Oldsmobile diesel V8:
In test after test, we had broken crankshafts, broken blocks, leaking head gaskets and fuel pump problems. The diesel couldn’t hold up, it was a hastily converted gasoline engine with a fuel pump designed for heavy trucks.
In the article, Sand claimed that he had told his superiors at GM that the engine should not be put into production in 1977 and 1978. According to the engineer, his warnings fell on deaf ears, as GM badly needed the diesel V8 to help meet increasingly stringent fuel economy standards. Ultimately, Sand would retire from GM in 1980; he alleged that GM had forced him into it as a result of his protestations about the V8.
The Oldsmobile V8 was eventually replaced in the C10, with the 6.2-liter Detroit Diesel V8 taking over for the 1982 model year. It was available on half-ton, 3/4-ton, and 1-ton pickups, unlike the Olds unit. It had a touch more power and torque, starting at 135 hp and 240 lb-ft, and the naturally aspirated engine still relied on indirect injection.
The Detroit Diesel engine had important equipment that the Oldsmobile lacked, like a water separator and a block and fuel line heater to aid starting. The main thing, though, was reliability. Where the Oldsmobile unit couldn’t always be trusted to get you to from Tampa to Atlanta, the Detroit Diesel could take you to Baghdad and back if you were so inclined. That’s because from 1982 to 1993, the same engine played a starring role in the AM General HMMWV, better known as the Humvee.
Despite its reputation, the cursed Oldsmobile diesel nonetheless stuck around until 1985 in some Buick, Cadillac, Chevy, and Pontiac applications. That’s because GM got the design to work after the first few awful years by redesigning the heads and bolts and various other modifications. By 1981, the “DX” version of the Oldsmobile diesel V8 was much improved, and a 4.3-liter diesel V6 was also offered from 1982. And yet, as far as consumers were concerned, the damage had already been done. Having been eliminated from the C10 in 1982, Oldsmobile diesels of both types would cease production entirely after the 1985 model year.
It was an inauspicious start for diesel pickups in the US. Dodge had a false start, too, which is a story for another time. Meanwhile, Ford avoided much of the embarrassment as it held off on launching a diesel pickup of its own until 1983. These days, diesel trucks are stout and capable workhorses of great capability, but on their entry into the US market, they were anything but that.
Image credits: Chevy, GM, Oldsmobile, Always Another Project via Youtube Screenshot
“According to the engineer, his warnings fell on deaf ears, as GM badly needed the diesel V8 to help meet increasingly stringent fuel economy standards.”
Man what a typically GM move, advertising truly does wonders to keep people buying stuff.
Didn’t get to experience this in a truck. Did have an 83 GMC with the “good” diesel. Was actually my wife’s vehicle when we got married (I picked a winner!). Tan and white 2-tone. GM certainly did make an improvement there. Wasn’t real fast or powerful, but ran forever and got 30+ highway. Amazing for a 1/2 ton truck.
Did experience the Olds diesel in a rather unique form, though. In high school (late 80’s) a buddy was showing off his new ride. A beautiful T-top Monte Carlo. Only 4-5 years old at the time. That was a big deal! (I was driving a ’78 Fairmont) Then he fired it up, and it sounded like the trucks and tractors we farm boys were all used to! Why would anyone check the boxes to build a Diesel Monte Carlo?
he alleged that GM had forced him into it as a result of his protestations about the V8.
And that is the kind of crap that makes a STEM labor shortage.
Honestly. I got a mining degree and was working for a quarry and the way they treated basically everyone at the site made me leave the position two months in and go work a labor job for 4 months. I’d love to work in mining, but of the 12 or so sites I’ve worked at, exactly one of them wasn’t run by a complete moron. The same company I was at was also constantly posting on linkedin about the engineering talent shortage and that sort of stuff, and it’s really no wonder they can’t keep anyone long term. They basically have to trap you there.
The myth of the shortage baffles me. In my entire career in STEM I’ve seen absolutely no evidence of a shortage but plenty of evidence of a surplus.
Mining does have a shortage on account of nobody going into it, but to be honest it doesn’t need to be its own degree. Any civil or mechanical engineer that spends a summer at a mine could do the same work a mining engineer does. The companies brought it upon themselves, they did no outreach or community involvement for decades, and have done little to improve their image as an undesirable degree. Heck, most people I knew in school didn’t know mining existed as a degree until after they met me or one of my classmates, most of whom transferred from other degrees for one reason or another. And the number of times I was asked “mining? Like with pickaxes?” was comical.
