PeachParts Mercedes-Benz Forum - View Single Post

dpetryk · #3 09-09-2001, 11:30 PM

I have actually "cured" a faulty fuel distrubutor. Here is the story. I purchased a 87 420sel at a price i could not refuse. Then began the work of fixing all the gremlins that the car had collected while sitting undriven for 2 years. The car was a "low maintenance" vehicle for the previous owner. One of the problems was that the lambda control unit was unable to hold the mixture at the right value. I replaced the fuel mixture control regulator (located on the side of the fuel distributor) without results. New oxygen sensors, a new lambda control unit and still it was not working correctly. I measured fuel pressures and checked the injector spray patterns. I had eliminated everything except the fuel distributor, primarily because of the cost for a new unit was $900. I was told that they are not repairable or adjustable. So I was faced with two choices, attempt a repair on the fuel distributor, or replace it. SO before I open it up, I took it off the car and used a can of "brake clean" to wash out the unit. I did get some residue out of it that seemed at the time to resemble varnish, or so I thought at the time. I forced cleaner thru every orface in both directions all the while moving the plunger in and out. I had heard stories of an old mercedes trianed mechanic who made a brew of injector cleaner and ATF and he would soak the distributor for several days in this solution and evey so often move the plunger. It was said that he "cured" 7 out of 10 or so. I also noticed that there is a small screen located at each of the 8 fuel line connections. These screens could get plugged up and prevent fuel from flowing. The unfortunate thing is that there is no way of replacing these screens. I reasoned that the only way was to force solvent in the opposite direction to dislodge the particles and hopefully wash them out. Prior to washing my distributor, I examined the screens using a microscope and sure enough there was stuff in the screens. But not enough to block fuel in my case. After a through washing, I replaced the fuel inlet screen and put it back on the car. To my surprise, it worked as it should. The lambda control unit now had enough authority to keep the mixture at the right value. Fuel mileage went from 10-12 MPG to 19. I was happy. So try to wash the thing out. It worked for me.