Volvo Repair: volvo fuel pump, size thread, check valve

Question
QUESTION: just replaced fuel pump on 81 dl  the book mentions a check valve, found it on the old pump but was not on new pump.  couldn't transfer part of old pump (different size thread) & what is, what does the accumulator do?  should that also be replaced?  seems to be running fine after replacement

ANSWER: Tom, basically it helps hold the pressure.  What kind of pump did you put on it?  Roger

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QUESTION: replaced with NAPA replacement for the car.  everything bolted/ connected like the original just no check valve.  With over 200,000 miles was not sure if the accumulator should just be replaced. ( also replaced fuel filter )

Answer
Tom, There is your main problem. Those pumps are nothing but junk.  They are universal pumps and do not have the sufficient PSI to run a CI injection system Properly.  Get a bosch replacement.  The check valve holds the pressure when car is shut off.  Roger