97 E320 with no injector pulses
 

Hi all,

I have enjoyed this site extensively, and decided I would pose a problem that I have just come across.

I am working on a 97 E320, straight six engine - and the vehicle will not start. Fuel pump is working, and have spart at the plugs. The car cranks but will not start. Compression is good. After looking around at different things, checked to see if the fuel injectors were spraying, and found that they were not pulsing - none of them. Checked for power to the injectors and found battery positive.

I am not sure where to go at this point, as everything seems to be directed to a bad ECU. I have looked at the wiring diagrams and the injectors are grounded by the ECU.

Any help would be greatly appreciated.

ECU needs cam position sensor signal to trigger injector ground...check that.

Got any codes..that should show up....

Thanks for the suggestion. There are no codes listed when scanned. Will check the Cam sensor input to see if anything shows up.

Check this Archieves thread out too..


<<Vehicles as of 12/94 are fitted with an immobilizer stage 2. The immobilizer is now activated by the IRCL control module …. After activation of the immobilizer, the HFM-SFI control module deactivates the fuel injection system. The immobilizer can only be activated or deactivated by IRCL remote control. Opening and closing the car using the mechanical key does not affect the immobilizer….

I had the battery out of the car so I was using the mechanical key to lock and unlock it. Seems when I put the battery back in I should have locked and unlocked the car with the remote before trying to start it. It starts right up now.
>>

Tested the cam sensor and it is dead. Got another one coming. Will keep you all updated on results. Thanks for the suggestions.

Well, new cam sensor did nothing. Same symptoms - no injector pulse, so no fuel going into engine. I am thinking more and more that it is the ECU.

You are sure about spark?
No spark defaults injection on these..

Definitely spark . . . checked many times. And fuel pump activates, and has pressure. The fuel injectors are not grounding out and getting power. There is battery voltage to the injectors - which is why I am leaning more toward a faulty ECU.

Ok
What did you exactly find wrong with the first Cam sensor?

And how did you check the new one?

Hooked up a Modis and checked for signal from Cam Sensor to ECU. Got no signal. Have battery power to Cam Sensor. Did check the wire for ECU ground, and does not seem that ECU is grounding the Cam Sensor either. Cam Sensor installed was brand new. Lucky I only put it in for a few cranks, so I am going to send it back. As for checking the fuel injector pulse, I have a pulse light that I plugged into the fuel injector connector.

I really appreciate the thought and insight you have given to this problem. If worse gets to worse, may send it to Dealer and let them figure out if ECU is bad.

A few Thoughts:

There is a gap adjustment for cam sensor..possible large gap or magnet problem..
You want to see a sensor signal while cranking ..did you ohm the sensor?
My info shows cam sensor should be .8-1.5 V at crank or idle.
I don't have this schematic, but do you see a Fuel Saftey shut-off relay?

IRCL system on those cars cuts fuel in case someone breaks into car and tries to crank...make sure the remote is working..see that post I listed..that could be it...could even be the ATA fuse ...... Search IRCL......

I am with arthur on this. The drive authorization on these is a pretty common problem. Quick question, do you have the red and green lights in the mirror and doors or do you have a large ring around the ignition where the key goes in? You should have the ring, I think. Mercedes used 3 different drive auth. systems from 1996-1997, before going to the new smart key systems. If it has the ring around the ignition then locking and unlocking should not do anything.
If not then try it and make sure that you are getting an indicator for the car being unlocked. Hope that you do not need a new DAS module.

I do not have a schematic but that seems odd. I would think the sensor would be grounded all the time but that is just a guess. Maybe Arthur knows.

The key remote is busted . .. seriously neglected vehicle, how sad. No lights on mirror when starting. There is fuel being pumped . . . can hear the pump, and checked fuel pressure and all good. I did consider the DAS module, but don't have the equipment to test it (plus busted remote). I am thinking of sending it to Dealer and let them figure it out. Did notice the fuel pressure regulator leaking, but don't believe that will cause the injectors to stop functioning.

And yes, have large ring around ignition switch.

And there was no voltage when cranking the engine at the cam sensor. It all points to the ECU not grounding circuits it should be grounding to start and run.

If you unplug the cam sensor and turn the engine over, you should have voltage from the sensor..that is the point I was making..if no V from cam sensor, then the sensor is bad, the reluctor gear is bad , or the gap between the two is too large.
The gap is spec .4-.5 mm..and the V spec. is .8-1.5 at crank.
It is an ac signal and it gets converted at the ECU...so I would still look there...