AMGPirate

Hi guys, continuing to try and solve an intermittent starting issue I've been experience that has been getting worse as far as frequency of occurrence over the last few weeks.

At cold start in the morning or leaving work when the car has been sitting all day, the car will crank strongly and turn right over.

However, if I drive to work or anywhere else and get the car up to operating temperature, if I try to start the car within a few minutes of shutting it down it won't crank at all. If I leave it and come back after a few hours it starts right up.

Does this sounds like a temperature sensor failure or the starter relay?

It's so consistent with the temperature issue I know that's a major clue.

Does the w203 chassis share the same starter as us or does the C55 V8 require a more powerful one?

Thanks!

Morphh

Check with obd2 scanner, sounds like crank position sensor it's common problem for our cars

AMGPirate

Hey thanks for the quick reply. I should probably change the CPS since I have 140k miles on the car.

However, my understanding is with a failed CPS, the car will crank, it just won't start. With my hot start issue, it won't even crank...which made me think my issue wasn't as simple as a CPS.

Morphh

U have obd2 to check if there is any codes ?

C32izm

+1 def sounds like the CPS i've been through that not too long ago.

insame1

Please use the search function this has been discussed MANY times.

jhk777

This might help:

DTB
Date:
March 17, 2009
Order No.:
S-B-54.21/215a
Supersedes:
S-B-54.21/215 dated Feb. 11, 2009
Group:
54
Revision History
Revision
Date
Purpose
a
3/17/09
Technical Content Revised
-
2/11/09
Initial issue
SUBJECT:
All Models Equipped with Engine M272 and M273
Engine Cannot Be Started When Engine is Hot but Will Start After Engine has Cooled
If you receive customer reports in the above model vehicles that the engine cannot be started when the engine is hot but will start after the engine has cooled and there are no Diagnostic Trouble Codes stored in the ME control unit, check the signal that activates the fuel pump from the ME Control unit by monitoring pin 17 + and pin 4 on the small socket of N3/10 ME Control unit:
1. With the key in position 2 there should be 12 volts present across the pins, if not check the wiring from the ME control unit to the fuel pump relay or the fuel pump control module.
2. When cranking the engine, the 12 volts should go to 0 volts, if not it may be due to an open circuit in the ME control unit. In this case, replace the ME control unit and retest the signal to the fuel pump relay or the fuel pump control module. Refer to EPCnet for applicable part number. Note: A copy of the short test and all tests performed must accompany returned parts. If the documentation is missing or does not support the diagnosis, the warranty claim may be debited. Note: The following allowable labor operations should be used when submitting a warranty claim for this repair. This information has been generated on March 17, 2009. Please refer to Netstar 􀃆 Star TekInfo 􀃆 Star Time for the most current labor time allowance

WaveyKat

when its hot Pour some cold/Cool water down In the back with the CPS is if the car starts up its most Def your CPS..

jhk777

I thought it was CPS, also. Changed it on a Sunday (Autozone since dealer for parts wasn't open). Same problem. Finally took it to as Indy repair shop--they installed an OEM CPS--same problem. They discovered voltage problem to fuel pump when the ECU is warm and notified me of the TSB.

Kostas20

I had a similar issue, although my car would not start randomly, regardless of hot or cold.

Long story short, it turned out my ground connection on the fuel pump was melting and was causing the short on random occasions.

You should check for fuel pressure on the fuel rail when it doesn't start. If no pressure, lift up the back seat (it literally flips up easily) and check to see if you hear the whirl of the pump priming the fuel lines when turning key into position 2. Then I would pull the two connectors off the driver side - which houses the fuel level sending unit - and inspect your connections.

