As soon as I took the old one off the pieces fell out of it. Thanks to those who helped me diagnose. It was coming and going intermittently which apparently is a telltale sign of check valve failure.

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1981 300TD
2005 C55
2004 E500
1999 ML430
1992 400E
1998 C43
2001 SL500
1988 300SEL
1986 190E 16V
1991 190E 2.6

Could you have gotten the pieces out without removing the pump, you are talking about the check valve on top where the line comes out, yes?

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

I just pulled the check valve out. I used a magnet to get the spring out and a vacuum to clear any other debris that may have been in the orifice.

After I saw it I thought I may have to pull the pump to clean it out but it works fine now, not going any further at this point.

__________________
1981 300TD
2005 C55
2004 E500
1999 ML430
1992 400E
1998 C43
2001 SL500
1988 300SEL
1986 190E 16V
1991 190E 2.6