mistake by nephew

[ups651192]

my nephew accindently pumped about 8 gallons of unleaded regular gasoline into his moms 99 VW jetta diesel, could use some advice on weather to try and pump it out or just what to do at this time, car has not been driven they had it towed and was wondering should we siphon it out just some help would be appreciated

 

[richdubbya]

Definitely do not start the engine. Siphon as much as possible out, then check, most VW's have a drain plug on the fuel tank. Drain the rest out. Dont do this work in an enclosed area and do not use a drop light or any electrical tool. The remaining cup or so of gas will be ok if mixed with a full tank of diesel so tow it back and fill it before starting. If he tried to start it with gas, then someone with diesel experience can help you bleed the injection system. good luck

 

[icrman]

All you should need to do is drain it. Refuel it and go.
Gasoline is a low cetane fuel. Actually there are multifuel diesel engines that will run on gasoline just fine. There is a lot of misunderstanding when it comes to this subject.

 

[patprimmer]

Petrol is actually higher octane than Diesel, so it might be harder to start, but detonation will not be a problem as diesels actually run on detonation. Note they have no spark plug.

The durability problems care due to the lack of lubrication for the high pressure injection pump.

Follow the previous advice about safe draining of the system. Don't bother purging it, as it is an unnecessary expense. Don't bother towing it, but get some diesel in a drum, say 20 litres or 5 gallons, add it to the tank and drive slowly to the nearest bowser.

Ensure the nephew is inconvenienced by this, so he will know not to do it again.

Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[sailoday28]

patprimmer (Automotive) Nov 28, 2004 states "Petrol is actually higher octane than Diesel, so it might be harder to start, but detonation will not be a problem as diesels actually run on detonation."

I always thought that the Diesel engine ran by combustion, NOT detonation.

 

[ivymike]

Um, what definition of combustion isn't inclusive of detonation, as the terms apply to an internal combustion engine?

What Pat was saying, I believe, is that diesel engines are compression-ignited rather than spark-ignited, and that the combustion is controlled by the amount of fuel injected and the injection timings, so the destructive knock (detonation) that occurs in a gasoline engine is not a concern for a diesel.

What's a bowser?

 

[TOHCan]

My take on combustion is a controlled burn that is initiated at a specific point in the combustion chamber and progresses through the chamber with a single flame front. This would apply to both diesel and gas, with the obvious spark for gas, and the diesel having the fuel ignite as it contacts the high temp compressed air in the chamber. Detonation occurs when a combination of high temp and high pressure causes spontaneous ignition of a fuel-air mix. This can occur in both types of engines, and neither like uncontrolled combustion. Pre-ignition is caused by a local hot spot that fires the mixture at some point before the normal time as the engine is completing the compression stroke, as the name implies.

 

[evelrod]

I am no diesel expert but, I can say that destructive detonation does occur in a diesel engine under the right (wrong?) circumstances. I was at a tractor pull in Anaheim a few years back and witnessed such an event. The diesel engine "sound" changes dramatically in detonation and, in just a few seconds, turned the engine into a bomb. Quite spectacular---quite dangerous for the spectators in the close up seats. Part of the cyl. head must have gone up at least 100 feet! We were in the third tier and it was "eyeball level" with us!

Yeah, Pat. What's a bowser?

Rod

 

[ivymike]

My take on combustion is a controlled burn...spontaneous ignition of a fuel-air mix

Nah, combustion is the reaction of the fuel with the air, regardless of when it happens in the cycle, or why it happens.

http://www.m-w.com/cgi-bin/dictionary?book=Dictionary&va=combustion

1 : an act or instance of burning
2 : a usually rapid chemical process (as oxidation) that produces heat and usually light; also : a slower oxidation (as in the body)

 

[TOHCan]

I was meaning to clarify the difference between what is commonly referred to as combustion and detonation, and added the other term that gets mixed up in the fray. I should have added controlled or desirable as a qualifier. Sorry!

 

[zeusfaber]

Bowser: Tanker used for refuelling (often aircraft) directly.

A.

 

[GregLocock]

Well, fair enough. It's also that tin thing in the middle of a servo's forecourt that 4WDers drive into on a regular basis.



Cheers

Greg Locock

 

[ivymike]

Californese: a fuel pump at a gas station?

 

[patprimmer]

Isaac and Rod

A fuel pump at a gas station would be a suitable translation, or a device for refuelling vehicles at a gas station, normally involving a trigger to control flow and a metre to determine cost, or even a tin thing as Greg suggests.

Getting back to the original question, despite any controversy over the definitions of combustion and detonation, I still say that petrol is higher octane than diesel fuel, and will be less inclined to ignite due to compression of the air in the cylinder, therefore a little in the diesel fuel will do no damage in a short low load trip.

If someone wants to continue about the rate of combustion of different fuels in a compression ignition engine, maybe they should, first do a site search, then start another thread on that subject.



Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[icrman]

You are correct Pat. Gasoline is high octane, Diesel is low Octane. Gasoline is low Cetane and Diesel is high Cetane.
The knocking noise in a diesel engine at idle, has been called "cetane knock". And correct again about detonation in a diesel engine. The lower the cetane the fuel the more the engine would tend to knock. And with a slow flame front, like in a gas engine the unburned fractions explode under the heat and pressure. This happens even with good average cetane diesel fuel, on a modern engines.
A diesel engine will run on straight average gasoline, there are many brands of Multifuel diesel engines.