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Testing the K-Jetronic system

Started by Max-NL, 03 April 2016, 04:58 PM


So today we were supposed to replace the pump assembly. Bought a new accumulator, hoses,tank strainer, feed hose, clamps etc. The only thing we're not replacing are the brackets and the pump.

Removed the feed hose to the damper cage, drain the tank and then wait. This went well and when the feed hose began to drip I decided to remove the assembly. For some reason I decided to remove the bracket from the rubber buffers. Of course the nuts were rusted and after a quarter turn the rubber split, and we did not buy those so now we can't install the assembly. Bon, not the end of the world so we'll wait for them to arrive.

So we moved on and removed the feed hose and the strainer. The old strainer actually looks nice. A bit discolored but clean. Installed a new one, installed the new feed hose and that was it for today.

We'll continue Monday to remove the rust around the bracket while we're waiting for the buffers to arrive.
1971 R107 350 SL
1972 W108 280 SEL 3.5
1975 W116 280 S
1975 W116 450 SEL 6.9 #140
1977 W123 230
1992 W124 230 CE
2001 Ducati Monster S4


I'd say the fuel pump is the most likely candidate, if the supply pressure or delivery volume is that low, it is unlikely to be the accumulator, strainer or filter. I'd check the delivery volume (spec in the M100.985 combustion section) and the get the pressure correct before changing anything else further down the line. The pump acting against the hydraulic/hydrostatic back pressure of the distributor and the accumulator is what creates constant, stable system pressure.

Other likely candidates for problems further down; the fuel distributor, injectors, mixture and least likely - the warm up regulator.

Rubber buffers are available from Mercedes Classic for a couple of dollars. If you're restoring the car it's a good opportunity to send the brackets for Zinc plating (with yellow Cr6+ passivation) as they are probably showing rust or signs of corrosion by now.
1979 450 SEL 6.9 (#5532) - silbergr√ľn metallic