I went through changing the fuel pump before realizing it was a simple connection issue... hopefully you have a similar simple fix.

jhk777

Thanks. I wish it was that simple. I had checked all elec connections, which were fine. Replaced the rear SAM fuel pump relay and fuse. Then I replaced the fuel pump and the sending unit, because fuel pump output didn't seem that strong. I also suspected corrosion or poor electrical contact at the rear SAM, which was not the case. I had even tried the ice water on the CPS, which didn't help.
When the car starts it runs great. If there had been a short on an electrical connection to the fuel pump, I would have suspected intermittent loss of power on occasional bumps when driving.
179,000 miles on this 2007 C280--its been a very reliable car except for this recent starting problem.

Kostas20

I would honestly double check your wiring to the fuel pump starting at the pump and as far as you can get to the battery. I have read of many instances where our fuel pumps have led to melted wires, leads, connection points, etc. There is a thread somewhere where someones bottom back seat started to melt due to this issue.

I did everything you did before I noticed that one pin from the connector plugging into the fuel level sending unit was melted - the connector for the fuel pump. It would drive 100% completely fine but would randomly not start, and after a few attempts to turn over or leaving it for the night it would be 100% ok again.

jhk777

Appreciate your input, but I checked for continuity from the rear SAM to the (driver side) fuel sending unit electrical connector---no problem. The connector was in good condition, and the fuel pump and sending unit are both new.
As I said, the car runs great once it starts--I would really expect that any road bumps or potholes to cause enough vibration that there would be brief loss of electrical signal to the fuel pump to cause misfire if there were a poor wiring connection.

dinman

Another video


Now I'm sitting here with it running and it's at 11.6, pulling - 30-40 amps no matter idle or holding at rpm

dinman

So the amps were around -60 to -80 at one point of driving. 12v max. Dropping to 11.6. Then a few miles later, it shot up to 90amps, battery bumped up to 14.7v. Dropped back down to 30 amp, then maintained around 10-20. Then randomly,... Sinks to pulling from the battery even though the car is going 50 down the road. Voltage regulator maybe? Anyone know how hard to replace it on these cars? I have access to a lift this weekend and power tools

insame1

Dinman your in the wrong forum

dinman

I hate this phone. My bad, it always throws Me in the wrong thread

Morphh

Did someone put a underdrive pullies on it, u can get a voltage stabilizer to stop it from fluctuating, or it's the alternator regulator, or wiring to fuel pump

dinman

Delete, wrong thread

RLx02

Check your battery. I had the same issue with my car and everyone else said it was my CPS. I spend a morning replacing the CPS and still had the issue. Swapped in a new battery and it was golden.

thtguy

My C55 would do the same thing until one day it just quit. It was the starter. You are saying the car wont even turn over when it is warm. That tells me starter. Sometimes it would drag like it was the battery. But it was the starter. PITA to change. Have to remove exhaust and motor mounts (passenger side completely out driver side just unbolted). Go ahead and do motor mounts while you are in there. Oh and if you get a rebuilt from a cheapo auto parts store ( I don't recommend) because you are stuck away from home like I was. Have them bench test it. I had to do the install twice!

Daniel1223

Were you able to get this resolved?

I'm having the same exact problem

Khan 55

I would have expected the battery at first as well. It sounds like when you start the car when its cold, the battery would be drained to where it can provide enough power to crank. Now you drive for some time till engine hot, either battery over charging which I think it would unless it has a current draw somewhere maybe. And then when engine hot now car wont crank. Battery would be low on voltage at this point. Maybe after it cools down which is a significant amount of time, the battery stabilizes. So the alternator is the fault here as it isn't providing enough charge to the battery during engine run time. If that doesn't work then one should inspect the battery and the alternator using the various test methods available and from there see to what other causes of failure can attribute to this experience.

hkycoldrct

Anyone find resolution to the no start when the car is hot? I have the same issue after replacing the fuel sending unit and then the fuel pumps. Cold, it starts just fine. Warm, it will start but it's a hard start.

03MBC32

I had the same problem this month. Code scanner said it was the crank position sensor. Replaced the CPS and my problem was solved.