1986 e30 325i Baur cabrio fuel feed issue

[Avinit4]

Hi people, Firstly does anyone know what the Damper and the Damping Unit on each side of the fuel pump actually do? Can either become faulty & cause engine to just start, but runs rough like its missing, wont rev up and just dies when you try?
My problem is: Everything was spot on & started instantly on the key. Had replaced the return fuel pipe and tested while still on axle stand. It started & run pefect.
Took off axle stand, got in it and sudenly wont start or run properly? I'm proper screwed trying to work out why as didnt touch anything related to engine.
My son jacked it up toyake off axle stand & accidently pushed damper & pump up at same time. Have changed pump but made no difference, hense my question about the damper & damping unit? Any help gladly recieved. Cheers

[zaust]

Did you take the fuel lines off the rail ? Possibly put them back the wrong way round.

The dampers are also filters. By pass them one at a time and see if there's a running difference.

[Avinit4]

I didn't take fuel lines off the rail.
Why its so puzling is that everything was running fine when on the axle stand but not when taken off axle stand.
As car had been standing for a year Im thinkin possibly ether the pump or injection relay so am about to replace both. Failing that I'l bypass damper as you sugested. Thanks for your help

[Avinit4]

Just to update you zaust, it was the injection relay (5 pronged one) altho I replaced them both anyway. Back on the road at last