Engine/Fuel problem

Ok guys this question is for a friend of mine in a local Ford club (we all own a bunch of old Ford pickups). I gave him a 94 Blazer with a 4.3 in it that I didn't have a title to and he traded it for a 76 F150 4x4. He can't figure this problem out and I told him that this is the best place I know to go to to get answers to my problems. Here was his post in a S10 forum that got no replies...

I have a 94 S10 Blazer with the 4.3 and it's driving me insane.

I'll be driving down the road and the fuel pump will suddenly quit, leaving me stranded. I'll then have to just sit there for about 6 minutes, turning the key on and off until it decides it wants to prime again, then she'll fire right up.

I thought the new fuel pump I fitted was bad, so I replaced it again yesterday- same problems. The fuel pump relay is also brand new. I haven't changed the fuel filter yet as I can't get the damn thing off - 3 of us have tried so far.

It's going in tomorrow for a custom exhaust, so am going to get them to put the new filter on while they are at it.

When it's sitting there dead in the water, I can turn the key & feel the fuel pump relay engage to prime - but the fuel pump does not run. As I said, it makes me wait approx 5-6 minutes before it will actually prime and restart. I checked the ground yesterday, and the cable was nice & shiny.

Does anyone have any ideas I can try? Is there something I am overlooking?

Any chance this truck has a collision cut-off switch installed in series with the fuel pump's +12V supply? A friends Lincoln did the same thing until the switch was replaced.

Cheers, Mark

Not sure I will ask him. He did say it's losing voltage somewhere between the fuel pump and the relay (I think relay he said).

Oh and no it doesn't have an inertia switch. I just asked and that was his response.