BenzWorld Senior Member
Date registered: Jan 2005
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RE: From Ireland, help on a MB 350 slc please
Hi guys,Before you start messing with the ecu etc,start from the beginning again.
check all spark plugs,check the points,check the plug leads for too much resistance,examine the ballast resistors and clean the terminals so there is zero corrsion.Replace the coil because it's 30 plus years old and thse things have finite life,even on mercedes.
replace the fuel filter,it may look clean ,but if you didn't replace it in the last 2 years ,it is now due.
If you can manage,drop the fuel tank,there is a large bung in the bottom,you will need to either borrow or fabricate a tool to undo it.i made mine from a bolt welded to a 2' long peice of 2" x 1/2" thick steel and I belt it with a hammer to loose the bung.
The bung has a filter in it,either buy a new bung or get the old one ultrasonic cleaned.
Replace those rubber hoses from the tank to the fuel pump,there will three under there,they will all be shot by now.
clean the tank out or get it boiled by a radiator or engine specialist.Make absolutely sure the smaller of the two fuel pipes is clear,thats the return and it always corrodes for some unknown reason.
Reinstall your tank, hook up your new hoses and filter.
You will now need a guage to measure the fuel pressure.connect it to the line at the front of the engine that runs to the start valve,thats an injector by itself on the left hand front of the intake manifold.
at the middle of the engine,in the rear is a fuel line that runs back to the tank,blow air down it to ensure it is clear and hasn't been blocked by rust or squashed under the car.
OK,now make sure all fuel lines are secure,no leaks etc.put about 5 liters of petrol in the tank,and start the engine,you should have 28-30PSI on your guage,let the engine idle and if it cuts out check the pressure,DID it rise or drop off?.If it rose,there is a blockage causing an overpressure ,if it dropped,you must check that you are getting a minimum of 11.5 volts at the fuel pump terminals.
If so ,the pump is worn out and needs replacing.Any 116/123/126/114/115/ bosch injection pump will be OK if you have to get one from a wrecker.
Do this in the order i have mentioned ,you should be OK,If it now contiuesa to run ,but runs rough,the injectors must be removed and ultrasonic cleaned.Pouring stuff in the tank won't clean the electronic injectors.
It all looks complicasted but it's stone age technology today and your ECU wil be OK it's extremely rare for one to fail.