Hello
A common cause of this problem is a defective fuel pump check valve, hook up a fuel pressure gauge to the fuel rail test port and verify there are no leaks, start the engine and let it run until the fuel pressure is steady, then shut it off the fuel pressure should remain within 5 PSI of the running reading, if not then the fuel pumps built in check valve is defective. The reason this causes hard starting is the fuel drains out of the line due to the defective check valve, when you start you get air to the injectors for a second, this causes rough running and a stall in some cases, 2nd restart in most cases is ok. Do the leak down test and let me know the test results.
PS: Your cars design of fuel pump is prone to this type of leak down problem. The fuel pump is located inside the fuel tank, in most cases the fuel pump is accessed by dropping the fuel tank out of the car.
My experience is 30 as an electronic engine control technican (we are called EEC techs), I also have a Master technician certification in all phases of repair.
I did the fuel pressure check. The running pressure was 42 psi which is less than the specified pressure of 55-59 psi. When I shut the engine off the pressure was 0 psi.
Hello again
You definitely have a defective fuel pump, the pressure should stay within 5 PSI of the running pressure after the engine is shut down for at least 24 hours, also the running pressure is well below the factory specification, so if you change out the in-tank fuel pump I am sure you will cure the problems you have. I have provided accurate help and appears I have helped you to isolate the problem, so could you please rate my help for FixYa.com com as "HELPFUL", It is how I'm compensated for my time. Thank You.
emissionwiz
Unfortunately the new fuel pump did not solve the problem. I did the fuel pressure test with the new pump and I still lose pressure when I shut the ingition off. I did notice when I turned the ignition on the gauge would pressure up and then go to 0 even with the ignition on.
Then you have leak.
Check the whole system, isolate the fuel injectors and the fuel pressure regulator, the diaphragm may be leaking into the engine vacuum hose.
Fuel pressure regulator is integral with the fuel filter and it was replaced. If I have a leak, I would think I would see fuel somewhere?
I have the whole fuel system exposed. There is a new fuel pump and a new fuel filter/pressure regulator. The fuel pressure regulator is working fine when the engine runs. I don't see any fuel leaking or hear any pressure loss. The fuel filter/pressure regulator has a line from the pump and a return line on one side. On the other side there is a line to the fuel rail and another line to the vent. When I turn on the ignition, the pump kicks on the fuel rail pressures up and the pump kicks off causing the pressure to drop at the gage. There is nothing else between the fuel rail and the filter/pressure regulator. Everything seems normal to me.
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Have a 2004 mercedes c230 with 145k problem accelerating wont go past 25miles even if floor peddle at time a rpm rev as if stuck in fist gear what can problem be
Yes that correct their is a sensor on the cylinder head for the autochoke which isnt working also on a car like this they often come with a ambient temperature sensor as well which reads the air temp and the two readings are computed to give the right amout of fuel without overchoking the vehilce ,its these californain regulations that require all this stuff which is now on the europeon vehicles as well as its cheaper to make just one wiring loom and i know you will not like this answer but as this is a recent vehicle unlike the older ones i get in for repair i would advise you to bite the bullet and take the vehicle to a merc garage that has the software to sort the problem out,Now i now that american software on this vehicle is more user friendly that that on our europeon models at least you can read codes.But sometimes the faults require the correct mapping software and even a mechanic with 40yrs experiance like myself is bashing his head against the wall on a fault like this .
please remember this is a merc and the dealers pay a lot of money to have an agency which is why the software isnt easy so any person can read the code reader the software is down to the basic minimum to pass the emmisions test which unlike aor europen versions a sensor is placed in the exhaust pipe and engine run at 2500 rpm.to test a sensor isnt difficult you read the voltage at air temperate then drop in a saucepan of hot water (boiling) then check it again without burning your fingers ,I think you have a problem with the ambient sensor as this will detect the air temperature and set the fuel mix accordingly and without the correct dealer software you stand no chance of finding the fault .IF i knew where this ambient sensor was located i would tell you so you can change it but i have a feeling that if it is the sensor then the new one has to be calibrated against a set testing machine to make sure that its reading the correct temperature ,and knowing the mercs then this is a dealer only job as i cannot even change pads on the new ones and only the dealer can put the service light out on new 2011 models and if they dont do then car goes into limp mode after so long and the only way is to connect the vehicle via internet to the factory .Sorry i cannot help any further on this as i just do not know where this sensor is located ,it could be in the wing mirror iam thinking though but ?? Best i can come up with is take car to the dealer who has the correct software
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Why don't I get a check engine light for this auto choke sensor? Is there a voltage check that I can do to verify if the sensor is bad. I can read the ambient sensor under the bumper and see that it is reading correctly.
I am hearing there is an autochoke sensor that might be holding the choke closed or open. Wouldn't that only affect a cold or a hot start?
Another thought. If it is an autochoke sensor, I would expect the car to start fine either cold or hot? In my case it is difficult to start either hot or cold. Give me somethings to check and some way to check them.
Thanks for your help! It gives me some ideas and it does make sense. There is an inlet air temperature sensor near the throttle body and near the mass air flow sensor. I don't have a problem replacing it, but it sounds like it may have to be calibrated and simple replacement would not solve the problem. I would still like to ask around some before I bite the bullet and go to the dealer.
Thanks,
Tom
I have a 2004 Mercedes C230 Kompressor. It is starting difficult and sometimes sputtering after it starts. Once it does start it runs just fine. I have no check engine light. The fuel filter/fuel pressure regulator is new and the spark plugs are new. I can't find any vacuum leaks and I get fuel to the injector rail. Do you have any idea on what the issue might might.
I have been told it might be an inlet temperature sensor and that the sensor might have to be replaced/calibrated with dealer software.
Any other ideas or things I can check.
There are no codes in the ECM.
In addition to the above information there are no codes in the ECM. This is only a starting issue. Once the car starts it runs fine.
This still does no answer my question. The car has no codes diagnostic trouble codes.
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