zer0pwn

I have a 2003 ML350 that has been having intermittent issues with turning over. When I turn the key it cranks consistently but just doesn't seem to catch. This is usually after driving in the summer heat and leaving it parked for a little while. I will try to go somewhere else and the car will just not turn over but 15-30 minutes later it will turn over. I have been thinking it is a battery issue so I have been jumping it but the battery is known to be good and so is the alternator. I read somewhere else on the internet that it could having something to do with the crankshaft position sensor or just a faulty fuel pump. What is weird is that it only happens in the heat. Somewhere else someone was talking about their coolant leaking onto their crankshaft position sensor and shorting it and it seems similar to my situation because my coolant was low a couple weeks ago. I haven't seen any coolant leaking or any leaks under the car. I had it taken to a shop but they couldn't find anything. I am thinking of taking it to the Mercedes dealership but first I am going to have the codes read and see if I can fix it myself... Full disclosure I do not know much about cars but I am wanting to learn! If anyone has any ideas I would love to hear them... This is so frustrating because I rely on this car.

Thank you for your time,
Will

khomer2

Welcome Will.





1) How do you know the battery is good? What's the magic V you read at the battery terminals? Anything less that 12.3V is dead, imo.
btw, if you have been jumping the battery, what does that tell you?

2) FP - Check the FP at the rail - Lots of DIY info "how to" here on the forum you can read up on, or google it.

3) It could very well be your CPS that needs to be replaced.

4) You took it an indie and they came up with nothing? Not even a scan for codes? What about the battery V check? or the FP check? What exactly did they do?

zer0pwn

Hi Khomer,

1) With my Dewalt battery jumper I am reading about 12.6-12.7V, I will have it checked again tomorrow at Oreilly's along with the alternator. I have been jumping the battery, but I have a feeling it isn't doing anything because today I was jumping it and it wouldn't work. The indie shop and Oreillys confirmed a good battery and alternator.
2) I will get this done tomorrow it is currently 12:20AM here
3) Yes I am not sure, I have a Check Engine light that is consistently on so here is to hoping for a code logged in the computer *fingers crossed*
4) I am convinced that they didn't do #$!&... It may have been my fault because I didn't know what to ask for. I came in complaining that it was having intermittent starting issues and that I thought it was the battery. He checked over the vehicle for shorts I believe and found low coolant and a couple aftermarket circuits (backup camera and stereo system). There was a blown fuse coming off the positive battery post. I don't think he even replaced the fuse. 150$ for coolant.... I guess when you want something done right you do it yourself. I am thankful for the knowledge of this forum... It seems too often that indie shops like to take advantage of young people.

Thanks for your time,
Will

khomer2

You can, from one of those shops like O'reilley's, borrow a scanner to read any saved codes. if you dont own one yet.
Keep us posted on your progress

zer0pwn

So I went to NAPA and O'reilly's today and got a OBD code reader and a fuel pressure gauge and here is what I found.

1) Fuel pressure looks good, about 50 PSI before cranking in Key Position 2 and 56 PSI consistently even when revving to 2000 RPM and 4000 RPM.
2) OBD Reader pulled 3 codes. First code was P0410 which is relating to a relay my dad removed from the secondary fan system... He was seeing it running 30 minutes after shutting off the car and it worried him so he removed it. I think I am going to replace this relay because it seems like a moderately severe issue.
Second code seems to be the ticket: P0335 (Crankshaft position 'A' sensor malfunction). Seems like my initial suspicion of the CPS being the issue was right.....
Last code was P0123. I have been having issues with the car going into limp mode after hitting the kickdown switch so this code makes sense. I can't believe how useful these codes are (especially for a 60$ reader!).

Guess I am getting a new CPS sensor to fix this intermittent starting issue? I am looking at Bosch 0261210170 CPS...

Thanks,
Will

khomer2

You should see if the reader can also scan the other modules. If you plan on DIY, then you want one that can scan all the modules, imo.
It's a good investment.

As long as the CPS is oem, no generic no name stuff and from a reputable seller.

Keep us posted on your progress.

zer0pwn

So I ended up replacing the CPS sensor (after some difficulty...) and got it up and running. Haven't had the problem since then, but its only been a few days. Will keep you guys posted on the status of it.
New codes popped up however.... P0171: System Too Lean (Bank 1) and P0174: System Too Lean (Bank 2)
Not sure if it's related. Will look into this separately. Still have a code with the accelerator sensor too after soft resetting it.

khomer2

Mileage on the suv?
Either a vacuum issue or the MAF.
Has the MAF ever been replaced? if so, generic or oem?

zer0pwn

About 181,000, MAF hasn't been replaced AFAIK.
Should I clean the MAF first and check for leaks?

khomer2

Yes to both.
CRC MAF cleaner or equivalent.
Check all lines for cracks, breakage. A DIY smoke machine is good for these older vehicles and brittle lines.

Put the pedal to the metal and see how it does too.

zer0pwn

I used CRC MAF cleaner and so far the codes haven't popped back up. Gonna try building the smoke machine too to check my lines.

khomer2

Keep us posted on your continued testing.
btw, if your scanner is capable to read live feeds, look at the STFT LTFTs and post.

zer0pwn

Codes popped again, I am pretty sure it's unmetered air because both codes are consistently popping. I am gonna check the vacuum lines.

chassis

This is a great thread and a good example in my view of how owners can help each other own and operate these vehicles.

Kudos to @khomer2 for the advice.

Maj. Dundee

When you replaced the CKP, you probably cracked one of the vacuum hoses at the same location of the CKP.

zer0pwn

I think you are right. I found this near the top right of the engine bay. Not sure what this part is that I cracked. Can you tell me what I need to replace? Pictures below.


Maj. Dundee

Those photos are very narrow and I cannot make heads or tails out of them.

Post a photo of what is exactly broken.

khomer2

Dont forget to build your SM.
It's a simple and invaluable tool for these old suvs.

zer0pwn

I make a smoke tester and found the leak. It was on the air intake hose right after the MAF sensor.


khomer2

Couldn't see clearly if the leak was thru a crack on the hose or at the seal.
Either way you may be able to patch that, or head over to the PnP to find a replacement, or order a new one ($$$)
Glad you found it.

zer0pwn

It was at the seal, it’s not a crack but looks like it just isn’t on all the way. I tried to push it on all the way but couldn’t get it so I ordered a replacement. I will see if that clears the codes.

zer0pwn

So that part has been replaced, but it still hasn't cleared the codes. I noticed after a second look that the MAF sensor is a Bosch and not OEM... Do Bosch MAF sensors send codes when the sensor is bad? I can test it with a multimeter, I saw a procedure on YouTube. Any suggestions from here? I will smoke it again tomorrow to check for further leaks.

khomer2

Which codes popped up again please.
Bosch is oem, but you have to make sure its from a reputable seller. The ones on (fleabay,as an example) that say they are "genuine bosch" for inexpensive - They are also untested chinese crap in a Bosch box.(My take on these)
Just order a MAF sensor unit, not the whole assembly, if it's still good.
MAF sensor test

Post #11

MAF ALERT

Just remember, The maf sensor does more than just measure airflow. It also incorporates the Intake Air Temp sensor.

zer0pwn

I found a loose hose and pushed it in and now I haven't had the codes come up anymore. I heard a leak when looking under the hood for something else and just started pushing hoses and it made the hissing noise go away. Now all the codes are not popping back up.
I have power steering issues now though so I am going to make a new thread.

khomer2

Your smoke (re)test did not find this?