Yanmar 3JH4E - Running on Gas

[Issywa]

I recently posted (see Plastic Diesel Fuel Tank) some comments regarding contamination issues of my diesel fuel which turned out to be 24 gallons of gas in a 33 gallon tank. Not a good story.

So here's the follow up of what happened to the engine after running it for almost 11 hours on a contaminated fuel system - apparently nothing!

After cleaning out the tank, fuel lines, filters, pulling and checking the injectors, I finally have been able to sea trial my boat. RPM's and power seem to be the same at various speeds, including my normal operating speed of ~2400 RPM or 80% of maximum. Also, at full throttle, the boat speed seems to be the same as before.

My engine has about 1000 hours on it and I was very concerned that I had caused serious damage. I did not scope the cylinder walls etc, so my above comments are based on my personal observations of the engine seeming to run as well as before. I am wondering though if I have prematurely "aged" the engine and whether I have shortened its lifespan.

In speaking with various mechanics, and other boat owners, I've heard mixed reviews ranging from "Yanmar's are very robust" to "lucky" to "you're screwed..."

Anyway, just wanted to let you folks know what the end of the story was.

[a64pilot]

The damage is most likely high wear and it will be in the fuel injection system if anywhere, gasoline has very little to no lubricative properties and the fuel system is both cooled and lubricated by fuel.
Modern ULSD has less lubricity than old fashioned Diesel, but gasoline has almost none.

Older VW Diesels had in the owners manual that in cold weather to prevent fuel gelling that you could run up to a 10% gasoline mix.

Hopefully you may have dodged a bullet, but if your pump fails you may know why. If I were going places where fuel injection shops are infrequent, I’d have the pump and injectors inspected for wear. Tell them what happened.

[slug]

Lubrication ...The fuel injector pump might have been damaged

[Wotname]

I agree that it is likely you have some increased wear in the injector pump (IP) but...

The engine has done a 1000 hours so there is already some slight wear in the IP thus the plunger and cylinder is not super tight.

Lets say there is a twenty fold increase in wear from running the gas/diesel mix. That means you have put 220 hours of additional wear on the IP. Thus the IP has a total wear of 1220 hours.

Probably not worth worrying about unless the engine shows some IP problems in the next few hundred hours (IMO).

BTW, I think the twenty fold increase in wear is at extreme end of the range.

[skipperpete]

Check the crankcase pressure, that’ll give you an idea of whats going on with the rings and liners.

[Midnight Son]

Unless some detonation events occurred, kind of likely at that percentage of gasoline in the diesel, you have Injection Pump/Injectors to worry about. Pressure test of the coolant system, for a cracked head. Leak down test of the cylinders, for ring damage, due to pressure excursions (detonation).

[Mike Banks]

Your cylinders will be OK. Gasoline engines run pure petrol, but the walls are not lubricated by the fuel. Of course diesel engines last longer because of the lubricating effects of the fuel itself--but in a sweetly running diesel engine all of that fuel is burned as soon as it enters the cylinder anyway.

If there are problems they will be in the pump--and I do think you are probably OK if it is working well now.

Incidentally, in New Zealand buses with diesel engines were run on LPG. They pressurized the fuel tanks, but drew the gas as a liquid and pumped it through the injector pumps into the engine--with a 25% diesel fuel (old diesel fuel with better lubricity that would have been) mixed in to keep the pumps lubricated.

Your mix was 60% diesel--so I think you will probably be fine.

[merlyn]

I agree with the diagnostics of our collegues. But as a professional mariner and shipwright I would urge you to consider that a boat is not a car that stalls by the road even on coastal cruising and more so in ocean cruising a motor that stops and can not be restarted can be disastrous. Consider a good mechanical shop to diagnose from the crank bearings to the top and cylinders and head. You got off easy on the first you might not get a second chance.
And wear and damage are not empirical no one can asses without measuring.

[a64pilot]

Originally Posted by Midnight Son

Unless some detonation events occurred, kind of likely at that percentage of gasoline in the diesel, you have Injection Pump/Injectors to worry about. Pressure test of the coolant system, for a cracked head. Leak down test of the cylinders, for ring damage, due to pressure excursions (detonation).

Ignition timing is controlled in a Diesel by injection timing.
Detonation occurs in a gas motor because all the fuel and air are present, then bang the whole charge goes off nearly instaneously due to compression ignition, as opposed to a steady flame progression from the spark plug.
A Diesel is almost immune to detonation as it can’t occur because the fuel isn’t present until it’s time for it to burn, and of course the injection event takes a minuscule amount of time, but it’s still not instaneous.

The rattle / knock of a cold Diesel is largely due to something similar to detonation as the ignition lags the injection cause it takes heat from compression to ignite it.

[a64pilot]

To asses crankshaft bearing etc, requires disassembly, if you go through all that trouble and expense, overhaul it and reset the clock.
However you can get a very good idea of bearing wear from oil pressure with the engine fully warmed up and at idle, compared to cold idle oil pressure.

[model 10]

Originally Posted by a64pilot

To asses crankshaft bearing etc, requires disassembly, if you go through all that trouble and expense, overhaul it and reset the clock.
However you can get a very good idea of bearing wear from oil pressure with the engine fully warmed up and at idle, compared to cold idle oil pressure.

Ha! Finally we find a good use for a one time oil sample. Low psi from bearing wear is going to be giving really high readings of bearing material.

[Midnight Son]

Originally Posted by a64pilot

Ignition timing is controlled in a Diesel by injection timing.
Detonation occurs in a gas motor because all the fuel and air are present, then bang the whole charge goes off nearly instaneously due to compression ignition, as opposed to a steady flame progression from the spark plug.
A Diesel is almost immune to detonation as it can’t occur because the fuel isn’t present until it’s time for it to burn, and of course the injection event takes a minuscule amount of time, but it’s still not instaneous.

The rattle / knock of a cold Diesel is largely due to something similar to detonation as the ignition lags the injection cause it takes heat from compression to ignite it.

A little reading:

https://oards.com/gasoline-fuel-in-d...gine-symptoms/
https://www.thoughtco.com/accidental...gasoline-85225


Have a great time on the water

[bongo]

A little while back I worked at McMurdo Station, Antarctica, in the power plant. We burned AN8, an Arctic/Antarctic fuel for diesels and gas turbines. It has little to no lubricity, as at -70 deg F it would precipitate out as paraffins and clog all of the filters/injectors. The generators were powered by CAT 3500 series Diesel engines. We did not have a problem with injector wear. We did, however have a problem with valve wear. As such, we removed the rocker arms every 1000 hours to measure for valve recision. (The valves could turn into pizza cutters before going through the turbochargers).
11 hours, some lubricity, I’d bet that you are just fine. Flush everything and run it. Keep an eye on the oil pressure of course.

[olaf hart]

It’s probably worth a sump oil analysis just for your state of mind...

[Compass790]

thanks for the follow up Issywa,
I haven't experienced that fuel problem but if your engine is running fine with no strange noises I'd just keep using it. Doubt you'll have catastrophic failure if the oil pressure & engine temps are normal.
I liked Wotnames accelerated wear analysis in injection pump. Partially guesswork yes, but well reasoned.
Relax, have a beer. Just my 2c worth