Gas in a 6.3 litre diesel

[Guest Skinner]

I recently purchased a dream truck. A D30 Chev 5/4 ton with a 6.3 diesel with inly 27000 original miles. Love the old square bodies also have a 79 gmc it's a work in progress. Last week I did a terrible thing I accidentally put 3/4 of a tank of gas into the diesel. I drove for 60miles never realizing my error now it won't even fire how do I know if the engine is screwed 

[Matt Harwood]

It's probably not screwed, although I'm very surprised it ran for 60 miles with gasoline in the tank. If it still turns over with the starter, then the internals are probably OK. What is likely going on is that the gasoline still in the fuel system won't fire. Diesels are compression-ignition, and regular gasoline won't ignite through compression, not even at the 20:1 compression ratios in a diesel. Diesel fuel has a much lower octane rating which is why it combusts under pressure. Anyway, if you can clean out the entire fuel system and get all the gasoline out, it should be OK. You may have to re-prime the fuel pump and perhaps pull the injectors and crank it for a while until they are purged of gasoline.

 

However, if it hydro-locked because the cylinders were steadily filling up with gasoline that wouldn't ignite and remained liquid, then there might be internal damage. If the starter turns it over, you're probably OK. If it's locked up tight, it might have internal damage.

 

The good news is the diesels are incredibly tough and the simple air+fuel operation that doesn't need spark pretty much guarantees they'll run as long as there's fuel in there. All you need is the right fuel.

 

I would also change the oil, in case raw gasoline got past the rings and into the crankcase.

 

Good luck!

[Bhigdog]

Not a diesel expert but you  possibly damaged the pistons and or broke the rings. Don't ask how I know this.  I do hope Matt is correct and I'm totally wrong. Good luck. I do wish you the best. Keep us in the loop.................Bob

[Rusty_OToole]

How much fuel was in the tank when you filled it up? We used to put up to 10% gasoline in diesel fuel in very cold ( zero) weather to prevent it congealing. No harm resulted. If the fuel was more than half diesel you may get away without damage. Does the engine turn over? Does it have compression? You should drain the system and refill with diesel fuel before you try it.

 

I'm no diesel expert but believe the biggest worry is excess wear or scoring of the fuel injection pump due to lack of lubrication. The pistons, rings, and valves should be ok. They are practically the same as those in a gas engine but heavier duty or more durable.

[mike6024]

It would have an injection pump that looks like this I suppose. Seals in it could get damaged.

 

I'd do like was said, clear the fuel system of gas. Drain the tank, and add some fresh pure diesel. Disconnect the lines that go to the injectors. Turn engine over to clear injector pump of gas. That is turn the engine over to see the pump clears the gas out of itself and puts out diesel instead. Reconnect the lines to the injectors. 

 

Safety first! of course! Don't let any gas or diesel spray anywhere. Collect and direct the disconnected lines into container(s).

 

 

Is thus what it looks like? http://smclassiccars.com/chevrolet/337639-1984-cucv-chevy-d30-4x4-diesel.html

 

 

Edited December 6, 2017 by mike6024 (see edit history)

[Ivan Saxton]

Mike has most of it right, but there are other minor things that I personally would do.  To get rid of all petrol, I would also dump any fuel filter cartridge.  You can empty any fuel back into the tank before you drain it by blowing back with compressed air.    Don't throw away your mixed fuel when you drain it.   It would run very well without vapour-lock in an antique car like an early Twin Six Packard, where the big carburettor between the cylinder banks works uncomfortably close to a very hot exhaust manifold on each side.    If the engine has starting glow plugs, I would take these out.   This will allow you to put a small quantity of light oil or upper cylinder lube in each cylinder, so you can re-lubricate the bores a bit by spinning the engine without compression on the starter;  ( and also reduce the starter's effort in running clean fuel back through the system and to the injectors.)   The amount of petrol actually in the injectors will be fairly insignificant, but you can give them a little squirt of compressed air to blow anything out of the top.     Unless your engine stopped with a clang, clatter, and thump, it is unlikely to have suffered much damage in 60 miles.   Petrol should burn nicely mixed with diesel in a compression ignition engine.    In fact, it may even have given better conversion of the chemical energy of the fuel to useful power.  Most normal diesel engines cannot convert the last 18% of energy in  the fuel , and they emit semi-combustion residues in what should be a clean exhaust; even though diesels always run with an excess of oxygen above the theoretically correct mixture.   This is why a diesel gives significantly more power, better fuel economy,  and a clean, not- polluting exhaust when you provide  a controlled sniff of either Liquefied Petroleum Gas or ( stored)   Compressed Natural Gas  in the intake air  ( upstream of the turbocharger if there is one).   The engine oil also does not blacken, and you can extend the mileage between oil changes.   Several year ago I explained this gas-over-diesel to a young local earthmoving contractor. He got a local mechanic who did gas conversions on petrol vehicles to do an installation on his new turbo diesel four wheel drive.   On the chassis dynamometer it put 20% more power through the wheels with the gas switched on . Jim could not tell me what the diesel economy was, because he drove to enjoy the performance.  But the contents of the smallest LPG tank available, (five gallons)  lasted just on 1000 miles.

