My new 83 280 SL

[zakkkk]

I recently purchased a nice euro 107 with 107 K miles that spent it's life in Fla. Original dark blue paint and plaid interior, well maintained , 2 owner car with full orig manuals and import and service records back to the beginning, auto tranny. I am enjoying getting to know the car and driving it.
There are a few things I want to address and would welcome advice.
- Starting: If I leave the car for a week the fuel seems to drain back towards the tank because it would take a while for the engine to start and when it did start it would miss and tumble for a while that run normally. If I turn the key to on position and let the fuel pump run for 20 seconds or so then crank the starter the engine starts like a shot on half a crank.
But now with the warm, humid weather the car starts poorly and sputters for a while. I have to keep using the gas peddal to keep it from stalling for 3 minutes or so- then it runs fine but with a low idle until I drive it a mile or so then perfect.
I adjusted that large flat head screw that adjusts the air mixture and increased idle speed and it seemed to help, but I think there must be a real solution.
The alternator light glows on the dash when I turn on the headlights, so I know to check power output under load. If I have to replace/rebuild the alternator should I increase the greater output with a stronger alternator?
The seller, an elderly Fla gent said to me... it's a different car at 4500 rpm's and I didn't know what he meant. But now I know.That M110 engine is amazing- even above 3000.
I would love to have this baby running like a clock.
Any guidance is appreciated.
thanks
jz

[rowdie]

Could be the regulator and not the alternator. No reason to try and find a higher amp alternator unless you plan on major add ons with huge amp draw. I can leave my 280's sitting for weeks and they start right up. Only thought on that is the cold start valve is not working.

Sounds like a really nice 280. The M110 is a really good engine.

[nobby]

The AAV might be stuck closed. It should be open when cold and gradually close as the engine warms up.

There is a balance between air and fuel when cold and when hot. I'm still fiddling with mine but MY last step is the AAV and it is in a horrible spot on the M110 which is why I'm living with it.

[rs899]

I honestly have not had any fuel system issues on our 380SL, so I don't know too much yet on the K-jet. But, there is a check valve on the fuel pump and an accumulator next to it that might be an issue.

There are many sources of K-jet theory on the 'net. One place is the sticky section of BW R107 forum (where we all hang out)( hint)

You in Florida now? That car sounds familiar on CL....

[meltedpanda]

I would suggest purchasing this book

How to Tune and Modify Bosch Fuel Injection , by Ben Watson
owning these ol gals require a good step by step book for the bosch systems ( all systems) . They have to be diagnosed in sequence, and this is a good book to guide you. ( My pages on the Djet are worn out lol

[zakkkk]

Thanks gents,
I am in northern NJ. I actually found the car for sale in MBUSA Star mag. I am unsure if it was listed on CL.
The car was sitting for a while and undriven due to illness. So the more I drive it the more normal it runs. My starting issues are only on the first start of the day. After that the engine starts perfectly.
May I ask what an AAV is ? I am only capable of theoretical mechanical repairs and lack hands on experience. There are a couple of old school MB guru's up here that I use. I will pass your comments on to them.
Is a symptom of a bad cold start valve poor starting in hot weather only?
I am surprised to see how well equipted these euro 107s were. Mine has factory A/C, power windows and heated drivers seat. I think it must have been purchased with a gray market sale all lined up because the sale to US buyer was not long after the actual factory build date of the car.
Anyway, all good and thanks for comments.
jz

[zakkkk]

I forgot to mention that the steering sometimes feels tight and sticky but sometimes it feels right on. I know the 107s are not known for their steering delicasy.
Fluid is full and clean.
My FSH shows a steering box rebuild and fluid change about 10K miles ago by former owner. Might the bow be too tight? Are there adjustments that can be made?

[meltedpanda]

