Checking your fuel distributor

The fuel distributor that you see in the pictures is a fuel distributor from a 400 i. After the fuel pump (in the fuel line) you have a fuel filter. This fuel filter should filter the dirt out of the fuel system. Unfortunately after (in my case 30 years) the fuel distributor is getting dirty.

You can’t see from the outside if a fuel distributor is dirty. The dirt in a fuel distributor will restrict the fuel that is coming out of the ports. Because the dirt is often not spread around the fuel distributor equally the fuel which comes out of every port will not have the same flow.

The best first indication you can get is by checking the fuel filter in the fuel distributor itself. Under the banjo bolts you find (in case of a 400 i) very small fuel filters. You can remove these filter (and re use these filters) by carefully turning them with a small screw driver and pulling them out. If these fuel filters are dirty the fuel distributor will be dirty as well. These small fuel filter avoid that dirt from the fuel distributor “flows” to the injectors. The lower part of the chamber is often not dirty but because of the small opening to the fuel lines the dirt is in the upper chamber.

What you can do is measure the fuel flow of each port. You attach to each port a container and measure the fuel flow. The fuel flow for the ports should always be equal to the other ports in case of a K Jetronic. If there are (big) differences the air/fuel mixture for each cylinder will be not near its optimum (lambda = 0,95) and the engine will lose power. You can measure the flow by letting the engine start with attached containers. You can also disconnect the signal cable to the starter remove the black air duct and move the air sensor plate by hand with a magnet. I case of a 400i you can take the fuse or relay out from the left hand fuel pump to test the right hand fuel pump. Remove the relay of the cold start valve or disconnect the signal cable of the (two in case of a 400) cold start valve(s) to avoid this valve spraying fuel in the inlet when you are testing the flow of the fuel distributor.

With the containers attached and in case the engine isn’t running the plunger in the fuel distributor should lock the slits and the flow to the containers should stop. If you have a unequal flow from each port and an old fuel distributor the only way to clean it is by bringing it to a specialist of cleaning it yourself see the other thread

If you have cleaned your fuel distributor you can test it the same way. Test the flow from each port and test if the plunger closes the port if the air flow plate is in rest position. You can build the flow metering and containers yourself or send e-mail. I offer them on ebay.com for sale as well. The price depends on the number of cylinders. When you remove the blue screw on to of the container you can use the containers to check the injectors as well. An injector has exactly the same diameter as the blue screw. If you think that you have a bad injector you can test it with a container on a running engine.
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See the picture. The relay's of the left side fuel pump and cold start have been removeds for testing. The siugnal cable to the starter is removed (can't been seen on the picture)
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