From Ireland, help on a MB 350 slc please - Mercedes-Benz Forum

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post #1 of 3 (permalink) Old 01-20-2004, 11:21 AM Thread Starter
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Date registered: Jan 2004
Vehicle: 1973 350 slc blue.
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From Ireland, help on a MB 350 slc please


I wonder if anyone could give me a few tips regarding a car that I recently purchased. I am a very satisfied
owner of a pair of MB 190s that I have owned for the last 10 years.

However recently I also bought a 1973 350 slc V8, which I felt would be an amusing hobby. Unfortunately my local mechanic isn't very technical or intuative.

The car runs on a contact points ignition system and has tne MB fuel injection of the period. Overall it is in very good condition.

To cut a long story short I dropped the Panzerwagon up to the aforementioned mechanic for some routine servicing. This included new points, condenser, coil and ignition leads. The fuel filter seems to be a new
fitting. I took this step as the car had started to run erratically. Somtimes stalling, not always starting when hot and not always firing on all 8 pots.

The trouble is now the engine will fire up, but only runs for a few seconds before cutting out. It restarts
easily but cuts out again as before. Fuel pump seems to be working fine (as it is audible building up pressure).

Also I have ne owners manual, so exuse me for my stupidity but I can't figure out how to release the front seat backs, in order to allow passangers into the back.

I wonder if anyone out there in MB land might give me some help and advice ?


Gerry Huet
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post #2 of 3 (permalink) Old 05-06-2005, 09:53 AM
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Date registered: May 2005
Vehicle: 1974 Mercedes 450SL, 1975 Rolls Royce Silver Shadow
Location: Ireland
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RE: From Ireland, help on a MB 350 slc please

I had this exact same problem... 6 mechanics went though the list... Point, Coil, Spark Plugs, Fuel Pump, Fuel filter only to find it was actually the ECU. I cant seem to find one anywhere so that I can replace it though!
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post #3 of 3 (permalink) Old 05-07-2005, 01:04 AM
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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.
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