Injector pop testing videos

pcatterall

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I had 8 Perkins 4108 injectors to test so bought a cheap 'pop tester'.
It seems to work OK though I have only tested one so far. The injector 'popped' at 1800 lbs/" against what I read should be 2200. I have reservations about the accuracy of the gauge so I will test them all before thinking about adjusting any.

I looked on line to see how the 'experts' were using these devices... quite amusing ( or scary even!)… The most cautious was completely masked up, heavy gloves, spraying into a sealed container etc. It went down hill from there to finish with a French guy pumping away with one hand and holding a cigarette lighter to atomised spray … no gloves, fuel in an unsealed basin slopping over etc !! ( I think its called 'pop tester as flame thrower') I am not sure whose example I should follow !!?
 

Spyro

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If you have a local diesel specialist they are usually incredibly cheap by marine standards. I had 2 tested and adjusted and they were £12 for the pair.
 

black mercury

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Yes, if you hold a flame in front of the injector while testing it will turn into a flame thrower, but only for a fraction of a second, unless you keep pumping! About your pressures, if the injectors haven't been looked at for a few years you will get lower readings. The pressures will drop as the engine hours mount up, so what you are seeing could be accurate.
 

pcatterall

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Yes, if you hold a flame in front of the injector while testing it will turn into a flame thrower, but only for a fraction of a second, unless you keep pumping! About your pressures, if the injectors haven't been looked at for a few years you will get lower readings. The pressures will drop as the engine hours mount up, so what you are seeing could be accurate.

My 'reading up' about testing injectors has been quite interesting (and possibly useful!) As on many technical subjects separating fact from fiction is required. There seems to be a general feeling that as long as the engine works OK then the injectors should be fine but there is a view that although they work they may not be delivering optimum performance or start well.
There was a demo where 50 injectors had been removed from high mileage working Mercs. Only 5 met the requirements others dribbled, sprayed sideways or just sprayed non atomized fuel.
I'm beginning to think that after a good mileage ( or hours run) then a check on the injectors could be worthwhile ?

I am assuming that my 4108 injectors are designed to operate best at the required 2200 lbs/" as required by the 4108, I guess that over long use the spring will weaken and the injector crack at lower pressures. It will be interesting to know what the result in terms of performance would be if I were to just put them back opening at the currently indicated 1800 lbs/"

It has not been so easy to find someone locally who will test 'mechanical' rather than 'common rail' injectors and the quoted cost has been £10 each. I feel that investing in a bit of simple kit ( similar to that used by many small garages) has been worthwhile. If I do need to adjust the pressure opening setting then I can test them as often as I like.

Thanks everyone.
 

Heckler

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My 'reading up' about testing injectors has been quite interesting (and possibly useful!) As on many technical subjects separating fact from fiction is required. There seems to be a general feeling that as long as the engine works OK then the injectors should be fine but there is a view that although they work they may not be delivering optimum performance or start well.
There was a demo where 50 injectors had been removed from high mileage working Mercs. Only 5 met the requirements others dribbled, sprayed sideways or just sprayed non atomized fuel.
I'm beginning to think that after a good mileage ( or hours run) then a check on the injectors could be worthwhile ?

I am assuming that my 4108 injectors are designed to operate best at the required 2200 lbs/" as required by the 4108, I guess that over long use the spring will weaken and the injector crack at lower pressures. It will be interesting to know what the result in terms of performance would be if I were to just put them back opening at the currently indicated 1800 lbs/"

It has not been so easy to find someone locally who will test 'mechanical' rather than 'common rail' injectors and the quoted cost has been £10 each. I feel that investing in a bit of simple kit ( similar to that used by many small garages) has been worthwhile. If I do need to adjust the pressure opening setting then I can test them as often as I like.

Thanks everyone.