could have air in the lines, especially if it has sat for awhile, seems like there is a post here somewhere on that
AAV = auxillary air valve
here is some basic info
K-jetronic- K is for continuous, the system is mechanical with parts that control cold start
and idle that are electrical or electrical with vacuum assistance.
The amount of fuel is controlled in proportion to air flow to give the correct
air- fuel ratio. Air flow is measured by a metal plate in a cone shaped cylinder.
A plunger is connected to this plate. The plunger controls the pressure in the fuel
metering unit. The pressure is produced by the fuel pump operating at a specified
pressure particular to each vehicle. There is a differential pressure controlled by
the plunger. This differential pressure operates the injectors. The greater the air
the greater the differential pressure, the more fuel that is injected. The fuel is
continuously injected rather than with each intake opening.
K-jetronic with lambda- operation is the same as above with the addition of a lambda
(oxygen sensing). The lambda was added to further help the emissions of the
vehicle. By sensing the oxygen in the exhaust, the lambda will adjust the
co content.
1982 - 1983 Cold Start
1. Turn the ignition key to start. The starter operates and the engine turns drawing air into
the intake. This air moves the plate in the air sensing unit. When the plate moves in the
upward direction a micro switch is energized. This switch applies a ground to the fuel
pump relay. With the switch in the start position, a RD wire applies a positive voltage to
the fuel pump relay. The relay then closes and power is applied to the cold start valve.
2. The cold start valve allows additional fuel to be applied as needed to help start the engine.
The cold start valve stays on for a short period of time. This is because of a thermo switch
in the circuit. The thermo switch controls the amount of time the cold start valve stays on.
3. The warm up regulator is also energized. This valve is electrically controlled. The valve
gets its power from pin 30 on the fuel pump relay. Pin 30 also applies power to the
auxiliary air valve. The air valve is also electrically controlled. Power is received from a
RD/WH wire from pin 30 on the fuel pump relay.
The warm up regulator will control the fuel pressure during cold start and during warm
running. Fuel pressure is lowered during the process of cold start to allow a richer mixture
of fuel to be injected. The auxiliary air valve will allow a small amount of air to by pass the
throttle to help in cold start.
4. When the engine starts the cold start is turned off and the warm up regulator continues to
control the fuel pressure during warm running.
5. Hot Start: When the engine is started while it is warm the cold start valve is not turned
on. The thermo switch controls the time the cold start valve is on and when it is to turn on
and allow additional fuel to be applied. The warm up regulator will continue to control the
fuel pressure during warm running of the engine. Fuel pressure is raised to allow a leaner
mixture.
Note: You will find that the cold and hot start operation does not include a thermal valve
and a vacuum line attached to the warm up regulator. In 1982 the thermal valve and the
vacuum lines were not used.
8.3

[meltedpanda]

out of an old Porsche manual but basically the same Bosh components in MB


Engine will not start Warm
1. Air flow sensor plate not adjusted correctly:
Remove the boot and the air filter and check the position of the plate as compared to the
barrel. The plate should be even to the bottom of the barrel, a tolerance of +/- .020 is
allowed. You can adjust the plate: 1973 ½ - 1975 by bending the clip and 1976- 1983 by
adjusting the screw with an allen screw driver. The screw driver is put m at the top of the
mixture control unit through a hole.
2. Fuel pressure is not correct:
Check fuel pressure at the fuel pump.
3. Cold Start valve leaking:
Check the cold start valve by removing the part from its location. Leave the fuel line
connected. Remove the connector, place the valve over a container and apply voltage to
on of the connectors and a ground to the other. Look for a coned shaped injection of fuel.
Turn off the power and wait a few seconds. Watch for leaks. If either of the above does
not work, replace the valve.
4. Vacuum Leaks:
Carefully inspect the complete engine for any cracked or worn hoses.
Look for connections that may be loose or have come loose.
5. Control Plunger in Fuel Distributor binding:
Check this by first depressurizing the fuel system. Do this by relieving the fuel pressure at
the warm up regulator. Remove the fuel filter and carefully move the plate up and down.
This movement should be free and with no binding. If you detect binding, replace the fuel
distributor with a rebuilt unit.
6. Fuel Accumulator and/or Fuel Pump Check Valve:
These hold pressure in the fuel system.
7. Fuel injector Clogged:
Pull the injectors and inspect for correct operation. Apply power to the fuel pump,
jump the wire terminal numbers 30 and 87a. Caution fuel will flow from the injectors
when the air flow plate is moved in an upward direction. Check for correct operation.
8. Control Plunger in the fuel distributor binding:
Remove the air cleaner and carefully move the plate up and down, do not force the plate.
If it binds investigate. If it is not simple to repair replace the unit.
9. Idle speed, Ignition Timing, and mixture out of tolerance:
Check and adjust all of the above.
10. Faulty Ignition System:
Check the ignition system. 1973-1977 check point gap .016, correct plugs see chart,
Condition of cap and rotor, 1978-1983 check for a distinctive hum in the CDI with ignition
on in engine compartment, (if no hum the CDI may be defective) CDI is the ignition
module located on the relay panel in the engine compartment left side.