In praise of Delphi fuel pump
 

I have to say I am pretty impressed (so far) with the Delphi fuel pump! It is smaller than the TI, which had me a bit worried at first but seems to be working VERY well. The check valve is holding better/longer and I am noticing quicker starts, it's pretty much silent and hopefully the carbon commutator proves to be a bonus and I live long enough to tell about it! ;)

I had good luck with them. My premium Bosch was DOA found out too late to exchange grrrr.

Maybe less praise today after fixing burnt wiring connector! ;( Probably partly my fault for not putting any contact grease on the connector when I installed the pump a while back but power wire connection now failed. The wires (and likely the contact pins) don't look like they are probably the best quality, or it could be 20 year old connector with no contact grease or some combination but had to deal with that today. Really lucky that the car quit in the driveway though! ;)

Dang, next on preventative maintenance list: new fuel pump.

Between 20 some year old connectors with maybe seals that are no longer that great and maybe the mating surface on the pump side isn't perfect, I would at least definitely use some contact grease. It seems to be a known issue even from the factory and sooner with the E70 so I went with wiring everything direct on the E53, you need to make sure you get a good seal on the wires though or you'll get a CEL for tank leakage! Tank leakage code might also be a hint to maybe having a melting connector issue! ;)

Did you replace the syphon side too? I'm debating on doing both sides or just the fuel pump. I never let mine under half a tank. Rarely to 1/4 tank.

I didn't replace the fuel pump this time, just fixed the wiring. I fixed up the syphon side a long time ago but I did check it and all is still good! ;) The syphon comes into play somewhere around 25-30 liters so could leave you stranded before a 1/4 tank. The syphon leaking also can lower your engine running pressure so best to have that sealed up! ;)

Interesting, I didn’t realize the syphon/sender unit could lower fuel pressure….makes sense tho. I should check my pressure now after replacing the sender a few months ago. I put a Delphi pump in several years ago and have been noting about 40 psi at the rail. I think it should be 50?

Yes, I think 50 ish (46 ish stopped) psi is normal but the gauge can be a big factor.
The "pump running" pressure will be higher because the syphon jet creates back pressure on the regulator. Pump "just stopped" will show the pressure regulator setting. The poor wiring connection (sender/holder connector) can be a big problem. I know the fuel pump connector has turned up as a problem on this forum a few times, I just wonder how common it is, and if the Delphi pump connector is a contributing factor ??

Update: Now my "direct wired" pump failed again, and in the driveway again! Haven't got it apart yet but I wouldn't be surprised if the big voltage drop across the old connector was really hard on the pump and now it gave out completely. My son on the extreme end of the Autism spectrum sometimes spends a lot of time in the car with engine idling idling on the driveway so that is why it was in the driveway both times that it quit! ;) Could be that the engine idling with the A/C and headlights on dropped the voltage, increased load/heat and pushed the pump over the edge. A partly plugged fuel filter could be adding to it as well, I changed it once I think around the 250k km but not since with 498K km now.