dubsnow

picked up the car for a good price from a repo lot here on base. ran codes before buying it and all that popped up was "camshaft position sensor". got the car somewhere and replaced it with an OEM mercedes part. was turning over and starting at first but only briefly and then stumbling and shutting off. fuel seems to be flowing fine but then the battery died. apparently its a special battery so i replaced that this afternoon but now it just turns over and doesnt start at all. funny thing is its still throwing the code for the camshaft position sensor even though its less than a day old. would really love to solve this without dropping a ton of cash (euro) at a shop. im based in germany so the exchange rate kinda rapes us. does anyone have any ideas on something else i could check? or is there a special procedure to get the sensor to work properly? or could it even be something else?

on another note a buddy is a diesel mech and he pulled a fuel line and its got good pressure. on a small scan tool it read 190 psi for the fuel. not much into diesels so im not sure if this is good or bad. oil is good also. any ideas? and i swear if someone can help me im willing to paypal money as long as it starts up and drives off the lot its sitting at


Have swapped the camshaft position sensor yet again with no positive results. I did however find out there is no fuel past the pump/filter. Unscrewed a fitting from the fuel rail and tried cranking it....no fuel at all on either side. So now I know its.not getting fuel. Any thoughts?

Micah / AF1 Rac

Fuel rail pressure should be in the 1600 Bar range, or like 23,000 psi if similar to my 06' CDI. There are also two batteries, one small auxiliary battery under the hood, I replaced mine with a Yuasa YTX14BS from a motorcycle shop (stock on some Aprilia and Moto Guzzi models) and another much larger and more expensive battery in the trunk area. Replacing batteries on these cars requires a little specialized procedure than on say my 92' Honda. Read up on that, plenty of info out there.

If fuel rail pressure really is only 190 psi the car will not run. If MAF or Mass Airflow Sensor is disconnected or bad similar bad things can happen, I have the same motor as you in my Sprinter truck and it ate a MAF sensor recently resulting in horrible running in a sort of limp home mode.

dubsnow

The 07 (according to the dealer) doesn't require a special procedure after replacing the battery. I did replace it with an OEM unit (245€) and it's cranking alot better...but still not starting. And the 190 psi is from a semi good reader that can do live data. Now if I could get it running even in limp mode I'd be thrilled. But even with all the issues the only code it wants to throw is camshaft position sensor.

Micah / AF1 Rac

Well, I hate to say this but...after dealing with a similar issue with a Miata recently...you might need to inspect the cam itself. On the Miata I was trying help the owner with the tab that the CPS reads on the camshaft had sheered off...no number of sensors could pick up a signal off a missing tab. I seriously doubt that is your issue but figured it might be worth mentioning. Can you scope the signal generated by the CPS? That might tell you a lot.

pellar06

I would address the fuel issue. you should have fuel coming out of the fuel filter when key is in position two. It has a electric pump that feeds the HPFP. Open the black bleeder screw on the fuel filter and wait for fuel to come out with the key on. Then try to start it. As a last resort you can crack open the crossover fuel lines on the rail when cranking. Do not open them much because of the high pressure just like a quarter turn and once you have fuel running out shut them. As stated before extremely high pressure is needed for the car to run. If this does not get it running then there might be a mechanical issue that is related to the camshaft sensor.

SmokinReefer

Has happened to me twice on two different ML350s. Dealer decided it was one of the two fuel pumps after trying the CPS both times. The pump replacement corrected the problem.

I think when the pump in the fuel tank goes, the computer knows it and the car won't even turn over.

dubsnow

I'll give this a shot tomorrow. Like I said though we had fuel coming out of the lines when we popped them off but nothing was in the rail. And are both pumps in the tank? How easy are they to access? And most important...what do they run lol...

dubsnow

Duplicate post and couldn't find the delete from my phone.

Micah / AF1 Rac

Boost pump, or electric portion of the fuel pump system is located in tank (I think, most cars are) but the Bosch high pressure mechanical pump is engine driven and located either on a cam drive or drive output shaft on front side of motor. On my inline six version it is at the front of the motor very near to the camshafts drive area. Follow fuel out line from filter assy to next thing it feeds into, this should be the mechanical, high pressure, fuel pump. It's not cheap, not at all.

dubsnow

Anything special to swapping it out though? If that IS the issue? I'm pretty sure I know the part just need to know is it a swap job or is it different with a diesel...

Micah / AF1 Rac

Not a hard job really, just an expensive part. If the car was ever run dry of fuel then the high pressure pump can fail VERY quickly, I don't even let mine get much below a quarter tank I'm that scared of damaging the pump diesel is a killer lubricant, air bubbles, not so much.

pellar06

The High pressure fuel pump is the black thing on the driver side front of the engine. you should be able to follow the lines going in and out. The fuel lines going in are the rubber ones coming from the filter. The output lines are the metal lines that go to the rail. It should be pretty much plug and play.

dubsnow

Just figured it out...not a fuel issue. The timing chain broke on the passenger side. Looks like the gear sheared. So gonna break down the head and make sure no valves were bent. Anything else I should check? I know I'll need head gasket set, bolts, chain, gear...anything else? First time I've torn down a head but I'll have help. Anythings I should look for? Any way to test other items without actually pulling the motor?

Micah / AF1 Rac

Well that does nicely explain both the lack of a CPS signal and the lack of fuel pressure, make sure you look long and hard for every little broken bit, I had a scooter motor come in today, failed cam chain, which led to failed valves after piston hit them, to failed piston after it cracked in half...literally chasing down hundreds of little bits of metal in the remains of the motor cases for a rebuild. Buy nothing yet, tear down and inspect, if damage goes much further than a cylinder head look for a replacement motor that runs, always cheaper and easier to get going in a situation like this IF there is extensive damage. Sorry to hear that.

dubsnow

Pistons look great on the upside....but all the rocker arms were broken so I'm assuming the valves took the brunt of the force. Not that bad since they are 36€ each from mercedes. For parts minus a cam which has a light scratch in it it's about 1300$ US. Thinking about seeing if the cam can be machined. If so then I'm out alot less than expected. Hopefully the other head is.fine. still trying to figure out how it happened though. Motor still cranked so it's not.seized. any ideas?

Micah / AF1 Rac

I would personally replace ALL valves in the effected head, have a good cylinder head guy to the install and inspect the seats for damage, the valve guides would also get replaced as well as the stem seals and camshaft and actuating arms. Got any pics?

Isentropic

Do you think my fuel pump has gone bad too? Our 08 Bluetec vehicle cranks, but won't start (it's below -10 deg. F where the car is). I have already tried jumpstarting, with no avail.

Also replaced all glow plugs and glow plug module.

How can I check for fuel pressure, or if the fuel pump is working?

Thanks much.