Dieseling engine

[Nightjar]

Many years of experience with engines have witnessed several diesel engines keep running backwards after shutdown until they destroyed themselves.
This morning after mowing the lawn the petrol mower backfired violently after shutting down, managed to pull the spark plug lead but it still kept running.
Felt sure the TRG would have rushed our place thinking there was a gun battle in progress.
Looks like a new mower is on the shopping list.
Has anyone here ever experienced a petrol engine running on/dieseling?

 

[Tathradj]

Had a turbo seal go out on a petrol engine once.

Even shutting the air intake would not stop it.

The end result was not very nice. :awful: :8

 

[Sandta]

Carbon build up in cylinder acting as a glow/spark plug

 

[rustyhooks]

I n my dim past in the early seventies i started a lister diesel gen set on a frinds station in the Pilbara and it bouced backwards and almost stuffed up there switch board in the shed as the bloody lister decided to fire up in reverse , exhaust coming out of the air filter throwing oil every where, hahahaha the owner was not impressed as you could imagine.

 

[Mike678]

I have seen a motor mechanic give a petrol car engine a quick de - coke . Take the air filter off , load an oilcan with kero . Have the engine running with some speed, 50 % ? and then squirt kero in . Watch the coke go out the tail pipe !

 

[Tathradj]

75 % water
25 % Auto Transmission Fluid.

About 2 cups.

1 x petrol engine with about 250,000 city driving on it.

Start and warm the engine up to operating temperature,

Slowly pour, About a teaspoon full a time down the inlet port.

Keep it revving and be amazed at the amount of smoke generated.

When you run out of fluid,

Put it back together and go drive it like you stole it.

Finally, Be amazed finally at the difference it makes.

Do an oil change then go about your normal daily driving.

 

[Jaros]

Do you think that would some effect on a car that has driven 95% of it's life on LPG?

 

[Nightjar]

I n my dim past in the early seventies i started a lister diesel gen set on a frinds station in the Pilbara and it bouced backwards and almost stuffed up there switch board in the shed as the bloody lister decided to fire up in reverse , exhaust coming out of the air filter throwing oil every where, hahahaha the owner was not impressed as you could imagine.

The diesels that I've seen destroyed were Caterpillar and GM rigged up to air compressors for drill rigs boring blast holes.
When they ran in reverse it was exactly as you have described, smoke billowing out of the aircleaner.
When the sump was sucked dry of oil needless to say they died with a bang from running out of lubricating oil.
The most common result was a conrod through the side of the block.

 

[Sandta]

If its on LPG id imagine it would be clean as a whistle

 

[Jaros]

Still got tons of grunt with petrol on. Great for going uphills. It's only done just over 127,000klms. 17yr old Pathy.

 

[Guest]

G'day

I have seen small petrol engines over speed a few times, all small four stroke have a governor system so if it fails the engine will over rev but usually you can shut them down by the normal cut out switch or whatever, if your mower has a two stroke engine say like a Victa with the 2 stroke power torque motor then if a crank case oil seal goes it will intake air through there and just speed up to a frightening rate, as you cant stop it as long as its getting fuel out of the carby float chamber, even pulling the spark plug lead will not stop it, all you can do is turn the fuel off and hope it stays together until the fuel runs out.

The other thing that can happen causing the motor to run erratically is a sheared flywheel key, even a partial shear of the key will alter the engine timing and cause either kick back or run on, also with lawnmowers they can sheer the key on the lower shaft for the blade plate boss causing it to kick back as you try to start it, the weight of the blade plate works as a counter weight for the engine as well and they dont like to run without the load, a whisker of carbon or dirt on the spark plug terminal may cause the plug to misfire and then cause the engine to back fire, this is usually what causes the aluminium flywheel key to shear or partially shear jamming the flywheel out of its correct timing position.

Some lawnmower blade bosses are cast aluminium with a fixed locating key, these are designed to shear if you run over the water metre or whatever so it does not cause damage to the engine output shaft or internals, steel keys will also shear if you hit something hard enough.

cheers

stayyerAU

 

[aussiefarmer]

Grew up with a rv 90 motorbike big fat wheels was like riding a pig, when it got hot the slide in the carby would stick wide open , turn it off , pull spark plug wire and it just keep revving harder and harder, had to put it in 3rd or 4th with brakes on and stall it. It done that 4 or 5 times never detonated but should :awful: :fire: have revving like a rotory.

 

[Black-Pete]

Nightjar, back in the late 70's I had a old landcruiser petrol come into the workshop that the owner said was hard to start. After turning it over on the battery for about 20 seconds I turned the key back to just the ignition on and it ran backwards for about 30 seconds. It did this 3 times before I was worried about the oil system being sucked dry of oil. It turned out to be the condenser was faulty. Changed that and all was good.
Black-Pete