on this vehical it starts it runs but out of no where it turns off like it ran out of fuel..it has 2 fuel pumps..i can hear them pressurize the system...Anyone ever encounter this sorta problem..If u have.. please let me know also any and all suggestions will be appreciated.

 

something is loose like electrical components.

check the fuel pump relay and over voltage protection relay for dirty contacts and corrosion.

if the fuel pump makes too much noise, it needs replacement.

 

Thank you Sleepwalker for such a quick response...Another question is Can the fuel pump relay & over voltage protection relay be tested to be sure id they are damaged? the voltage protection relay is that the unit by the battery?

 

the way i see it, your problem is intermittent. therefore they are not damaged, but gets faulty on a certain condition.

the relay and OVP are electronic parts and the only way to test it accurately is to install a good one to test.

the good tools for testing is the parts itself.

 

You are correct the units themselves(relay & ovp) are corrosion free and in great shape ..physically...Seems the vehical after fully warmed up will turn off while driving and turns itself back on before i can turn ignition key...any other suggestion will be appreciated

 

you're a mechanic and trying to fix this car...right?

if you suspect it's the fuel pressure problem, try installing the pressure gauge on it and road test the car.

observe if the pressure goes down when the problem occurs.. if not, you can eliminate this test and proceed to other things. at least you won't spend more time about the fuel suspicions.

 

I have a 1988 300 SE that gets driven once every few weeks, it was running fine until it started to stall at traffic lights, but then after cranking it would start, I figured it needed new spark plugs, replaced the spark plugs and ran fine for few months and then it did the stalling again, now it will crank but will not start, so far I replaced the fuel filter, distributor cap, coolant temperature sensor. I checked the fuel pump relay and its fine, there is spark going to the spark plugs, and I believe the fuel distributor is fine also because the cold start injector is working, the only thing that I am not sure about is the timing for the spark, I read that the crankshaft position sensor is what gives the ignition module the signal as when to fire the spark, how does one check to see if the crank position sensor is bad other than reading the resistance on the end that plugs into ignition module?
is there any other sensor that gives the ignition module a signal to determine the spark timing?
any help is appreciated.

 

the other way to check it is to use the multimeter.

set it to 10 volts a/c.

crank the engine.

normal reading is 3.5 - 5 volts a/c.

 

If u have read this topic u can see that I too had this problem...Replace everything u have and still same problem ..finally gave up and took it to the shop(mercedes shop)...they found the problem..I t was the crank positioning sensor....P.s. I had every problem u are experiencing and they finally figured it out...When i spoke to mechanic his first thought was the fuel relay(the one by the battery) or the crank position sensor...after all test he pinned it to the crank sensor. Hope this helps.

 

Thanks
well I have subscribed to alldata for my 300 SE and alldata has good help in explaining what to check and eliminate the areas that may be causing the problem, the only thing I don't like about alldata is the tools that they use to test these sensors, the tools they mention are available only at dealers and not a regular digital meter, and I have subscribed to the do it yourself section of alldata, yet most of the test equipment is not available to people.
the only thing that was left that I suspect in my car is the crank position sensor and I took the sesnor with the cable out, other than checking the resistance on the end terminal I can't test to see if the sensor itself is faulty, the resistance checks ok with specs, I will ask a Mercedes repair shop if this sensor is what controls the ignition timing before I buy a replacement.
your reply is much appreciated.