Testing K-Jet Injectors

[Styria]

Information to be submitted at the earliest opportunity. Regards Styria

 

[6.9forever]

Eagerly awaited, Styria .....

 

[Styria]

What do we know about the injectors, being buried deep in the inlet manifold, and no convenient way of inspecting them ? The answer is very little, unless they are removed and then tested on the bench, or by way of some other means. In this case, it was by other means as a previous testing facility was no longer available, so another method had to be devised.. I also rang around to see if there were alternative sources that could carry out the tests, but those efforts came to nought. So, the question was: How do you test them ?

The initial advice was to remove an injector, presumably one at a time, start the engine and observe the spray pattern. I removed two and tried to start the engine, but really that was disastrous. The engine ran like a chuff cutter, noisily, and you just couldn't keep it running unless you had another person playing with the throttle. Highly unsatisfactory. At this stage, I should also point out that it helps to have spare fuel lines as illustrated.



Now, that is the only photo in this thread. Regarding spare fuel lines - yes, one can use the ones fitted to the car, but each line is a certain length with well defined bends and curves, in other words shapes, and fitment at each end into the injector and the fuel distributor is very precise - you just do not get those lines out of shape. Thus, the reason for the spares. In this instance, I also had some spare injectors, including new, so again it helps to have some of those on hand. Just in case, but also to enable a comparison to be made between "good", not so good or just plain unserviceable.

With those two spare lines hooked up, I fitted the first two injectors to them. You also have to disconnect the wiring loom from the switch on the inlet manifold so that one has a continuous supply of fuel when the ignition is turned on. So, having done that, in other words ignition on, wiring disconnected, injectors fitted to the lines, it is now simply a matter of pushing down the large metal "diaphragm", and the injectors will start spraying. There is obviously no need to run the engine. Just have the ignition turned on.

We now have to look at the spray pattern. It is to be strong with an even cone shaped fine "spray mist". It was quite clear that, in this initial test, there was a different spray pattern between the two injectors. One exhibited just three or four strong "squirts", with negligible mist. Clearly, faulty to some degree. The other one was fine, but I now proceeded to test all my other spare injectors, including four new ones. It did not take long to sort out the good from the bad, but I set them aside as I then proceeded to remove and test the other six injectors one at a time. Altogether, I finished up with three good original injectors which I refitted, with the rest either spraying to the side, rough "mist" and it is quite surprising that one can also test the spray pattern by the degree to which the diaphragm is pushed down. The further down, the stronger the squirting or spraying action.

The whole job, from go to whoa, took nine hours. Having done it once only, any subsequent effort can probably be reduced by, say, two hours. This is also one job where re-assembly can be achieved quicker than dismantling. Naturally, I should also point out that new rubber sealing pads were fitted. Regards Styria

 

[CraigS]

If I read this right, you have 3 good injectors, so what are you going to use for the other 5 ? Or did you clean some of the dirty ones, check the spray pattern and reinstall them ? Out of curiosity, what is the cost of new seals ?

 

[Michel]

Your ingenuity never ceases to amaze me Godfather.

Thanks for sharing

 

[Styria]

If I read this right, you have 3 good injectors, so what are you going to use for the other 5 ? Or did you clean some of the dirty ones, check the spray pattern and reinstall them ? Out of curiosity, what is the cost of new seals ?

Hi Craig, the new seals cost me $26.50. It is not possible to clean injectors on account of their internal design. Thus they have now to be discarded. I finished up using four new units, the three that were okay, plus one of the used items I had on hand. Regards Styria

N.B. I honestly cannot overemphasize the importance to have spare parts on hand - they've gotten me out of trouble more often than what I care to remember.

 

[SEL_69L]

A good injector must pass two tests:

1. Fuel flow rate,
2. spray pattern,

both at a specified fuel pressure.

 

[CraigS]

I thought you could clean them ultrasonically ? I have an ultrasonic cleaner so would be happy to try it on one or a few of your "faulty" ones.

