300E Fuel Distributor

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jb - 29 May 2008 12:48 GMT

My 300E won't start. I have fuel pressure because if I loosen the fuel
line to the cold start valve i get a shot of fuel spray from it. So the
fuel pump is outputting. However if I disconnect one of the fuel lines
to an injector and crank the engine, no gas is ejected from the fuel
distributor. What we be the problem with that? Thanks for your help.

JB
88 300E
99 E55

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Tiger - 29 May 2008 14:55 GMT

Did you have any problem starting the car before it quit on you? What are
the circumstances that it quit on you?

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Roland Franzius - 29 May 2008 15:11 GMT

jb schrieb:

> My 300E won't start. I have fuel pressure because if I loosen the fuel
> line to the cold start valve i get a shot of fuel spray from it. So the
> fuel pump is outputting. However if I disconnect one of the fuel lines
> to an injector and crank the engine, no gas is ejected from the fuel
> distributor. What we be the problem with that? Thanks for your help.

The injectors are working continously. They spray fuel on the outer side
of the intake valves.

During cranking the injector line is closed because there is no vacuum
behind the thottle.

During start (with normal temperature at engine) fuel is supplied for 10
sec via the start valve.

With very cold engine the injector line is opened by the cold start
idling regulator by vaccum too.

The normal supply needs running engine, vacuum build up in the intake
manifold and a floating air flow sensor plate in the air stream at the
top of the fuel distributor to regulate the air/fuel mix.

Signature

Roland Franzius

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mobi - 30 May 2008 09:04 GMT

> jb schrieb:
>
[quoted text clipped - 23 lines]
>
> Roland Franzius

You just not only have to have fuel, but fuel in a certain amount of
pressure to get the motor running well. Only one cilynder not having
fuel IMHO it's not enough to have your car not starting: there are 5
cyl. more to start the motor, even after that it runs rough. Try to
remove the fuel line connecting this fuel distribuitor exit and
atthach a hose to it, maybe the metal fuel line is obstructed.
RSalles

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Jens - 31 May 2008 23:19 GMT

> My 300E won't start. I have fuel pressure because if I loosen the fuel
> line to the cold start valve i get a shot of fuel spray from it. So the
[quoted text clipped - 5 lines]
> 88 300E
> 99 E55

Just to help you in how the fuel distributor and injectors work..

The injector valves will open at certain pressure difference, and the
flow will depend on the pressure difference. On one side is the vacuum
from the particular cylinder, and on the other side is the fuel
pressure from the fuel distributor.

The fuel pressure is equal to all the cylindres (injectors), but only
the cylinder, which is in the intake stroke (intake valve open), will
provide enough vacuum for the injector valve to open.

The pressure from the the fuel distributor is controlled by the air
mass sensor plate, which will move a plunger inside the fuel
distributor to control the fuel pressure to be proportional to the air
flow. No air flow will result in no fuel pressure (flow) to the
injectors.

The cold start valve will simply add some extra fuel to the intake
manifold for a richer mixture during cold start.

In parallel to the fuel pressure control plunger of the fuel
distributor is the EHA (Electro Hydraulic Actuator), which will fine
adjust fuel pressure and thereby the mixture according to control
signals from the ECU.

If this is defective, it may provide way wrong mixture and thereby
preventing starting. I had this problem with two different EHA's. Once
replaced with a good one, it started right away.

I could of course also be other things, but I hope the explanation
will assist you in the troubleshooting.

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