1985 300TD Severe Injector Knocking

Hi all,
About two weeks ago we rebuilt the injectors for the 85 300td. Popped them in, and they worked great. there was still a small nailing sound but throttle performance was restored and car was much happier. However, they leaked pretty badly between both halves. So, out they came tonight, we re-lapped them (we didn[t look at kent's pictures very closely the first time, second time we did it by the book with the process.) We used brake-cleen to clean the parts throughly including the nozzle and inside of the injector housing. The car now stumbles, seemingly barely running at idle, and is knocking terribly. We though it was the brake-kleen we used to clean them, but hooked up to diesel purge car ran fine. Back on diesel though, and it ran like crap. Ideas?

Forums

Diesel Engine Specific Aid

Chassis Model Number

W123

Clarification needed

Hi Nathan. I need a little more info to help you narrow this down. Did you use a pressure tester to set injector release pressures? Did you use a torque wrench? Did you attempt to tighten the injector halves a little extra to stop the leaks? Thanks. Kent

Used your pressure tester,

Used your pressure tester, shimmed them up really nice to about 1950 and 2000 on each one (as accurate as we could get). Used torque wrench at 60lbs on the first try, lapped them and did 70lbs on the second batch. Also used 60lbs on engine block

problem solved

Kent,
We could not bare to drive the car like that so we started cracking hard lines with it running. When we cracked cylinder number 3, fuel and smoke spit back at us! We removed this one, took it apart, and found the nozzle had broken in two inside the casing! The nozzle was squirting with no pressure on the tester! We had the nozzles intended for the 79 and popped one in, tested all the rest just to be sure, and problem solved!

Clairification...

The nozzle needle had broken in two when tightening the first time (the wrench kind of went really tight after two turns, kind of like crossthreading, but then released and tightened normally the rest of the way so we thought all was ok), effectively leaving an open path from the IP pump to the combustion chamber.

Glad you found the problem

Good job on isolating the problem. Also, keep in mind the recommend torque must be following to the letter. We have seen problems associated with over torquing a couple of times. The nozzles are machined to exacting and very close tolerances. 59 ft pounds should be the max. Over tightening the halves can deform the nozzle holder and damage it as well as cause the needle to hang up in the holder. This results in severe nailing. We had one set come back that some "mechanic" had installed. He had so overtightened the halves in an attempt to stop the leaks that it actually caused the needles to overheat and SEIZE in the holders. If you are still experiencing any nailing this could be something to consider.

So if I remove the injectors

So if I remove the injectors and torque them to 59lbs, and they still leak, can I assume I just need to relap them? what kind of risk am I running at 70lbs?