 

[BenzBoy]

You can clean them ultrasonically - or with fluid if they don't have too much of a build up of "varnish" but they do reach a point of no return where they are corroded if they are not cleaned regularly.
The Spirit runs K Motronic and I had Bosh ultrasonically clean them with excellent results. The spray pattern of the originals was better than that of the modern equivalent. Go figure...
See - http://www.bosch.com.au/content/language1/html/4554.htm
Regards,
Brian

 

[Styria]

I thought you could clean them ultrasonically ? I have an ultrasonic cleaner so would be happy to try it on one or a few of your "faulty" ones.

Hi Craig, I would certainly like to take advantage of your kind offer. A friend of mine dissected one unit quite some while ago, but he ventured the opinion that cleaning in a normal manner would be futile and a waste of time. Plus, I have heard this from other sources as well, but I don't suggest that cleaning by means of ultra sound will not be successful. Until one tries, you just don't know. Regards Styria

 

[Styria]

Hi BenzBoy, those injectors, as illustrated, are different types of injectors to the mechanical units used in the M100 and M117/116 engines - well, at least those fitted with K-Jet injectors. I would be most interested if there was to be a Bosch facility for them to clean K-Jet units, and at what cost - if at all possible.

The Motronic units that you are referring to would appear to be electronically triggered units, probably similar to those used on D - type injection. I can understand why one would explore all possibilities to clean those on account of cost - in the case of D - type, injectors are about $200.00 each. I would imagine that the Rolls Motronic units would go well beyond that price. I have also been told (some years ago) that after market K-Jet units are "crap" - don't know why, as they are Bosch units, but that's what I have been told. Again, to use your apt expression "go figure". Regards Styria

 

[Oversize]

As an apprentice we used to remove the fuel pump relay & bridge the terminals to allow the pump to run without the ignition, or the engine cranking.... We'd also carefully remove all the injectors & bend the supply pipes just enough to observe the spray patterns. We'd need two large trays to catch the fuel spray, which was less than safe. It pays to even check the pattern of new injectors, as I've heard of them being faulty before (probably due to excessive use of anti-corrosion wax). I'd certainly give ultrasonics a go, but if it's not reliable it might be cheaper to just buy new ones.... Love your work Styria!!

 

[CraigS]

We just need to find out who these companies have sold their products to.

http://www.autohoist.com.au/process/shop/productView.html?itemId=32499

http://www.autoequipment.com.au/MAE_NEW/CARBONZAPP/CarbonZapp_A8000_A4040.htm

 

[Styria]

Well Craig, what can I say ? At the price as quoted in the first named link, that is $3850.00, it is highly unlikely that any of us would entertain such expenditure. In fact, looking at the equipment, it appears very similar to equipment as shown in one of my threads as far as 6.3 Fuel Injection pumps are concerned.

Remember, the machine is just for testing - it doesn't make or supply new units and given today's old K-Jet technology, you'd never get your money back. Sorry, I don't mean to be negative - I am sure you will understand where I am coming from. Regards Styria

 

[CraigS]

I'm not suggesting that anyone buy the equipment. I am suggesting finding out who these companies have sold the equipment to so that we can see if they are able to offer a testing and cleaning service.

 

[Styria]

Your ingenuity never ceases to amaze me Godfather.

Thanks for sharing

Thank you for your kind words, Michel. I haven't mentioned it thus far. but I can relate now that this engine is idling far smoother now. Absent is the tremor previously experienced at idle, although it is still not 100% perfect. I suspect that even when new, 6.9 engines would exhibit a slight tremor on idle.

Unless I am mistaken, I also tend to feel that acceleration is now quite a bit more brisk. Regards Styria

 

[c107]

I know this is a very old thread, but has anyone tried the test rig that Kent Bergsma sells? Given the cost of injectors, $200USD seems better than just replacing them as a matter of course.

https://mercedessource.com/store/cis-gas-fuel-injector-spray-pattern-tester-and-nozzle-cleaner

I found a video of a user in WA trying it, and it seemed ok although the video was quite short.

 

[Oversize]

Any wonder these things stuff up after 40 years!!

 

[Oversize]

Apparently some have had success back flushing the kjet injectors presumably to clean out the internal non serviceable filter. However the process may still not be cost effective vs just buying new ones.

 

[Oversize]

In fact I can’t see how you could even do that based on the design of the nozzle!!!