Any shortage of engineering talent at mines is completely their own fault, whether it’s because their site isn’t a good place to work or because mining companies are too picky. Either way it’s entertaining to spectate, if a bit unfortunate for the future of the industry in the US.
Any shortage of engineering talent at mines is completely their own fault, whether it’s because their site isn’t a good place to work or because mining companies are too picky.
And that by definition does not constitute a shortage.
A shortage is when you have absolutely nobody qualified to recruit even with an offer of a generous compensation surcharge and good working (like not life threatening) conditions . When companies start paying good money and working to keep anything that can fog a mirror, THEN they can complain of a shortage.
Yeah it doesn’t seem like they’re willing to do that yet, they’re going to complain about it regardless though.
And why not? Its not like it costs anything and it’s not like anyone is fact checking.
Here’s one for the gearheads in the audience.
Has anyone ever heard of an engine that was essentially an “inline flat” 6-cylinder? i.e., a single row of six HORIZONTAL cylinders, not vertical ones? I’m kind of playing with the idea of such an engine, modified from an existing, very conventional water-cooled inline-six into something air-cooled.
The idea is that making the engine flat and wide, but air-cooled, increases reliability by removing potential points of failure, and orienting the cylinders in a single flat row makes the engine take up less vertical space, which is important in this case. The engine I’m starting with is already known for being reliable/etc, but I want to really pump that up to 11 in as many ways as possible. (It would also have a lower compression than the original water-cooled design, for instance.)
I don’t want to say too much about which engine and why, because this is something I might actually send in, if I can get my thoughts down on paper in both word and art, but I will say that it’s based on a previous Autopian article.
Slant I6 yes, horizontal I6 no. That kind of engine would have a way off center drive line if its centered in the engine bay unless you centered it with a chain or gears. That’s going to add weight and complexity.
I guess I’ll have to provide one more detail for context. This is for a hypothetical rear-engine, rear-wheel-drive vehicle. The way I picture it, the block is in the center, transverse, with the cylinders all pointed forward. The alternator, HVAC compressor, battery, etc are all at the rear of the engine, easily accessed by a mechanic. Air is brought in from the sides and cools the cylinders via fan before reaching the engine intake filter.
But I’m just one idiot with a bunch of dumb ideas.
So for a R/R setup like that right off the bat I’d reverse the engine so the crankshaft was on the inside and the cylinders pointed to the rear. That would make valve work easier. I’d also have the engine driving the transmission in a center T drive like Ford did in a prototype series on inline engines in the 1990s.
I’d then run the heat pump and power steering electrically. That would allow them to be placed anywhere. Only the alternator and oil pump would be driven by the engine. Packaging those might be a challenge though while keeping a reasonably flat deck.
Still I think water cooling would be a better for such a setup. Even Porsche gave up on air cooling. An electric water pump could be placed at the low point of the system, maybe integrated into the radiator and spun just fast enough to meet cooling needs thus eliminating the thermostat.
Older tech. Sorry.
??
No heat pump — HVAC air conditioning and an engine-coolant heater. No power anything.
Air conditioning is a one way heat pump. The kind I’m talking about runs backwards as well which would provide heat for your coolant free air cooled vehicle.
If however you are making it liquid cooled after all a standard heater is better.
Deutz currently makes inline-6 air cooled diesel engines, and has for a long time. They are upright, but I guess you could make some design adjustments to make it a flat inline 6.
Well crap, now you’ve sent me down a Deutz air-cooled diesel rabbit hole which leads to such fascinating builds as a diesel 3-cylinder Ford Ranger build with 52 hp that gets 40 mpg on waste oil. I irrationally want one so bad now.
