GPrime2

I've tried as much diagnostic work as I can before posting in hopes that someone knows more than I do about these cars. I have a 2007 S600 that has been an absolute joy to drive until recently it started having intermittent starting issues. I believe there is an issue with the throttle body, as the throttle angle reads 8.6 degrees with my foot off the throttle (acceptable range per my scanner is 0-2.4 I believe). My main question is can the electronic throttle body issue cause a no start condition on this car?

I've eliminated spark from the equation by spraying starter fluid directly in the TB and it starts. I removed the fuel pump and bench tested it, it runs correctly. The fuel pressure reading from the scanner is in the 40psi range, raising to the mid 50s during starting. There is fuel at the rail, I have not tested the actual pressure at the rail, I've only depressed the schrader valve to verify fuel spraying out, the pressure seems consistent with the pressure readings. I've tested injector pulse at the injector connectors, they seem to be working correctly. I've also changed the crank position sensor just as preventative maintenance and to rule it out as a possible culprit. Any ideas?

I have a Maxidas DS708 available to scan any system, so if anyone needs a specific reading to help with diagnostics, I'd be happy to rescan the car. A few other things I've checked, cam position hall sensor is reading correctly, crank speed is reading correctly, batteries are both fully charged and crank is strong.

Plutoe

post the VIN!!

GPrime2

WDDNG76X97A100249

Plutoe

Although you may have an issue with the throttle body, that inappropriate position for starting would not stop the engine on.

However if you have an issue with the drive auth system that would let the starter to continue to crank but the ECU will not authorize engine on.

If you have a second key---give it a try---what happens!--if the same then its back to diagnosing all the starting sensors--cam, crank, temp bla bla

Also you haven't screwed width\or changed any of the engine start control modules!!

GPrime2

It's not the drive auth system, immobilizer is good to go, key is recognized and it's giving green lights across the board for drive auth in the scanner. Cam crank and temp all seem to be giving correct readings to the scanner. I'm going to test the fuel pressure at the rail this afternoon, do you happen to know where the fuel pressure is read in these cars? I seem to remember the fuel pressure sensor is on the filter/pressure regulator in the tank, which could mean it's losing pressure somewhere downstream from the pressure sensor.

If I'm not mistaken, drive auth would shut down spark as well, the car has good spark and sputters with starter fluid. If it's not the throttle body causing the problem, it's gotta be in the fuel system somewhere.

GPrime2

Checked pressure at the rail, ~45 after being primed, ~53 during starting. I checked the injector pulse again, it looks like the voltage is low, only spiking to about 1.5-2v. Back to the diagnostic grind.

Plutoe

Post the VIN!!

GPrime2

Already posted it. I did a bit more testing with the scanner today and everything keeps pointing back to the throttle body. I did an active test at idle and the throttle angle was sitting at 8.6 degrees when the test wanted 0-2.4 for idle, I also did an active test for full throttle where the test wanted 75 degrees or more on the throttle angle and foot to the floor the best I could get it to read was 38.

It turns out the M275 engine doesn't have a mass air flow sensor, which I was going to be suspecting next, and uses a combination of the throttle body, map sensor, and upstream/downstream pressure sensors to calculate engine load. I mention this because the scanner is reading a calculated load of 87.5% with it not even running. I went ahead and ordered a throttle body for it, even if that doesn't make it start it looks like that was an issue regardless. Will post back when it arrives. I'd be happy to entertain any other ideas of what it might be in the mean time.

Edit: tested the map sensor, it's reading 980 hPa with the engine off and drops slightly while cranking. 980hPa is damn close to atmospheric pressure, so it looks like the map sensor is doing its job correctly.

Polar Bear

Just wondering - what is the mileage on the vehicle? I have never heard of one doing things like that or having a TB issue. Any other issues in the past?

GPrime2

It's got about 75,000 miles on it. I've only read of a few TBs going bad on these, but unfortunately it's not a super common motor so even the common issues aren't happening to people THAT often. Combine that with the fact that most people aren't going weekend warrior on their V12 mercedes and you end up with a pretty short list of common issues.

