Injection Pump question (another one)

[handyandy]

Hello all

I usually restore old lotus and other british cars but am currently trying to get a 250SL to run again for a customer of mine, (it hasn't run for nearly 10 years) having cleaned out the fuel tank feed and return lines which were completetly blocked, freed of the fuel pump, the injector pump is giving me trouble.

I have read all the very useful posts on this site and have made a tool to remove the check valves (12x1mm pitch thread by the way) having eventually freed of the plungers and the rack It took me a while to work out the the check valve centre was supposed to move as they were seized totally solid on this car!

I have got them freed off but I still cant get fuel presure out off the top of the pump, It may be that I need to turn the engine over for longer but I have one question first

Is the centre of the check valve (the actual valve shaped bit) opened purely by the fuel pressure or is the piston supposed to lift it by physical contact? if the latter is the case does the cylinder around the plunger lift out without further stripping of the pump? so that i can check if there is any debris stopping it sitting lower as my plungers do not clear the top of the cylinder.

Sorry for a long and convoluted explanation! hope somone can supply an answer so taht another car can live again

Andy

[al_lieffring]

Yes the check valves are popett style valves and open only by the fuel pressure.
I usually use a very fine valve laping compound to clean up the seats to where they will seal. 

[ja17]

Hello Andy,

Make sure the electric fuel pump is running and the 19mm fittings on top the fuel pump are torqued to 18 ft lbs. before cranking. Crank engine at full throttle until fuel emerges from the IP.   Only a very slight amount of fuel will emerge on each stroke.