QuestionQUESTION: Hi really hope you can help, my merc. starts perfect from cold but once hot it takes around 4 cranks to start i have changed most things including fuel pump,leads plugs etc. hope you can help.
ANSWER: Hello Chedeen,
Do you mean 4 revolutions or 4 stop and restarts. There is a possiblity that you are getting some fuel vapor lock because of the higher temperatures. Expecially if you have ethanol laced fuel.
Heat build up increases when the vehicle stops; fuel in the lines get very hot and percolate inside the line causing vapor to form. It takes the fuel pump a moment to bring fuel from the tank up to the fuel rail an drive the vapor out of the injectors.
During the multiple attempts, you finally get liquid through the injectors and the vehicle starts.
I heard stories of the old days when vapor lock developed, wooden close pins were clipped to the steel fuel line where it came to the carb. There was enough head sink to take the fuel away and slow or stop the boiling inside the line.
Also, make sure that your electric fan is operating properly. It is thermostatically controlled by the radiator temperature. The cooling system need to be in good condition to keep the engine temperature down.
Make sure you have the proper antifreeze mixture installed. The fan should also run full time when ever the AC unit is working.
A higher octane fuel could also help with the temperature situation. If you can find non alcohol fuel switch to that.
Also purchase a bottle of Techron in the black bottle and add this to the fuel in accordance with the directions.
Good Luck and let me know how thing go.
Rob
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QUESTION: This mercedes is a 1991 190E 1.8 fuel injection and takes exactly 5 start and stop cranks before it starts if left for more than approx. 3+ minutes after switching engine off
You dont have to touch the gas pedal to assist the engine,it will just start after 5 cranks.
When i ran a fuel pressure test on it by putting the gauge
between the fuel distributor and the fuel delivery line when i switch the igntion on to activate the pump the test gauge reads around 3.4 bars but then takes approx. 1 minute to drop to 0. so iam thinking the fuel pressure is not holding long enough, but cant seem to find the problem for the last year i've replaced fuel distributor,fuel pump,fuel pump relay,fuel pressure regulator with used parts and new distributor cap and rotor brush and fuel filter.
but i find if i block off the pipe that comes out of the fuel accumulater and back to the tank, it will hold the fuel pressure longer and the car will start not perfect but a lot better,what could be the problem if i cant solve it i'll have to sell it.
AnswerChedeen,
A loss of fuel pressure is probably caused by leaking injectors. Here is a web address that may explain the condition and a fix. Although it is not your model, and a cold start problem, I expect the cause is the same. The injector opening parameters are out of bounds.
Read and let me know what you think.
http://autorepair.about.com/library/faqs/bl283h.htm
Rob
