Plutoe

Once again other forums are and have been providing loads of misinformation on the testing and supposed rebuilding of electronic fuel injectors used in the OM642,646 and 648 diesel engines

They forget that supply and timing of fuel injection is not controlled within the injector but typically controlled by the engine control unit(ECU) based on design and many inputs from many sensors to provide the design quantity and timing of the fuel delivery.

Assuming that the injector is electronically sound(tested using DAS Xentry) a very popular and widely used additional test to determine correct fuel quantity/timing of the injectors is fuel flow or the leak oil test.

This test is run with the aid of the manufactures diagnostic equipment and in the MB case that would be DAS Xentry.

The test is very simple providing you have the tools, in any event every MB diesel returns an amount of unused fuel to the tank and if each injector is operating to spec will return a set amount of fuel back to the system. That set amount of return or leak for every cylinder is captured in small graduated containers-----if all the amounts are similar for a given time in the test the injectors are fine, however if you notice a much larger or smaller amount of fuel--the test indicates that the injector be changed and then coded to the cylinder.

Very simple. But once again it takes tools and diagnostic equipment, therefore that means folks charge for the service!!

http://www.ebay.com/itm/331019198309?_trksid=p2059216.m2763.l2649&ssPageName=STRK%3AMEBIDX%3AIT

mersum1es

DIY 2$ test device (few inches of hose), just remember to clamp the actuatl return hose...

josh8loop

I've used that particular return fuel test kit. Quality wise it's Harbor Freight type quality. Blow molded case, decent brass fittings, metal hook/holder for the graduated plastic bottles. I wish the clear lines were longer but these are workable. This one is certainly made in China and private labeled. paid $55 for mine and free shipping. That was the most I was willing to pay for something I didn't absolutely need. At least I have some numbers to compare future readings with



I ran 3 tests and ran the engine until one of the bottles reached the 10mL mark. In my case it took around 6 minutes and 10 seconds at idle to do this. Here are the results:

Cylinder #

#1: 10mL
#2: 8.5mL
#3: 10mL
#4: 8mL
#5: 8.75mL
#6: 9mL


All three tests came out to within .25mL of each other-close enough to call all 3 tests exactly the same. Maximum deviation on Bosch injectors is 3x the lowest value recorded. In my case the max back leakage of a single injector can approach 24mL and still be considered serviceable. Mine have at most a 20% deviation which is far less than the 300% maximum.



Hope this helps get some numbers out there so others can compare for a baseline.