fuel delivery issue

[essex boy]

Hi Guys

1st post. Ive got a 1991 Cabriolet (Fuel Injected). Engine turns over and I have a spark. I've replaced the small pump attached to the fuel sender , replaced the air and fuel filter. I have replaced what I now believe was a 1 way valve that sits between the small pump attached to the fuel sender with a piece of Fuel hose (when i took the valve off it seemed blocked with rubber that I assumed had deteriorated over time and assumed it was just a flashy blocked connector and didnt realise there may have been a valve in there at some point.

When attempting to start the car I put my hand on the fuel pump next to the fuel tank and can feel a single pulse as it charges. I have cracked the incoming fuel line connector of the fuel filter in the engine bay and its a dry as a bone. Ive also put a clear bit of tubing between the fuel sender outlet on top of the tank and the fuel line and am not seeing any fuel leave the tank.
I've put a multimeter on the three way connector on the top of the fuel sender and it appears to be getting 12v power when i turn the ignition on.

The fuel guage works fine on the dash so I know the sender part of the electrics is good

Thinking the fuel sender pump could be the issue I rigged up a gravity fuel feed into outgoing fuel line from the tank (thus isolating the sender pump) and tried starting the engine. Nothing happened other than all the fuel dissappeared and the fuel filter is still dry as a bone. I suspect the fuel is hitting the fuel pump and then travelling down the fuel return line into the fuel tank.

Things im considering as cause of the issue and need your thoughts on -
1. Bad earth on the fuel sender preventing the in tank pump from working , although if they share the earth would'nt the fuel guage not work?
2. One way return valve thats missing from the in tank pump - Although I believe this is only there to stop back pressure pushing fuel back into the in tank pump - but happy to be told im wrong.
3. Blown fuse for the sender pump ( is there a fuse for the sender and one for the pump?) i have an online haynes manual but its useless and the fuse box has lost its cover so I dont have a clue which fuse is for what although and initial inspection suggests there are no blown ones.
4. The main fuel pump is somehow the issue (again a blown fuse? or just seized pump, or cactus relay?) However, why would this prevent the in tankpump from pushing fuel into the fuel line to the main pump? (unless i have 2 issues)
5. blocked fuel line (but again, surely the in tank pump would attempt to push fuel down the line and Im seeing nothing leaving the tank)

your thoughts and advice is greatly appreciated



Phil

[h100vw]

Jum the fuel pump relay so they run all the time. I don't believe there's a pump in the tank. That was digifant thing.
Make sure the fuel is able to get to the pump, the short pipe off the tank.
After that you're really stuck and have to split everything to see what's causing the blockage.

[essex boy]

thanks for that h100vw. Heres what i pulled out of the tank. the larger cylindrical thing I have replaced and this is what i think is a pre-pump. the smaller shinier cylinder is what I believe is a one way valve. Anyone agree?