Peter
I used to do the injectors in the workshop I worked in in the 70s. An aluminium bowl under the injector was all we ever used. A set of prickers and brass wire brushes to clean the nozzle holes the tools. We used to use brasso and rouge powder to occassionaly attempt to lap the nozzle needle.
 

black mercury

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My 'reading up' about testing injectors has been quite interesting (and possibly useful!) As on many technical subjects separating fact from fiction is required. There seems to be a general feeling that as long as the engine works OK then the injectors should be fine but there is a view that although they work they may not be delivering optimum performance or start well.
There was a demo where 50 injectors had been removed from high mileage working Mercs. Only 5 met the requirements others dribbled, sprayed sideways or just sprayed non atomized fuel.
I'm beginning to think that after a good mileage ( or hours run) then a check on the injectors could be worthwhile ?

I am assuming that my 4108 injectors are designed to operate best at the required 2200 lbs/" as required by the 4108, I guess that over long use the spring will weaken and the injector crack at lower pressures. It will be interesting to know what the result in terms of performance would be if I were to just put them back opening at the currently indicated 1800 lbs/"

You would see a slight increase in efficiency, but you probably wouldn't notice it, and possibly a slight decrease in smoke, again you probably wouldn't notice on your engine. Still worthwhile doing, especially as it won't cost you anything. Your injectors are easily adjusted, most others are adjusted by shims so you would need a shim set for those. It is just wear through the whole injector, not really the spring. Indecently when new nozzles are fitted the pressure is set 5 bar above normal, it will drop by 5 bar in an hour or so as the new nozzle beds in. Some engine manufacturers specify the injectors be tested every 1000 hrs. Yes it is worth while doing because if you don't and the needle doesn't seat properly you will get carbon up inside of nozzle, then the nozzle will get to the stage that it needs renewed. Servicing would prevent this. As the injector wears you will notice the spray pattern getting a wider angle, known as fan tailing, or it will spit tiny droplets within the atomised spray, then it needs attention. When you test your injectors, dry the end of the nozzle with a piece of cloth and test the injector a few goes, the nozzle should remain dry, I it's wet or dripping, it needs attention. When the nozzles are wet this can cause blue smoke, especially at idle or on the overrun. A really bad injector can actually melt a piston. Or if the spray pattern is bad it can direct the fuel on to the cylinder wall instead of on top of the piston in a direct injection engine, rapidly wearing the cylinder bores as the diesel dilutes the engine oil, especially if the engine does a lot if idling. The same effect can happen if you put the wrong thickness of copper washer where the injector seats in the head. Have fun with your tester, just don't put your fingers over the nozzle when you're testing them! You will blow your nail off on other side of finger! Oh and cleanliness is vital. Some caps for the top of injectors would be useful to you, it is very easy to get a spec of dirt in there when you are refitting your injectors.
 

pcatterall

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Thanks black mercury for that explanation. I need to check again using the hint that the nozzle should remain dry, I may have to do a few blasts outside the 'catchment bowl' for that as with my present set up the atomised fan splashes back from the bowl and wets the nozzle end. The fan looks right and all injectors give the same sort of pattern so that looks ok.
I'm glad I invested in the tester and thanks to what I have read and your guys advice feel that my understanding of the fuel delivery side is getting better.
 

NormanB

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Peter
I used to do the injectors in the workshop I worked in in the 70s. An aluminium bowl under the injector was all we ever used. A set of prickers and brass wire brushes to clean the nozzle holes the tools. We used to use brasso and rouge powder to occassionaly attempt to lap the nozzle needle.

+1

But be warned not only is there a flammability issue - there is also a skin penetration problem so sensible precautions all round.
 

pcatterall

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Thanks all, job done! 8 injectors tested. 1 from each of the sets of 4 was cracking at 1800lbs/" . As black mercury said the ones on the 4108 are easy to adjust, there is just the top cover to remove and the adjusting screw is revealed. In my case it was just 1/8th of a turn to get the right setting. Strangely there is no lock nut and, as there were non on any of the 8 I have to assume that this is the design.

A worthwhile task ( in my opinion) as I am confident about the injectors, have improved my knowledge on the subject and have the tools to repeat the exercise on hand.
 
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