Engine running rich

[gnj588d]

Mercedes enthusiast. [monthly magazine] run a quarterly classic magazine,this month a very nice 230 on the front cover,and some really interesting stuff inside on sale know.Cheers.Mike.

[Anfinn]

I bought that magazine. In the article about the Pagoda it mentions that a common problem in the fuel system is a stuck "float".
It could cause the engine to run rich or lean depending on the position it was stuck in.
As my (280) engine is running rich, - and the pump is adjusted as lean as it will go -, can anyone shed any light on which float it is referring to??

[Jordan]

Anfinn, they are probably referring to the WRD (warm running device) on the injection pump.  There is gobs written about it on this site.  Just do a WRD search.  They can stick which will cause the engine to run rich or lean, depending on where it is stuck, just as the article mentions by the sound of it.

[Anfinn]

Thanks.
I have checked the WRD earlier, and it moved freely. Could check it again..

[mdsalemi]

I don't have the magazine so I don't know what float they are talking about.

The fuel delivery pump, at the back of the car, pumps a continuous flow of fuel at specific volume and pressure, in a continuous loop.

Out of this continuous flow, the fuel required for operation is taken by the fuel injection pump; the rest is returned to the tank via a return line and the "flower pot."

There are three rich/lean adjustments (correct me experts!); one for idle outside the pump, and one for mid-range and high-range inside the pump.  The inside adjustments have to be made by removing a plug.

Is it possible you have a leaky cold start injector?  Are you rich at idle (less than 1,000 rpm); midrange (1,500-2,500) and high range (2,500+)?  Or just one of those?

Have you done the "Blacklick CO test" to determine this lean/rich mix at all speeds?

Sometimes, as the case was with mine, the process was iterative; adjustments in one area required re-adjustments in another.

Also, I believe these pumps "wear" to rich; so maybe you have some worn parts in the pump and it is time for a rebuild?

[Anfinn]

Thanks Michael,
I'm not sure if it is rich over the whole RPM-range, but certainly (?) at idle. It idles at more than 1000 rpm, - about 1200 if the rev counter is correct.
It has only had one statutory check since I restored it, and I was then told that it was running too rich. CO too high.
I don't know how to adjust inside the pump, but I can read up on it.
The external adjustment on the pump is turned as lean as it will go without the adjustment screw starting to turn with the pump.

[mdsalemi]

Note, this topic should be renamed/relocated to engine topics.

Anfinn, also possible that you have the WRD with too many or too thick shims; this causes an overall rich condition I believe.

1200 is way too high for idle, in my opinion.

Has anyone altered the system here? Sounds like you should go to midrange on the idle rich; adjust linkages per "The linkage tour" and go from there.  Running anything like this either all the way lean or all the way rich doesn't sound right to me.

It could very well be that someone made adjustments in the wrong place at one time.

[ctaylor738]

One of the most basic checks is to make sure that the linkage lever on the pump is against the stop in the idle position.  If it is even a small amount off it can richen the idle beyond the capacity of the adjustment.

[twistedtree]

Just to ask a stupid question...... Could the "230" refered to in the article be a carburetted model that has a fuel float, and have no bearing on the injected models?