It could be a useful check to do a compression test while you have the glow plugs out.     If the engine will not start and run on good fresh diesel, you may need to have injector pump and injectors overhauled.

You may have some petrol in the engine oil, but not enough to cause any harm.  Oil dilution was widely and safely used to ease cold starting of piston aero engines in WW2.   Now motor racing has always been decorated by notable characters.   Now many decades ago here, one of those was  Jack Day.  Once he successfully prepared a car for a fuel economy competition.   He diluted the engine oil as much as he dared with petrol,  made the inlet valve stems a very loose fit in their guides, and drove with a very light foot and high intake vacuum.

I am always disappointed when useful threads vanish from sight because no-one responds after I have made a contribution.  I  try to be helpful technically and historically correct, and entertaining;  but no explanation is impossible to correct, improve, or clarify.   Learning is a process that continues all your life unless you allow yourself to become narrow-minded:  so I welcome differing opinions.

[Plyroadking]

If it's catastrophic I'm parting out an '85 D30 6.2L with 74k miles in Des Moines, Iowa.

[Trulyvintage]

From a practical standpoint - you can’t reverse any damage that has been done.

 

Many years ago I was driving on the I-80 turnpike & stopped at a BP station 

to fuel at one of the turnpike rest areas -  I wasn’t paying attention & topped off one of my F350 7.3 IDI Dually fuel tanks with unleaded from a green handled pump.

 

Immediately I had problems & realized what I had done - lucky there was no permanent damage.

 

60 miles is a different story .......

 

Jim

Edited December 7, 2017 by Trulyvintage (see edit history)

[Restorer32]

We've done the opposite. Accidentally put diesel in a '16 Pullman tank.

[Curti]

3 hours ago, Trulyvintage said:

From a practical standpoint - you can’t reverse any damage that has been done.

 

Many years ago I was driving on the I-80 turnpike & stopped at a BP station 

to fuel at one of the turnpike rest areas -  I wasn’t paying attention & topped off one of my F350 7.3 IDI Dually fuel tanks with unleaded from a green handled pump.

 

Immediately I had problems & realized what I had done - lucky there was no permanent damage.

 

60 miles is a different story .......

 

Jim

Back in the 90's, I did EXACTLY that on the Illinois tollway . The green handled pump fooled me.  The folks at the oasis let me out the back drive and into the neighborhood I found a regular gas station and drained the fuel.  It cost me around a hundred dollars to pay for the gas/fuel disposal.  The 6.2 GM diesel is really a gutless wonder, I should have let it die right there.  Not long after that I bought a 24V Ram, what a difference

[mike6024]

    Diesel nozzle is the one w/o the rubber boot.

[tripwire]

Mike6024,

Those boots don't appear everywhere.  Here in VT we don't use them at all and I'm sure there are plenty of other states that don't use them either.

 

WParo in VT

[Marty Roth]

I had a similar experience a few years back with my 7.3L 44 gallon diesel tank on my 2000 Excursion.

 

Being nearly out of diesel fuel, and with a full bladder, I pulled into a truck stop in Meridian, Mississippi. Deciding to multi-task, I quickly ran my credit card at the pump knowing that it would likely cut off at $100, grabbed the left-most nozzle, and made a bee-line for the restroom. Getting back to the truck/trailer just in time to hear the pump click off, and then noticed that I had pumped +/- 25 gallons of Unleaded Premium 92 octane into the 44 gallon diesel tank. One fellow suggested just adding several gallons of motor oil, another offering the advise to just add more diesel, I took the safer route to pay $100 to a local mechanic to come out with his portable equipment to pump out as much as possible from my tank, eat the additional cost of the $100 for the gasoline, and the fill the tank with nearly $200 worth of diesel fuel. Certainly a costly lesson, but better than likely ruining an otherwise good engine which wold have cost in excess of $10,000 to replace. The truck is still running strong at well over 370,000 miles, and while it may not have the punch of the newer 800+ lb torque newer models, it is functional and dependable.

 

So $400 for $200 worth, and a couple of hours lost time was a costly but valuable lesson. I recall that lesson with most fill-ups these days! A bit older, and hopefully a bit wiser...

[Larry Schramm]

3 hours ago, mike6024 said:

    Diesel nozzle is the one w/o the rubber boot.

 

Not always the case.  Depends on where you live.  Some places have the rubber boot on all fuel nozzles.