You may be delighted to know that Cummins almost got third place in the Indy 500 with such a design. They wanted to prove the versatility and power of their diesel inline sixes in a unique way, so they built a unique Indy car with one of their regular diesel straight sixes leaned almost exactly flat, adding a turbocharger, and converted to a dry-sump oiling system. At the time, the rules for the Indy 500 allowed for more powerful diesel engines than gasoline ones due to the increased weight of diesel drivetrains. Cummins proved the power advantage could overcome the weight disadvantage, and the engine laid on its side gave the car a low center of gravity with fantastic handling. Unfortunately, in its debut race, the turbocharger sucked up track debris, causing damage to the car too late in the race to be repaired, but the car had held third place for enough laps by then that it was a massive PR success and gained Cummins a significant number of new customers. The next season the loophole in the rules was closed, making diesel engines no longer competitive and ending Cummins’ chances to win future races, but by then they’d gotten their publicity and didn’t care. Many decades later however, they decided to restore the car to show off at various events, and while rebuilding the engine they discovered cracks forming in the crankshaft… so it turns out that the turbocharger ending the race prematurely for them may have been a blessing in disguise. Still a very interesting and impressive car.
Oh wow, thanks! That’s quite a tale…
I am dying laughing at the idea that you could get 12/16 mpg out of a big block. Our family towed with a 78 GMC with the 454. Great tow vehicle, but terrible daily. Got more like 5/8 mpg without the trailer and a little less with it.
I know this is nitpicking, but this was America in the ’70s.
You wrote: “At best, the Oldsmobile motor would offer slightly better power than the base 4.1-liter inline-six, which only had 105 horsepower and 185 pound-feet of torque in 1978. It was about equal on power with the 4.8-liter inline six, and couldn’t hope to keep up with the gas V8s from the rest of the Chevy range, which topped out with the 7.4-liter big block good for 240 hp and 370 pound-feet in its most powerful configuration.”
In 1978, if you wanted a gas engine, you could get the C10 with a base 250 cu. in. inline-six, an optional 292 cu. in. inline-six, 305 cu. in. V8, 350 cu. in. V8 or a 454 cu. in. V8.
Nowhere in the 1978 sales brochure does it say anything about liters when it comes to gasoline powered engines. It does call the diesel as a 5.7 litre (350 CID)
You can read the entire brochure here:
https://www.xr793.com/wp-content/uploads/2017/07/1978-Chevrolet-Pickups.pdf
Is it wrong that I want one of these now?
Same. I kind of want to build a turbo DX motor and see if it could come good
If memory serves, these are actually pretty popular in niche racing communities, albeit converted back to running on gasoline
The DX blocks are monstrously strong. Joe Mondello pioneered the diesel-to-gas conversion of them, ending up with a 440-inch smallblock making over 450 horsepower on pump gas.
Can confirm on the head bolts. I ripped a reman DX-block engine out of a car and one of the head bolts was missing the head.
Curiously I have two of them now, both waiting for a Lemons car that has never come about.
Growing up a guy on our street had an excavating company that he advertised on all his vehicles, that were all parked on our street. He bought two of these when they came out and lasted about six months before he gave up on them. He really wanted the cheap offroad diesel that he used to power everything.
Do you have a primary reference on this? In my experience most decisions like this come from accounting, not engineering. Things like removing the front sway bar on the Corvair to save $10 per car.
Exactly, this should read “GM’s engineers’ managers thought this wasn’t important.”
I remember reading this was a cost-based decision, as were a lot of the decisions that killed this engine.
There is NO WAY the engineers involved thought the head bolt count and pattern on that engine were suitable for the static compression ratio planned; that choice was made not by engineers but by accountants to keep the cost down by not requiring new machine tooling.
I know the cost of the diesel option was a big worry so I think they were punching every penny.
I think they were punching every penny.
Those pennies had it coming!
“The diesel was only available on two-wheel-drive models, so it was limited in its appeal.”
In the 1970’s the majority of trucks on the road were 2-wheel drive. It wasn’t until the Dubya years that it became unmanly to drive anything except a full-sized, American, V-8 powered four-wheel-drive pickup truck.
I have worked in engineering, product design, and management. I have seen many decisions made that everyone in the room knew was wrong. This includes products with inadequate hardware (like weak head bolts), unfinished software (ship it, we’ll issue an update) or flying in the face of human nature (just tell the user not to do that). It always always always ends badly.
PowerShift another great example
My introduction to this engine was a Blazer my dad bought from a neighbor that was running the diesel. That was a highly unreliable POS. I’m fairly sure that within a year my dad had the engine swapped out for a gas 350. Used and tired, but it was still way better.
