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Marty
Marty, ASE Certified Technician
Category: Mercedes
Satisfied Customers: 53984
Experience:  Bosch Certified Master Technician with over 35 years experience in the automotive industry.
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R107 380sl Fuel problem Car turns over,fires on 2or 3

Resolved Question:

R107 380sl
Fuel problem
Car turns over,fires on 2or 3 cylinders ,causing severe vibration of engine eventually after 3or ,,4 minutes with starter held over it fires on ,,6 or so cylinders then runs rough ,with vibrations for ,3, or 4 minutes then fires on 8 cylinders and settles down,
The last time this happened the garage changed the fuel pump relay.
Not this time
The pump runs . What can it be?
Submitted: 1 year ago.
Category: Mercedes
Expert:  Marty replied 1 year ago.

Hi, my name is***** the car run fine after you get it running on 8 cylinders? Does this only happen after a hot restart?

Customer: replied 1 year ago.
Hi Marty it runs beautifully on 8 . Hot starts are not a problem only cold starts
Expert:  Marty replied 1 year ago.

For a cold start problem I would suspect a fault with the warm up regulator. The regulator lowers the fuel pressure to richen the fuel mixture when cold. If the pressure is too high it will run very lean until it warms up. I would suggest connecting a CIS fuel pressure gauge to the warm up regulator to measure the cold control pressure through the regulator. On a cold motor it should be around 2 bar. When the motor warms up the pressure should rise to about 3 - 3.5 bar. I would also check the spark plugs and wires and cap and rotor to be sure you are not getting a misfire when cold.

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Customer: replied 1 year ago.
Hi Marry will pass this info onto my mechanic
Expert:  Marty replied 1 year ago.

Sounds good, let me know if you need anything.