engine starts and dies right away

[tecqboy]

Any of the fan belt driven devices ( water pump, p steering, alternator, air conditioner compressor, etc ) on the front of the engine could shriek if you have a bad bearing or if the fan belt is too loose. The air pump / injection pump only runs when the engine is cold. It gets a signal when the engine warms up to dis-engage its' clutch. So, check the fan belt tension.

[blueshield11]

fan belt tension is okay

[ctaylor738]

First of all, there is no "injection pump" on this car. There is an electric fuel pump in the rear and a regulator that maintains pressure at all times the engine is cranking or running. Based on the volume of air (measured by the deflection of the sensor plate), the fuel distributor sends the correct amount of fuel to the injectors. Excess fuel is diverted back to the tank.

Alldatadiy and wikipedia have decent explanations of how this all works. If you don't have a basic understanding of the system, you will not be able to diagnose and fix problems.

It sounds to me like you're not getting fuel to the cylinders. The cold start valve may be delivering a short puff which will allow it to fire, but then it gets nothing from the injectors so it dies. You might also have a bad fuel pump relay, causing fuel to be delivered while cranking, but not when the key is released to Run.

Try a couple of things:

- Remove the fuel pump relay and jumper 30 to 87 on its socket and make sure the pump is running. If if is, then try to start the car. If it starts, you need do further testing to find out if the relay is bad or missing "tach" input.

- If the pump runs but the car still won't start, remove the air cleaner and have someone crank while you push the sensor plate down just a little with a stick. This will cause the fuel distributor to provide more fuel and may be enough to start the engine.

How these tests turn out determine next steps.

[blueshield11]

With injection pump I meant "air pump", and I thought I have read that it was also called injection pump.



I will check the fuel pump (I think it works) and I will do the test with the sensor plate. But, don't mind me asking, I will try to attach a picture here to be sure I know what you mean with the sensor plate.

[Gurunutkins]

yes that is the sensor plate, here are some pictures from one I am currently working on the pictures are of the top of the engine, the sensor plate the throttle plate the idle air adjuster screw and the fuel distributor on top of the air intake. This way we all know what we are talking about, much easier! if the pump is working you will feel the change in pressure on the sensor plate so as I said in the original post earlier test the sensor plate when the car has stood for at lest 12 hours and then just turn on the ignition and let the pump run to pressure the system and you will feel the resistance on the sensor increase. also as in my earlier post just push down the sensor a mm or 2 with a stick (as Chuck says) or risk a friends fingers and see if she starts. report back whatever you find
cheers
Barri

[ctaylor738]

THE FUEL PUMP RUNS WHEN THE STARTER IS CRANKING OR WHEN THE ENGINE IS RUNNING. IT DOES NOT RUN WITH THE IGNITION SWITCH SIMPLY TURNED TO "ON" - THAT'S WHY YOU NEED THE JUMPER.

The reason for this is safety. If the car is in an accident with unconscious passengers and an stopped engine, the last thing anyone wants is a running fuel pump.

[blueshield11]

thank you all for the information. I am going to do that today and will be back here to give you an update.

[Gurunutkins]

Chuck is 100% right about the pump only working with the engine running or the jumper, but if you are working by yourself and dont know where the fuel pump relay is you can defeat the safety interlock by pushing down on the air flow sensor plate. the safety interlock is the air flow position sensor (the blue green connector in the last picture between the air flow sensor plate and the fuel distributor) if the ignition is on and you push down the plate you can feel as the pump comes on and pressurizes the system. Its also useful to know if you are testing flow rates as you can stand (if you are alone) in the engine bay with the incoming pipes disconnected and "switch" the pump on by pushing down the air flow plate
cheers
Barri

[ctaylor738]

The 380's don't have the safety switch. The pump will not run unless the engine is starting or running. You have to jumper the relay, period.

[Gurunutkins]

Thanks Chuck, I did not know that about the 380. does the later 560 have it?

[ctaylor738]

I believe that the safety switch was only used on the older units with the cast iron fuel distributors and sometime around 1980 those were phased out. So the 560's do not have them.

Actually, they were kind of handy, just pull the connection off and no need to bother with the relay.

[blueshield11]

@ ctaylor738 : Please come to my place .

What a terrible car. I am trying to find out how this car really works.
Was looking on the internet for animation of the engine. I saw a lot of Mercedes cars on Youtube, but not what I was looking for.

I was not able to do the tests today, tomorrow will be The Day for that.

Get back to you with update.

[450slcguy]

Originally Posted by blueshield11

What a terrible car. I am trying to find out how this car really works.

Actually they are great cars, you just need to buy the Mercedes repair CD if you really want to know how the car works. Your stumbling in the dark without it.

[aam]

If your idle valve clicks.
And you get gas at the engine.
I would open up the distributor.
Check the cap, especially the rotor they been known to crack and brake.
This all can be done with out spending any money.
In order to have ignition you need three things.
1, gas.
2, air.
3. electricity.
Regards,
aam.

[ctaylor738]

Last week I was down with the flu and sort of over-achieved on advising another guy with K-Jet starting issues. This may fill in some of the blanks for you.

Help!!!!!! Ideas Why It Does Not Start