03 Mercedes SL55. Voltage on the injectors w/ key in ON p...

Welcome to JustAnswer. Thank you for contacting us for assistance with your vehicle. I'm Pete. I will be happy to assist you with your question. May I ask to whom I have the pleasure of speaking with today?

Hi Pete, I'm Ben. Thanks for your help on this.

Hello Ben. Nice to hear from you today! I'm sorry to hear you are having this problem. I know this can be frustrating. Is the vehicle starting and running properly with this issue?

No, it started w/ a heavy white smoke out of the [exhaust](/topics-exhaust-mercedes/) pipes. Read the codes. Misfire on #6 and #7. I had couple of more successful starts after that but mostly is just a click w/ no start.

Have you tried unplugging each injector one injector at a time to see if any of the low voltage reading injectors then show the correct voltage?

No but that would be an interesting test. I think I'll give it a try. Just wondering though why would you run such a test. I thought the wiring of each injector is independent of others.

Thank you for your reply and that information as this does help me better understand the situation. Please give me one moment to type out some info for you. I’ll be right back! Thank you for holding Ben! On this model, the ground pulsed signal wire for each injector is independent of each other controlled by the engine computer. The power feed wire though is tied together on all injectors powered up by fuse 20. If you have correct voltage on one injector but low voltage on others, this can indicate a weak battery, an issue with the power feed wiring leading from the fuse to the injectors being shorted or damaged, or an issue with one of the injectors internally shorted to where it is drawing to much power. I recommend unplugging each injector one at a time to see if power comes back to normal on the other injectors when one specific injector is unplugged. If power comes back then the injector you unplugged has an internal short in it and has to be replaced. If the low voltage continues to occur I then recommend to test the battery and check the battery cables and connections for any issues as well as the wiring leading from the injectors to the fuse for any damage or shorts that need to be repaired to resolve this issue.

Thanks that was very thorough. I'll do the test. I still don't understand why only one of the injectors is giving me a higher voltage and that injector happened to be on the problematic spot (cylinder #7). Question is, am I supposed to get full battery power at all the injectors when I turn the key?

You should have full battery power at all injectors with the key on. This should be at one wire at each injector. If one of the injectors has an internal short ( as they have coils inside of them ) then it will cause voltage issues to the other injectors.

Got it. Last question before I start testing, is it not better to unplug all the injectors and test the voltage as I plug in injectors one by one? This is in reverse of what you said. I'm thinking what if I had two shot injectors. It would be hard to spot when unplugging one by one. Would you agree?

You can do it that way as well as it will work the same to help identify any faulty injectors needing to be replaced.

Great. Thanks PeteI can't rate you. Does the last comment have to be from you for me to rate the conversation? Sorry I'm new to this website.

Your welcome! Glad I could be of some help! I hope everything works out well for you! If there are any additional questions on this issue that should arise, please feel free to reply and ask! Have a great day. Thank you for choosing Just Answer for your questions!

Will do, thanks you helped a lot today

Thanks!

Test is done. Unplugged all injectors. Added one by one. After adding each injector got a reading of all other unplugged connectors. All of the connectors read around 6 volts except #7 which reads 8.8 consistently. Did the test result help at all?

Just added the wiring diagram.

Y62/y7 is the injector w/ 8.8 volts reading. How would you make sense of the diagram to go after the possible placed that I might have a damaged grounded wire?

Do you have 12 volts at fuse 20 with the injectors plugged in and the ignition on?

I'll get a reading. This troubleshooting seems to be going in the right direction. Thanks. To double check, fuse 20 is titled Diagnostic socket. Is that what it is?

I have 11.9 volts on fuse 20 and all other fuses in the same fuse box. Car has been sitting for a while so a little of voltage drop is expected.

If you remove that fuse do you lose all voltage to the injectors?

Removed fuse 20 and nothing changed. Am I looking at the right fuse?

The fuse should be located in the driver's side underhood fuse panel as shown below in the links. [https://www.dropbox.com/s/j0krxh9k1q5fsq1/frm929.pdf?dl=0](https://www.dropbox.com/s/j0krxh9k1q5fsq1/frm929.pdf?dl=0) [https://www.dropbox.com/s/21rut72qax0fc4g/frmf929.pdf?dl=0](https://www.dropbox.com/s/21rut72qax0fc4g/frmf929.pdf?dl=0)