Would it be a good idea to replace the little spring in the fuel injector every 100k or 200k miles or at some regular interval? It seems like the metal in the spring would fatigue after a certain point.

Harvey S.

There should be no need to replace the spring. But, you are right about it changing the opening pressure over time.

We have always rebuilt our own injectors by installing new nozzles and setting up the opening pressures with larger shims. Most injectors loose 2-300psi opening pressure over 100k miles.

As long as the shim size is available it is not necessary to replace the springs.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

Hi Steve,
I assume since you are rebuilding the injectors yourself you have had bad experience with buying rebuilt injectors. I had a bad experiance when we, (me and my dad) rebuilt my moms 300td. We decided to replace the injectors since their pressure was out of spec. We got rebuilt injectors. Some of the rebuilt injectors were leaking and a few were under the specified opening pressure. When we exchanged 3 of them, one of the newer injectors still leaked a little bit. Since then I got a box full of bad injectors from a friend. The springs and shims are good in them. I have had to service one injector on my 300d and this time I did it myself. Since the nozle was good I just shimed the spring. The injector sprayed like new after that.
I would like to let everyone know that if you need to get injectors serviced, take them to a shop that knows what they are doing. Otherwise you are just throwing money away.

Mark.