Author Topic: Injectors and crappy fuel  (Read 5258 times)

starfire

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Injectors and crappy fuel
« on: August 06, 2016, 05:24:25 AM »
Lately I have been" blessed" with receiving really crappy thick and scuzzy waste oil. Its free, so i grab it anyway, we cannot be choosy when it comes to free stuff, we are in mid winter here and its all I can get. Lister has been a tad prima donnaish about burning it, shes getting a bit fussy in her old age and really wants to retire. The problem eventually was tracked to the injector, it needed a small mod to cope with the much  higher viscosity, made worse by the abnormally cold weather.
I dont know how many of you have actually had these things apart.... the experts of all things diesel would have you believe they are highly complex and shouldnt be fiddled with.
Not true.
Inside the actual nozzle is a small needle valve, this is preloaded with a spring and the adjustment screw exiting from the top of the main body. This pingle valve is designed to seal against the seat, and to lift once the fuel pressure exceeds the spring pretension, thereby squirting the pressurized fuel into the combustion chamber.
After careful measuring, i figured this valve was slightly too long to lift enough to allow the higher viscosity oil through in a sufficient quantity, in effect it was hitting the main body way too soon, it should not hit the main body at all.. The larger diameter body of the pingle where it meets with the parallel "pin" needs to be shortened by at least .5mm, easily done by chucking it in the drill press, and carefully grinding it back slightly with a Dremel tool and small grinding disk. The actual amount is really not so important, as when burning diesel it will simply revert  back to its normal opening.... its just not quite enough unmodded to cope with alternative fuel, especially when cold, thereby starving the engine. This has now been running for a few months with no problems.......
These too are very simple to adjust once reassembled.
With the engine running and under a heavy constant load, adjust the injector while watching the fuel pump rack. A point will be found where the rack will be at its minimum position, ie, furtherest back from wide open. This adjustment on mine is not critical, several turns either way from the best setting will not alter performance. This is actually a very accurate way to do this, as obviously the best spray pattern for that particular engine burning that particular fuel will automatically result in the best power output.... we are basically letting the engine tell you when its most happy.

starfire

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Re: Injectors and crappy fuel
« Reply #1 on: August 07, 2016, 05:38:14 AM »
Glort, i can see you are an old hand at this!! Thank you for the info and your experience with your fueling knowlege. Part of my reluctance to mess too much with improving the fuel is pride really.  I have always promoted self generation of power, and probably exaggerate the ease of doing it to anyone who turns up and  shows any  interest. The last thing I need is to have someone catch me covered in black shitty oil, it would always be the one person who I told weeks before how little effort is really required....... its like noone will visit soon after  you clean your untidy house, its always the day before......
Yes, I too have tried the preheat trick, makes little difference and causes all sorts of additional problems with blocked heater pipes and blockages. I have ended up with a water trap, this gets rid of the antifreeze in old engine oil, the main filtering uses horse hair wadding, the oil passing through at a slow rate leaves the crap behind, and any particles of metal, carbon etc get stuck in the weave. I did try a long plastic tube full of toilet rolls, this works but is just too slow. Tried floating the oil on water, foolishly thinking the crap will drop to the bottom, it wont and it doesnt, an old cream separator as a  centrifuge, not really useful, but the idea is sound. Settling tanks are definitely a good idea, but im getting too old to hump 44 gallon drums around these days.  Its amazing how clean old oil can get.... check this out..

https://www.youtube.com/watch?v=zrv78nG9R04




« Last Edit: August 07, 2016, 05:54:43 AM by starfire »

Dieselsmoker

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Re: Injectors and crappy fuel
« Reply #2 on: August 10, 2016, 01:02:17 PM »
................ Its amazing how clean old oil can get.... check this out..

https://www.youtube.com/watch?v=zrv78nG9R04

NOOOOOOOOOOOOOOOOOOOOOOOOOO!!!!!  ??? :-X
That is revolting, repellent, repulsive, sickening, nauseating, stomach-churning, stomach-turning, off-putting, unpalatable, distasteful, foul, nasty, vomitous; yucky, icky, gross!!!!!!!!!!
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oldgoat

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Re: Injectors and crappy fuel
« Reply #3 on: August 10, 2016, 02:36:07 PM »
I would check the injector on a test pump before i replaced it in the head. Although you may be able to adjust it for optimum running by checking the rack opening it you don't know the the leakdown rate or the spray pattern while it is in the head. With an old pintle nozzle it could be recessed and you are just compensating for the wear by the modifications you have done.

