I had something very similar with my own - 1986 3.5EFi - which turned out to be the live feed wire.
Old pump had failed - lots of noise before it died.
Fitted the new & nothing.
Bit of head scratching & out with the digital multimeter.
Almost battery voltage showing at the connector in the wheelarch but still no run.
Traced all the way back to the fuse & still OK voltage.
New pump ran fine when connected to a separate battery & the car started. (Didn't manage to blow myself up
)
Decided to check the live at the connector in the wheelarch with a 12 volt bulb.
Nothing, not even a glimmer.
Checked along the wire using a pin to pierce the insulation until the bulb lit.
Which was about an inch up from the connector.
Turned out that 30+ years of exposure to the elements had caused the wire to corrode away to just a couple of strands inside the insulation, enough for a digital MM to show the expected reading but not enough to pass the current required.
ETA I did have fun with a previous pump (might have been the one that failed) after fitting a new tank some years ago - old one had corroded through at the seam.
All fitted & fine until I ran the fuel down to where I would have expected the low warning light to come on.
The low warning light did indeed come on & very shortly afterwards the car slowly came to a stop - fortunately not on a busy road.
Puzzled as I knew I could get at least 30 miles after the light came on with the old tank & putting a gallon in had restored normal service.
Pulled the pump & measured the depth of the tank from the hole. Slightly deeper than the old one.
Examination of the pump showed that there was some adjustment & that solved the issue.
I spoke to the supplier & we measured the other tanks he'd got in stock. No two were identical!
Last night I borrowed another new one from a mate and got the same results ! Refitted the old one and it runs perfect... I've a feeling things are going to get messy unless I can find a decent S/H one 
