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Old 12-03-2015, 09:36 AM
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Join Date: May 2003
Posts: 8
Mercedes CIS injectors - Steel vs. Brass

The brass injectors with the smaller threads used on the 560, and other models are of poor design. The tips were even changed from the original steel version.
Avoid Brass Bosch 62231 or 0437502054
Order Bosch Steel 0437502035

Background story:

I finally fixed my 560SEL after years and years of different mechanics and 1000's of dollars. Years ago I had a rough idle and took it to the dealer. Of course the car was still too old for them to actually figure it out so they replaced two injectors. The rough idle never went away though; they were just throwing parts at it.

The rough idle persisted, so I replaced the other 6 injectors as a precaution. Other numerous repairs followed, the car sat for extended periods over a 5 year reign. I'm sure this was not good for the fuel system in general.

The problem seemed to worsen. When I started the car there was always a roughness, that would not go away completely, It would get better after revving the engine up really high. If I was to stop somewhere for a meal, come back out to a hot engine and start the engine would violently shake and rumble on start up.

Other times, after coasting to a stop after hard driving, and pulling away from a light, there would be a "rumble" or misfire. Drove me insane.
I replaced the fuel filter, pumps, and accumulator. No change.

The problem turned out to be the fuel injectors. The replacement brass injectors were the culprit. I never suspected them since I had replaced them previously and they were not that old. Car runs smooth as glass now. Here is what I found:

I bought the ************** injector tester and I learned a lot about testing, and determining what good injectors are.

All of the brass injectors leaked down at least 15 PSI after the valve closed. And upon reinstalling them in the car, they leaked all the way out with latent engine heat. The line and injector was completely dry when I removed them to install new steel injectors (which are cheaper than the brass btw).

I found that the brass injectors were leaking between the outer and inner casing at the bottom of the injector.

The larger thread designs used on the 190E and others may not be applicable to this problem. The brass injectors used on those models appear to have the same tip as the original steel. I will be checking my 190e very soon for confirmation.

As far as cleaning, I did not have much if any success. I have an ultra-sonic cleaner with heat and I filled it with hydrochloric acid and ran for about 15 minutes. I'm sure that some deposits were dissolved internally and the outside of the injectors were very clean but there is no way to see the inside.

Perhaps soaking longer would help? Some say cleaning cannot totally revive them and that seems to be true. For the purposes of this discussion, I won't talk about the performance of the brass injectors, because even the ones with good spray patterns still leaked down some, and others with poor spray patterns leaked a lot.

The steel injectors were more cut and dry. They either worked fine with good spray pattern, with no leakage, or they had poor spray pattern and leaked. The OEM used steel injectors that I still had popped from 58 psi up to 62 psi, and sealed completely below 58 psi. The brand new steel injectors popped at 64 psi up to 70 psi, and closed very cleanly and entirely. I have heard that it is important for smooth idle for all injectors to be within 2 psi range of each other, though I do not know from personal experience.

This is what needs to be looked at for those of us with a testing apparatus. Even without one, if you are brave enough to test on the car with raw fuel spray, you should be looking for completely and quick closing, and no leakage.

Again, from what I observed, every injector that closed entirely also had a good spray pattern.

If anyone has problems like these and has replaced the original steel injectors with brass, I would strongly encourage you to look consider what I have been through as part of troubleshooting.

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Old 12-03-2015, 07:33 PM
Senior Member
Join Date: Nov 2002
Posts: 817
steel rusts, brass doesn't, hence the change. never have seen any issues with the injectors in the mbs, volvos ferraris, etc i've seen that are brass. good luck, chuck.
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Old 12-03-2015, 08:28 PM
Registered User
Join Date: Feb 2011
Location: Modesto CA
Posts: 3,877
Not much of a surprise that the -----054 injection valve did not perform correctly in the M117 engine; it is for use in the M104 & M119 engines.

The -----035 injection valve is correct for the M116/117 aluminum block engines with KE-Jetronic.

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