I'm just following what the scanner is telling me, I'd definitely be more confident if it were saying it was something else, but literally every other sensor is reading correctly and everything I've suspected is doing its job.

bmwcrocop

I had the same issue with $500 worth of diagnostic time to figure it out.

Try to Switch out the fuel pump modules in the fuse box.

GPrime2

I was going to go looking for fuses next, but it seems like everything is getting power, unless there's some weird voodoo with the fuel pump module, the pump is getting full power when it's supposed to and there is full pressure at the rail (verified with a tester in addition to the scanner). In your case, was the fuel pump getting power when you had a bad fuel pump relay? (I assume you mean relay not module, unless there's a module in the fuse box that I don't know about).

bmwcrocop

Yes pump had full power.

Here was my post: months ago the car wouldn't start (in one out of four tries). The starting got progressively worse. I replaced the crank shaft sensor to no avail. The mechanic tested the fuel pump and it was good to go. He replaced the Fuel Pump Relay (A 002 542 13 19) and it worked perfectly.

Good luck

GPrime2

That would make more sense to me than the throttle body would, especially if that relay controls the injectors. I assume it's in the rear SAM, any idea which one it is? I seem to remember there being 3 or 4 relays of the same size back there.

Edit, nevermind found them, looks like there are 2 relays and a module for the fuel system, do you remember if the one you replaced was in the front or rear SAM? It looks like the rear one is formally called the fuel pump module relay, so I'm guessing that one.

alx

Checked your fuel filter? Dirty filter will reach appropriate fuel rail pressure but once you crank it might provide sufficient flow for starting.

GPrime2

I think that'd be a bit of a stretch, especially since I'm not getting even an attempt to start from it, spraying a little starter fluid gets it to sputter and I'm thinking if you were right it'd sputter but not start. The TB should be here tomorrow, and I'll try swapping the fuel pump relay with the cigar lighter relay just above it to see if that does it. Will report back tomorrow.

alx

Err. I meant once it cranks it might -not- provide sufficient pressure to start.

Let us know how it goes.

Have you reset throttle body adaptations/ teached in new body via das? However I do not believe it is a throttle body issue but more fuel rail pressure one. So pump, relays, ecu... In that order.

bmwcrocop

Yea the rear SAM. do you have a picture of the rear Sam? I can look as to which one I replaced

GPrime2

I found it, it was Relay S in the rear sam, I accessed it through the panel under the rear armrest passthrough thing, and from that view it was lower right, I swapped it for the cigar lighter right above it (same relay) and no difference in starting. There's another fuel pump relay in the front I'm going to try a bit later today, and hopefully the throttle body will be here today as well.

GPrime2

It's definitely not a fuel rail pressure issue, it has correct pressure and I tested the flow of fuel and it's good. The pump is running correctly, the injectors are not pulsing enough voltage to open. I doubt the throttle body will fix it as well, and yes I tried resetting the throttle body adaptations. I just swapped the relay with the cigar lighter relay right above it, no change. If the throttle body doesn't have any effect, I'm stuck with swapping the ME/ECU I guess. I'd probably take it to a stealership to make sure that's the issue first, since the ME is giving no indication of not working correctly, every sensor I've asked for a value from it has come back with a value without any issue.

GPrime2

Progress! @Bmwcrocop you're right, the fuel pump relay is not necessary for the pump to run, i removed it completely and tried starting the car and still got plenty of fuel flow. At no point do I hear it clicking though, even after switching it with the cigar lighter relay. So there appears to be an electrical issue back there, time to trace it.

alx

if you have enough fuel pressure at crank time and good flow, but the injectors are not pulsing at all or not enough- i would say it is an ecu problem...

GPrime2

Ok now we're getting somewhere. There is no voltage at pin 30 on the relay base. It should read 12V constant (I even checked with the key in the on position to make sure it doesn't have power only when the car is on), so there's a fuse or wiring issue somewhere upstream from the fuel pump relay. I'll check my wiring diagrams tonight and start tracing where that relay gets its 12V constant from, and start backtracking from there. I checked the fuses, they checked out.

Mo_Qazi

Why dont you take the car to the authorized dealer and get a diagnosis? I believe the will do diagnosis free of charge..

bmwcrocop

Because this issue does not show up on the star computer.