No they’re not! I once put the nozzle for the diesel pump in the filler tube of my Mum’s (petrol) Civic, I wondered why the nozzle wouldn’t fit in and then saw the colour of the handle on the pump. Possibly it may have been that low sulphur stuff Tesco’s and other stations deliver, yellow on the pump and handle. Embarrassing, but not as much as it would have been if I’d pulled on the handle regardless :o
BTW, this was from the pumps for cars, not the lorry pumps to one side.
I have heard that most filling stations have had cases of petrol cars being filled up with diesel ,as well as the other way round. Here is one actual case
I took an old Volvo PV144 to Stockholm (to see Leonard Cohen) like this one:
In the first photo
On the return journey, mistakenly refuelled with diesel, full tank too.
It ran as well on deisel as petrol but provided a wonderfull smokescreen that would have hidden an aircraft carrier, 200 miles. Good job the roads were quiet.
Refilled with petrol and all was fine again, car returned to the barn it had stood in for fifteen years.
This made something go “click” in my head. Years ago I read in a bound compilation of some wartime magazine an article in which the writer complained about a tractor chugging away in the village marketplace and wasting about twenty minutes’ worth of fuel, instead of stopping and restarting. It makes much more sense now as to why the driver did that: not simple idleness, but that the saving would be small in view of having to run for a few minutes on expensive petrol just to stop, and again (which I knew) to restart, whereas leaving it idling just burnt some cheap paraffin (which is almost certainly what it was burning).
My Dad used to have (almost certainly still does have; you’ll find his picture in the dictionary next to the word “packrat”, dearly though I love him) a paraffin-burning blowlamp. Similar story, except it had a little well to be filled with meths (wood alcohol) in order to light it, as you had to get the fuel to vapourise. Once up and running, it was self-sustaining and made a nice hot blue flame, without being as much of a bomb waiting to happen as a petrol-burner would have been.
[nitpick] You linked to a pic of a PV444[/nitpick] 
Yes if you did not have too much diesel in the tank, you could have the car still run and fog for mosquitos. but if you did not have enough gas in the tank, the diesel would not burn.
Let me tell you about one of the worst days I ever had as a technician. My boss gives me a repair for a P1800 that says No Start. I ask him about it and he says that the customer came out one morning and the car just would not start.
I go to the car, it cranks, it fires up and dies right away. This is weird, because if a car starts it usually stays running.
Anyway I start checking things. This car is a roach and everything I check is FUBAR, the plugs are wet and don’t look like they have been changed in a zillion miles, only one side of the injection trigger points is opening, the ignition points are pitted, the cap, rotor and wires are all bad. I have no clue how long it has been since this car saw the inside of the shop, but lord, everything I looked at was bad and could have caused the no start. Replace everything. Car still won’t start.
Pull the fuel line off the cold start injector, and pump some fuel into a bottle. No water (what I expected) and smelled like gas. Checked fuel pressure, OK. Replace the fuel line and now the car REALLY doesn’t want to start. Crank it just a few times and the plugs are fouled. After about 4 hours of beating my head against a wall and getting nowhere in one hell of a hurry, I decide to go home and try again in the AM (It didn’t help that this car was about 17 years old and had an injection system that I had never worked on before)
Anyway as I am locking up my tools, I look over at my fuel sample sitting in the soda bottle. The light from the setting sun was shinning through it and it looked straw colored. That’s strange, I thought, that does not look like gas. I smelled it again, yup it smells like gas, but held up to the light it does not look like gas.
So I cleared off a small space on my work bench and spilled some. I put a match to it. It burned for a moment, and went out! Leaving a large puddle of, you guessed it, diesel!
Well know I knew what was wrong. Drained the tank, flushed the system, changed the fuel filter, cleaned the new plugs, and guess what? The car ran like it had just had a major tune up (It had!)
So I went back to my boss and told him to get the real story. After actually asking the customer what happened instead of guessing, the story is that he stopped in a gas station, a non English speaking attendant filled his tank. He drove away the car started running worse and worse, and finally quit.
