Intermittent No-Start Issue on Bluetec
09-11-2017, 10:31 PM
#1
Member
Thread Starter
Intermittent No-Start Issue on Bluetec
2012 GL350. It started as an occasional thing, but it's getting a little less "intermittent" and a little more "just leave the car running". When I go out in the morning or after work, it starts up just fine. Sometimes it cranks for a little longer than usual, but no big deal. If I back it up to the trailer, shut it off, hook up the trailer, and then try to restart, it might start right up but it might crank without starting two, three, four, fifteen times before finally coming back to life. If I shut it off and turn it right back on - say within about 30 seconds or so - it starts right up. Or at least, it has started right back up every time I've tried that experiment. It is an intermittent problem of course.
I have codes for the servo motor not working (I'm not in limp mode because I've got the resistor in place) and sometimes when this happens I have a code for something "shorted to positive". Once it was an O2 sensor, and once it was a cooling fan, I think. Honestly, I'm not 100% sure what it means to short to positive. I've shorted things to ground a million times and have the scar tissue to prove it, but I can't quite wrap my head around this one.
For a while, if I would turn the steering wheel while it was cranking it would fire up. Then it stopped doing it for a while, and now we're back to it -- but this time that trick doesn't work. It may have just been co-incidence before, of course. I can't recall off the top of my head what may have changed when the problem went away for a while -- it's possible I may have used fuel from a different source for a period and then went back, but that doesn't seem too likely to me. Battery was tested by the local tire shop today as part of their regular service when they put four new tires on for me and it came back "good", but I'm not sure how much I trust their test. I do know that it doesn't sound sluggish when it turns over, but I have absolutely no idea how old the battery is.
Any ideas on where I should be looking? What I might try to test the next time it happens? My thought was to maybe try to pull a fuel line from the filter to see if I'm getting diesel from the tank. Could the pump somehow be heat soaking after running for a while and then sitting without any coolant (fuel) going through it? I'm at a bit of a loss and it's kind of a point of pride to not have to take it to the local dealer =)
I have codes for the servo motor not working (I'm not in limp mode because I've got the resistor in place) and sometimes when this happens I have a code for something "shorted to positive". Once it was an O2 sensor, and once it was a cooling fan, I think. Honestly, I'm not 100% sure what it means to short to positive. I've shorted things to ground a million times and have the scar tissue to prove it, but I can't quite wrap my head around this one.
For a while, if I would turn the steering wheel while it was cranking it would fire up. Then it stopped doing it for a while, and now we're back to it -- but this time that trick doesn't work. It may have just been co-incidence before, of course. I can't recall off the top of my head what may have changed when the problem went away for a while -- it's possible I may have used fuel from a different source for a period and then went back, but that doesn't seem too likely to me. Battery was tested by the local tire shop today as part of their regular service when they put four new tires on for me and it came back "good", but I'm not sure how much I trust their test. I do know that it doesn't sound sluggish when it turns over, but I have absolutely no idea how old the battery is.
Any ideas on where I should be looking? What I might try to test the next time it happens? My thought was to maybe try to pull a fuel line from the filter to see if I'm getting diesel from the tank. Could the pump somehow be heat soaking after running for a while and then sitting without any coolant (fuel) going through it? I'm at a bit of a loss and it's kind of a point of pride to not have to take it to the local dealer =)
Last edited by wae; 09-11-2017 at 10:35 PM.
09-19-2017, 10:21 AM
#2
Member
Thread Starter
I've continued to try to troubleshoot this and found a few more data points. I realize that correlation does not causation equal, but with enough data, patterns may begin to develop.
- So far, it hasn't happened when the tank is 1/2 or more full.
- 15 minutes of shutdown doesn't cause the problem, but 45 minutes will.
- OBD2 live data shows an RPM count when it won't start, so I assume that means that the CKP is reading correctly.
- OBD2 live data also shows between 1000-2000 PSI on the fuel rail when it won't start and when it does start, so I assume that means it is getting fuel.
- So far, I've tried turning the key to the run position and waiting for about 5-10 seconds before flipping all the way to start. It hasn't failed to start with that method yet.
- I think my last tank was Kroger fuel, this tank is UDF fuel. I have no idea if there's any difference or if the diesel even comes from different places, but we shall see.
- I can hear a hum that sounds like a fuel pump every time I turn the key to the run position whether it starts or not. But then, there are a million whizbang devices in this overly complicated gelaendewagen, so I'm only guessing that it's a fuel pump I hear. What is odd is that every other fuel pump I've listened to does a priming pump on key-on and then shuts off until it sees RPMs. This is a constant hum that just stays on. But perhaps I'm just more used to returnless systems? I don't know.
I'm really baffled by this -- I can't think of anything that would cause this issue only when it heat soaks for a while but never when it's cold and never while it's just running down the road.
- So far, it hasn't happened when the tank is 1/2 or more full.
- 15 minutes of shutdown doesn't cause the problem, but 45 minutes will.
- OBD2 live data shows an RPM count when it won't start, so I assume that means that the CKP is reading correctly.
- OBD2 live data also shows between 1000-2000 PSI on the fuel rail when it won't start and when it does start, so I assume that means it is getting fuel.
- So far, I've tried turning the key to the run position and waiting for about 5-10 seconds before flipping all the way to start. It hasn't failed to start with that method yet.
- I think my last tank was Kroger fuel, this tank is UDF fuel. I have no idea if there's any difference or if the diesel even comes from different places, but we shall see.
- I can hear a hum that sounds like a fuel pump every time I turn the key to the run position whether it starts or not. But then, there are a million whizbang devices in this overly complicated gelaendewagen, so I'm only guessing that it's a fuel pump I hear. What is odd is that every other fuel pump I've listened to does a priming pump on key-on and then shuts off until it sees RPMs. This is a constant hum that just stays on. But perhaps I'm just more used to returnless systems? I don't know.
I'm really baffled by this -- I can't think of anything that would cause this issue only when it heat soaks for a while but never when it's cold and never while it's just running down the road.
10-29-2022, 06:33 PM
#4
If Xentry can do a better job with diagnostic then it might be worth taking the car to a dealership.
The MB workshop will tell you how much to fix the problem and what's involved so just take the report home and DIY.
The MB workshop will tell you how much to fix the problem and what's involved so just take the report home and DIY.
