05 e320cdi-- random no crank/no starts- no codes
 

This recently started

Turn key- get normal lites/GP lites/ etc. Go to crank-- NOTHING - as if battery is dead...

Battery is 12.5 v

Happens several times over 15 minutes--

then randomly starts
also-- weird- same as above-- zero crank-- then as i am returning keyfob to OFF-- halfway on return-- it cranks and starts

also- has happened - were all of the above-- cranks/starts on return-- then when i return key to OFF position-- car stays running???

ANY IDEAS????

When you say no codes....did you scan with a scanner that reads all MB codes?

I've had some issues with the first part of your description - the no-start situation.

Next time you start the car keep an eye on the glowplug light immediately after you switch the ignition into position #2.

The glow plug cycle on the CDI's is very, very short but you should always see the light come on for at least quarter second before going out.

If you don't see the glow plug light and the car won't crank/start I've done some diagnosis that might be helpful.

I haven't experienced any of the other symptoms you've described so my info may not be relevant.

Tim- I actually experienced the No Glow plug lite/No crank last winter... Fixed with ECU rebuild and re-program.

This time-- the Glow plug lites do come on every time,,, then no Crank or as explained --random cranks/starts

My Indy does NOT have Star-- but is a legit Mech w/ Some pretty good expensive toys

You need to check the electrical part of the ignition switch as it should not stay running with key in the off position and also should not try to crank when you are in process of turning it off.
Not sure how it’s all held together on the ignition barrel but it sounds like it’s got loose and is moving around.
You are not going to have any codes because technically nothing is wrong as such.. if it is a loose electrical portion of switch then it’s moving as you turn the key so it does not reach the crank stage as the whole unit may have turned rather than the insides clicking round.

Got it. Where did you get the ECU? They appear to be totally unavailable even from Mercedes?

I have the Starfinder and wiring diagrams at my shop - do you have access to them? Haven't researched it but I think the starter motor signal comes through the front SAM and utilizes a cube relay to provide the actual starter solenoid signal. I believe the ECU initiates the signal but I'm not sure.

Could be as simple as a flaky relay. Or it could be much more complicated.

Let me know if you want me to dive into the schematic for the starter circuit.

TIm

This car is about 8-10 years too new to have a ignition switch that is actually a switch or has any tumblers in the key mechanism.

Thanks- I will let u know

More info now--

apparently the indy- has found when it goes into NO CRANK-- the tach is bouncing from 500-900 rpm NO CRANK/NO Motor running...

when it DOES start (Randomly) the Tach is at Zero- like it should be when in Glow plug lite position... in other words when he initiates GP Position and sees NO TACH move - he knows it will be a successful crank/start

when he turns to GP Position and sees Tach Movement-- he knows- it will be an NO/CRANK/NO START

hope that helps some guru's out there

Well that's not good - that symptom wouldn't present if it was just a stuck starter relay.

The tach signal would almost certainly be coming from the CDI control unit and it appears to be confused.

Are there any codes in the N3/9 CDI ecu?

As a pure guess could a bad crank position sensor be feeding a spurious signal into the process that's making the ECU think the engine is actually running when it's not? That would explain the no-start when the tach is moving around prior to starting.

I generally don't agree with the crowd around here that proclaims The-240D0-OM61X-is-the-best-thing-ever-made crowd but in this situation they are absolutely right. Even with a SDS it's very difficult to diagnose this kind of intermittent problem and once you get into the mysteries of the black box ECU there are really no possibiliites of fixiing anything once you verify the inputs are correct.

As mentioned before it sounds like a wonky ignition switch to me.......or like was possibly a bad crank position sensor, but that would most likely throw a code.... If possible, try another ignition switch??

It is only a guess. It never happens to my CDI, touching wood.

I suspect it is something electrical loading the battery if the tach is bouncing around. May be a bad starter or weak battery. Try something simple first. Turn on the headlights and see whether it dims badly when starting. Try a new battery. Good luck.

Ignition switch module not certain if a foxwell can test it but I would think so.

Indy checked Both the Crank position sensor and camshaft sensors- both appeared ok...

I heard about a diesel GL that would start/run for awhile then stop running. It was very sporadic. Guy sold it to new owner for $2k. He found a flooded rear SAM module. Replaced SAM and never looked back on hit new $2k ride:).