90 cabby named 'lil girl' working on for a friend. I've been thru most of the car fixing everything I can. Was planning on delivery to my friend, but during a test drive a new problem has happened.

I'll be happily tooling down the road. Out of nowhere the rpm drops to zero, the engine shuts off.

Attempts to restart it just result in cranking but no joy. After about 4 or 5 minutes sitting(or i get lucky with swapping relays), it will restart like nothing happened. I can get a few more miles down the road before it happens again.

I've been swapping out various relays, fuel pump, digi, and load reduction trying to find if its electrical related, which I feel it is.

Is it safe to bypass the digi control relay, the fuel pump relay, and/or load reduction relay in order to rule them out as a source of the problem? I suspect that it may be the electrical end of the key switch. I have another electrical end in a parts car I can test with.

I'm thinking about installing my fuel pressure gauge on the car so when it dies I can see if it has any fuel pressure at that point.

Any other ideas?