My first car was a 1980 Olds diesel Custom Cruiser with the fake wood trim. It was a fantastic car in every respect. Except the engine.
True fact: We got 30 MPG on the freeway.
Also True Fact: It was dangerously slow. It was dangerous to merge on the freeway.
The car finally met its demise when I was 17. I was driving with a buddy back from his parent’s cottage, and heard a huge “Ting!!!”, and I lost all power. Could barely make 45 mph. These girls drove up next to us, and we thought we were going to be all cool. Then one of the girls holds her nose, and points to the rear of the car. Billowing smoke.
I ended up racing my car against another friend; me in the Olds, him on foot. He beat me for two blocks, until I got a head of steam going.
Again, the rest of the car was really good. A quality, comfortable, well built and handsome car. But that engine….
These girls drove up next to us, and we thought we were going to be all cool.
Really? In an Oldsmobile diesel?
These created a mini industry doing diesel to gas engine swaps. I remember the adverts in the classified section of the “newspaper” back in the 80s.
My understanding is that the reinforcements for turning it into a diesel were actually prized by hot rod builders converting them back gas.
I was coming here to say the same. Beefy enough to hold significant boost on gas if you swap out the heads for gasser heads, which given the identical bolt pattern, is a piece of cake.
I believe you also have to replace the crank to get the compression ratio back down below 12:1, but yeah, that is the gist of it.
The crank does not determine the static compression ratio.
It uses the same stroke and bore as the gas engine so the same throw on the crank. I *think* it uses a shorter rod and tell piston but I am not sure on that.
It also has a larger main bore so you can’t just throw a gas crank in it without bearing spacers.
The crank *alone* doesn’t, but the stroke of the crank is the single largest factor.
Right, but the diesel and gas engine share the same stroke so that’s not changing anything.
And it’s not if anyone is changing crank throw and using the same piston unless you want like 4:1 compression or a piston hitting the head…
Yeah, you are right that stroke isn’t the only factor. I recall reading about a conversion kit and knew it was more than just new heads. Crank made the most sense to me but I seem to recall being surprised that it included pistons and rods.
The diesels used a tall piston and shorter rod.
They could also be bored 0.100″ over with little concern.
I think the biggest upside was cars originally equipped with the diesel engine, as indicated by the VIN, were exempt from emissions inspections in Virginia regardless of what engine had later been swapped in.
The saddest part about the Olds Diesel debacle is, you guessed it, it’s yet another example of GM getting it right after it’s too late. The biggest sales year (something like 300k-400k vehicles, if you can believe it) was ’81, when sales fell off a cliff for ’82.
Well, for ’82, GM introduced the revised ‘DX’ block, with a whole host of improvements that largely took care of the durability issues of the earlier years. To their credit, they did stick it out with production until ’85, but the public had long lost interest.
Still baffling that the company that owned Detroit Diesel couldn’t be bothered to cobble together a decent product the first go-round in ’78. Typical GM, stealing defeat from the jaws of victory.
Weirdly, they still refused to add a water separator – I think they did for ’85, at least on some models. A baffling omission.
GM at that time was organized more like a conglomerate of separate auto makers rather than a unified company. So each division did its own thing and was rather siloed away from other divisions except when the head office made them work together. Not too surprising that Olds reinvented the wheel rather than go to DD hat in hand for a diesel.
My father owned a 1984 Chevrolet Caprice Estate wagon with the diesel engine. My dad would usually leave for work before I was up for school, but he would occasionally forget something and return home while I was a the bus stop. We could hear the diesel coming over the hill before we could see it and would always think it was the bus.
During a road trip from NC to Mississippi one summer, we got stranded in Atlanta for some repairs. I have no idea what broke, but it did give us an unscheduled day at Six Flags. 11 or 12 year old me thought it was great.
I’m pretty sure it was close to 200,000 miles when my dad sold it and bought a Nissan Stanza.
Thanks for this! I knew about the Olds diesel engine and its use in GM cars, but had no idea they put it in trucks.
“Chevy” and “engineering disaster”? Nahhhhh.
Hilarious that GM advertises both lower fuel costs per gallon and simplified maintenance as virtues of a diesel engine.
How the world has changed….
Why, has advertising become honest?
Minor nitpick… The base inline-6 was 4.1 liters, not 4.3 – 250 cubic inches. There was a 4.3 liter V-6 later on.
