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Car Forum / Mercedes-Benz Cars / May 2006300E 89: Update
Jenns, Tom and others...I replaced the 02 sensor and the car did the same thing but idled for 15 minuts with the ovp connected. The check engine light appeared the while running time. I had to run over to my college campus; 2 miles way from my home with the OVP detached so it would not run rich. You guys have any other ideas? Will it hurt to run the car without the relay? I need the car to run. This is the worst time for this to happen....I had exams last week and I am graduating in two weeks...- chuck- monmouth county nj Hmm, if you can't troubleshoot by measuring the inputs/outputs the computer, you should get a diagnostic readout at an experienced garage. This should give some indication of what direction to look. You should be careful to run the car without the OVP relay, since you risk to destroy the catalytic converter. Too lean mixture will cause overheating and possible destruction of it, and too much unburned fuel will destroy it too. I would like to hear, what the problem was, when you have found it. The check engine light came on with everything hooked up (OVP, O2, etc.)? Run it over to Autozone and have then get the OBDI codes. Josh Yes with the O2 sensor and the OVP the Check Engine Light came on.....The car was in the driveway ideling for 10-15 minutes and then started to cut in and out and when i revved it up to 1000 RPMS it got steady for a minute and then bogged down...Waht else could be making it flod out with the relay hooked up?- chuck Earlier this evening I DCd the wire to the Cold Start Valve and the car idled for 20 minutes and was able to ride around the block with the OVP relay hooked up. Will disconnecting this wire totaly stop the flow of fuel out of the cold start valve? The check engine light was on during this wold time.- Chuck The cold start valve is controlled by the fuel pump relay to activate when the engine is cranked while cold ("Temp" signal comes from the ECU and "Start" signal from the ignition key as well as I remember). Do I understand correctly, that engine runs OK with cold start valve disconnected? If so, the cold start valve is probably OK, but apparently gets a wrong signal to open. That would definately flood the engine. If that is so, then fuel pump relay is probably bad. I did replace that about 1 year ago. But who knows, maybe it was a rebuilt one that went bad? Could it still be bad if the fuel pumps work?- chuck The cold start valve is a "break through" is solving this car's problems and I compliment you for thinking of disconnecting it as a test. Now let's think a bit about how this motor's cold start system is designed. In reverse order, there's the electric (cold start) valve; it seems to work as designed. Going backward, there must be a time / temperature relay (or something equivalent) that should be ON longer as the motor's temperature is lower and ON for a shorter time as the motor's temperature is higher. What powers the cold start circuit? Why does the motor run reasonably after warm-up ONLY: 1. if the cold start valve is disconnected or, 2. if the over voltage protection relay is disconnected? Someone who understands the cold start electrical circuit may have an answer to this question. Jens? There is supposed to be a temperature sensor for the fuel injection to take cue from... you need to ask the dealer which sensor that is... it is not related to the instrument cluster temperature sensor. However, to understand the whole thing... you really need a factory service manual to diagnose this problem. There is two coolant temperature sensors. One for the ignition control and one for the ECU. They are placed next to each other near the water pump. The ECU provides temperature output to fuel pump relay and instrument cluster. I think we are closing in. The fuel pump relay contains other functions then controlling the fuel pump. It also has relays for cold start valve and for disabling kick down solenoid. As I understand the circuitry, the cold start valve relay should both have crank and low temperature signal present to energize. So, once the engine is running, the crank is released, the cold start valve should deenergize and the ECU sholud take over mixture control. Apparently, the cold start valve relay is at least energized when the engine is warm, which it shold not, partly because the engine is no longer cold and definately because the engine is no longer cranked. I don't believe in a fault in both inputs, so I conclude on the fuel pump relay. There is no other ways, the cold start valve can be energized. For sure the engine can be run safely with the cold start valve disconnected, until the problem is fixed, as long as it can be started in cold weather. |
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