EdDee

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Re: Injectors and crappy fuel
« Reply #4 on: August 10, 2016, 04:26:57 PM »
@all

Re the video clip..... I would rather fry my 'taters in my cr@ppy sump-gunk..... At least I KNOW there is no stewed sh!t in it....

Gross!!

Ed
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starfire

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Re: Injectors and crappy fuel
« Reply #5 on: August 15, 2016, 02:26:22 AM »
I would check the injector on a test pump before i replaced it in the head. Although you may be able to adjust it for optimum running by checking the rack opening it you don't know the the leakdown rate or the spray pattern while it is in the head. With an old pintle nozzle it could be recessed and you are just compensating for the wear by the modifications you have done.

Thing is, we can never know what the spray pattern looks like inside the engine. Squirting it into the atmosphere is easy to do, just connect the injector  to the fuel pipe while it points away from the engine and crank. Sure, you can see it misting, but remember its not dealing with or squirting against  compression, being in the open air. This is what I did, set it up till it looked right, installed it, but then  the engine became  very hard to start. Adjusting  it with engine running seemed  the best way to get this right. Removing it again from the head and looking  at the spray pattern without altering its adjustment , it looked pretty much the same to me. Im wondering if a fine mist, as you would assume to be best, is not capable of penetrating into the void, but less misted  and bigger drops do?
 I think what alters it too is the fuel viscosity. The pump forces the fuel against the pingle, this opens allowing the fuel through to the small nozzle. Having thicker fuel is the same as having a smaller nozzle in regard to flow rate. Therefore it seems to me the pressure must increase to force the same amount of fuel through over the same amount of time. This means the pingle will see a higher pressure, and will raise higher off the seat. If it cannot do this, then the flow is reduced and the squirt will take up more of the expansion stroke to complete, maybe even into the exhaust cycle.....the pump will lose control and timing will change, remembering the squirt will continue until the pressure drops. I have tried to measure injector pressure but failed.... we are possibly looking at 1000psi or more.... its could even get higher with using "thicker" fuel. I do know that when using thinner ATF, I get the familiar scritch sound from the injector when cranking, with oil, no sound at all other than the fuel pipe throbbing under the pressure, to me indicating the pressure remains much higher and not allowing the pingle to vibrate open and closed as the pressure releases between openings. However, theory aside, the mod has worked as expected.

starfire

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Re: Injectors and crappy fuel
« Reply #6 on: August 15, 2016, 02:31:11 AM »
................ Its amazing how clean old oil can get.... check this out..

https://www.youtube.com/watch?v=zrv78nG9R04

NOOOOOOOOOOOOOOOOOOOOOOOOOO!!!!!  ??? :-X
That is revolting, repellent, repulsive, sickening, nauseating, stomach-churning, stomach-turning, off-putting, unpalatable, distasteful, foul, nasty, vomitous; yucky, icky, gross!!!!!!!!!!

Toughen up...... you are too soft and fussy...... ::)

oldgoat

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Re: Injectors and crappy fuel
« Reply #7 on: August 16, 2016, 11:42:25 AM »
Your theory of a very fine mist not being effective in some cases is true. The pop pressure of the injector is a compromise between the extremes of big drops and small drops and depends on the design of the combustion space. This is decided by the manufacturer and although they use sophisticated instruments I guess the result is the same as you are doing minimum smoke and minimum rack opening for the horsepower developed.