I could also argue with “Chevy was the first major American automaker to take a swing at a diesel truck” as Dodge offered a Diesel pickup in 1978 as well, powered by a Mitsubishi engine.
Was it Mitsubishi? I was thinking it was an Isuzu engine. My step dad had some kind of D300 quad cab with that terrible engine in it.
Definitely Mitsubishi, the 6DR5. Remember that Dodge and Mitsubishi were closely aligned in this period, with the Dodge Colt etc.
Isuzu diesels were used in some GM products like the S10 and Chevette as GM had an investment in Isuzu.
Chrysler had an investment in Mitsubishi for many years and used a variety of stuff from them.
I’ve been looking forward to this article. I’ve mentioned before that my mom owned an ’82 LeSabre with the Olds 350 diesel. It was the car I learned to drive in, only driving my dad’s Mercedes after he knew I could handle the Buick land yacht. My mom’s had head studs installed, and my dad installed a secondary fuel filtration system, and with those mods the thing was actually shockingly reliable and made it close to 200,000 miles before any major issues. It wasn’t fast, it hated passing at highway speeds, but in that big beast of a car it would routinely get over 30mpgs on the highway and usually upper 20mpgs in the city.
The one thing to note, as is the case with all older diesels, is that running it out of fuel was a nightmare scenario. It had a manual priming pump on the fuel pump, so you could prime the pump by hand if you ran it out of fuel. If memory serves, the manual priming pump had a diaphragm that dissolved if you put in any fuel additive to handle the lack of water filtration, so the one time my mom ran it out of diesel (fuel level sender died) it was a trip to a local diesel mechanic to get to the pump primed – the dealership didn’t have the tools or know-how to do it. The diesel mechanic rebuilt the priming pump, and my dad and I replaced the fuel level sender and added the additional filtration similar to ones used on diesel generators.
Great story! It’s funny how a bit of extra effort would have seen this go down so differently
Indeed. If they had just put in a decent fuel filtration system it likely would have had a very different reputation.
Not just older diesels, or even just mechanical injection diesels, or even just diesels. Don’t run any diesel out of fuel, or gas engines with high pressure direct injection or non return fuel systems.
Indeed, that’s a good point. I was thinking more limited in scope, specifically about diesels without in-tank electric fuel pumps, as you can’t prime them by running the engine on starter fluid like you can with gasoline engines with low-pressure mechanical fuel pumps.
Ah, that’s what you meant. You actually can run a diesel on starting fluid to prime it, it’s just not good for it.
A bigger issue than losing the prime between the tank and the injection pump is losing the prime between the injection pump and injectors. That’s much harder to prime up.
A mechanic once told me to never use starting fluid with a diesel engine, but normal gasoline instead. The one time i worked on a diesel (1 cyl generator), this method worked very well (priming the pump by running the engine on gasoline squirted into the air intake).
I’ve thought about this. It would be better to use a higher flash point/higher octane fuel, unless it’s so cold that it won’t work. Ether is very low flash point and so is excellent for cold starting.
Apparently that’s the reason why you shouldn’t use starter fluid / alcohol. The explosion would be very strong and also very rapid, and a diesel with its heavier components would not like that very much.
It’s probably one of these things that won’t kill your engine if you do it once, but it’s just better to use gasoline.
The biggest issue is that the explosion is early. It’s the same thing that will happen if you put 85 octane in your sportbike with 13:1 compression: the explosion will happen long before TDC and so the combustion pressure is working against the crankshaft rotation, which is awfully hard on rods and pistons.
Ethering a diesel is literally putting like 50 octane gasoline in an engine with 20:1 compression. The combustion is waaaaay too early, and that’s a bad thing. 87 octane pump gas would ignite much later and be better for the engine, and if you could get like 130 octane race gas that would be even better.
Thanks for this explanation, makes sense. I just knew that you shouldn’t use starter fluid (ether) with a diesel, but your explanation helps me understand why exactly.
College friend had a Suburban with a 6.2L smoker. Spy hunter smoke screen when you hit the throttle.
I owned a ‘79 C10 Scottsdale that originally had the Olds diesel. But, thankfully, the PO and already swapped that tire for an Olds 350 out of a W31 442. Burnouts for days. It was a beater in every sense of the word but I had a lot of fun with it.