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I've just searched the Type 3 and the combined K(fuel system) manual to find the reference I was sure was there, and I can't find it. I was also reading through the carb pages, and I think I've maybe mixed it up in my mind with the twin-carb accelerator pump adjustment procedure, which involves changing spring tension with different thickness washers. DOH! The Type 3 manual does describe adjusting the diaphragm spring coil-spacing to change the pressure, and also advises that the push-rod stroke changes the pressure. I remember years ago there was a run on the flange gaskets as people were told they could reduce fuel consumption by putting an extra gasket or two under the pump. The extract reads:- "The pump pressure is determined by the adjustment of the push-rod stroke and the diaphragm spring tension. The push-rod stroke is adjusted by adding or removing flange gaskets. ... If the push-rod adjustment does not give the desired result replace the diaphragm spring. Otherwise, if the pump pressure is too high, the intermediate turns of the spring may be coiled closer together, and if the pump pressure is too low they may be stretched apart." I suspect the push-rod stroke wouldn't do much to make a Type 1 pump give the right output pressure for a Type 3, though the opposite might be true. Incidentally, the 1965 manual mentions 4.5 psi, so maybe it was increased to 5 psi for the 1600. The washer (was it 1.5mm?) added by Ben gave an extra 2psi ISTR. Some people have reported using a Type 1 pump without any apparent problems. If you get problems, I can't see a washer to increase the tension enough could do any harm. VW also say that under normal operating situations the diaphragm moves only a fraction of a millimetre. Dave. UK VW Type 3 & 4 Club http://www.hallvw.clara.co.uk/ ------ ------------------------------------------------ To unsubscribe, E-mail to: <type3-off@vwtype3.org> For more help, see http://vwtype3.org/list/