Quote:
Originally Posted by tobybul
D911, do you think pop testing is absolutely necessary? I am thinking about getting a set of Monarks. I guess I can always try putting them in without pop testing and see if it performs properly... and if not then may be do the test.
What do you think?
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Everybody has to make their own decisions on that; I say yes it is clearly best to have them pop tested when replacing the Spray Nozzle (and also to lap the internal precision surfaces before assembly).
Maybe I can explain it a little better.
There are a couple of things that happen as injectors are used. 1- The Pintel seating area in the spray nozzle wears out and they start to dribble raw/un-atomized fuel before their set pop/opening pressure is reached. 2- The tension in the spring inside of the injectors tends to weaken with use and when tested the pop/opening pressure is after many years of use lower than spec and they are not balanced between the set of injectors.
If you know the seat in the injector Spray Nozzle the is no good (you test for this on the pop tester). You will get improvement just by changing the Spray Nozzle (Diesel Giant has a how to do; do one nozzle at a time to keep the parts together for that nozzle). But the dimensions of the new Spray Nozzle may not be the same as the old one (especially Monark vs. Bosch) and this will change the tension on the spring in the injector. Meaning that the Pop/opening pressure of the nozzle will change and they will not be balanced between the other injectors (your injectors all could have different pop pressures; maybe out of spec; no way to tell without pop testing).
The pop/opening pressure of the nozzle also has an effect on your injection timing. Lower pressure injects the fuel sooner than a higher pressure.
Depending on my fanancial situation at the time I could see myself only changing the Spray Nozzle with out pop testing if my car was running poorly.
In my case when I bought a diesel car (Volvo) in 1992 I knew the injectors neededrebuilding and I bought a cheap ($150)Chinese Pop Tester right from the start. I figured a good part of the purchasecost of the pop tester would would be saved by not having to have 6 injectors rebuilt in a shop.