:smack: Did I mention my boss was a :wally ? If I had had the straight story in the first place, I would have had the problem isolated in 2 minutes. Instead I worked about 5 hours and got paid just for what I replaced (about 2 hours worth of labor) so I took it in the shorts for 3 hours just because that :wally lied to me. GRRR!
The reason that I didn’t find the mis-fueling when I took the sample is that the cold start injector only runs for a second when starting. That line was still a good portion gas with just a little diesel. I would start to crank the engine, the cold start injector would squirt, the engine would fire up, the cold start injector would shut off, the engine would die. After I took my fuel sample, the cold start injector had only diesel to squirt, and guess what that’s when the car really did not want to start. That is why the longer I worked on that car the less it seemed like it wanted to run.
So my comments about mis-fueling come from experience. The problem with have experience as a teacher is that you get the punishment before you get the lesson. 
Just 99.9 cents, actually. The smallest monetary unit that it is legal to trade in is the mill, which is .1 cent.
That’s some very interesting information. Thank you, and welcome to the SDMB, WeirdDeere!
Quite right Rick.
I plead haste and stupidity in a lethal combination.
The 144 was our works-wagon at the time.
Re: the paraffin burners, my dad had a salmon coble that had a petrol-started paraffin burning motor, used to scare me to death when I had to fire it up.
Minor correction to myself, the engine had to be hot to burn efficiently and to avoid too much crankcase oil dilution. It could be run colder, but that wasn’t a good idea. Kerosene was so hard to burn that fuel would slowly end up in the engine oil. At specified intervals, EXCESS oil had to be drained off, and replaced wtih fresh oil. Eventually all the oil would be drained and replaced.
Now only if I actually knew enough to contribute to these boards more often! :o
WeirdDeere
A friend of mine has one of these, and I’ve used it several times. If the air temperature is between somewhere around 40-70 degrees you only have to start it and run it on gas for 20 to 30 seconds or so, then switch it to deisel. It runs really shitty on gasoline… It’s barely enought to keep it running, but after switching it over to deisel it runs perfect. It’s a 1940’s something cat by the way.
Would burning liquefied zombies qualify as biodiesel? 
Banned liquefied zombies.
Seems reasonable. Most fuel-injected cars prime the fuel pump when you turn the key to the first or second position (before start), but if you unlock the door, it’s a pretty good assumption that you’re going to start the car. Perhaps they needed more time for the system to come up to pressure or do some diagnostic checks for some reason, and this allowed for that. They have some sort of timer so that it doesn’t bother priming the system every time if you are locking and unlocking the doors repeatedly for some reason – so it’s not really much extra wear on the pump or anything…only on the times when you unlock the door and then DON’T start the car in the next x number of minutes. Then again, the key method primes the pump if you want to turn the key on without starting the car (radio, etc.), so it’s probably a wash.
Anyone else like the irony of an OP named Otto asking question that involve fuel types and engine cycles?
I see whats going on…
That is pretty funny. What’s next, a guy named Wankel asking how a rotary engine works?
that caught my eye immediately before i read the message, then i noticed also a banned zombie.
Isn’t the Ottoban a road in Germany?
A spark plug can ignite Diesel. As a kid we had a John Deere tractor. It was a spark ignition engine. It was designed to start on gas and after the engine was worm to be switched to diesel. The carb and timming had to be adjusted if it was to be run on gas only.
Also in a spark ignition engine all the fuel is pulled into the cylinder on the intake stroke and cmpressed with the air. On a compression ignition engine only air is pulled in on the intake stroke and the fuel is injected at or near TDC causing the ignition and is injected over part of the power stroke.
I can only speak from my experience with our family’s D6. It had a separate gasoline ‘pony’ engine that was used to turn over the primary diesel engine. Once the diesel was running, you disengaged the starter and shut down the starter. It was actually a quite involved process. You can watch it here.