I recently bought a 94 ranger at a used car lot for 400$ with the plan of teaching my girls to drive standard. It has a L4 mated to a 5 speed all with 60k original miles. At that price few dings and scratches and new fuel pump made it to good to pass up. Recently though if at around 1/4 tank or less a hard stop or hard turn will cause the engine to die like fuel shifted away from pickup screen. But on trying to restart it acts as if out of gas. Tried cycling the key on/off and noticed couldn't hear fuel pump. Went to get voltmeter 10 min walk away. 5 mins later 12 year old daughter drives up behind me said it just started running. I had new delphi on shelf and couple relays so went ahead and installed them with new filter. Still same. Remembered inertia switch and bypassed it still same. When this does happen I've noticed running jump wire at f/p relay does no good. I'm at loss where do I look next?

 

My '94 with 4.0l will do the same when under 1/8 tank on a downhill right hand turn.

It is in the fuel tank pick up, don't bother looking anywhere else.

Just keep tank above 1/4

If you can't hear the fuel pump for 2 seconds each time key is turned on then you have a bad connection or bad pump.

In tank fuel pumps do have a thermal circuit breaker, if pump gets too warm the bi-metal temp sensor separates to cut power to the motor, when it cools it makes contact again.
Motor may be running too warm when tank is low on fuel, and uncovering it when turning or stopping may trip the thermal switch, long shot

 

So the thermal break is in fuel pump itself so that's what makes jumper at relay ineffective?

 

Yes, it is in the fuel pump itself but still a long shot as the problem.

If you have a volt meter hook it up to the inertia switch inside that cab.
With engine running you should see 13.6 to 14.9volts, alternator voltage.
Watch that voltage when engine cuts out, if it drops below 7volts while engine is still running(even stumbling) then power is being cut to fuel pump.

Inertia switch voltage is monitored by the computer, so with key on engine off you will see 5 to 7volts at inertia switch, no amps though so doesn't "run the fuel pump".
When you first turn on the key the computer closes fuel pump relay for 2 seconds to "prime the fuel system", you will see 12-13volts, then you will only see the monitor voltage until engine starts and alternator takes over, 13.6-14.9volts, alternator voltage starts high and then drops to 13.6volts after a few minutes of engine running.

If power is being cut to fuel pump the computer should set a code, that is what the monitor circuit is for.
So if possible have the codes read.