my 91 ls 400 died while i was driving it today, i have power and it cranks but wont turn over... what could the prob b... let me kno

 

out of exhaust fluid.
guaranteed.

 

sure sounds like it.......

 

could be a number of things, need more info.

 

More info needed, lots. Did you just run out of gas, is there some in the tank? Did it feel like it was running out of gas or did it just completely die, no warning? It could be the fuel pump, timing belt snapped, or many other things. More info.

 

Well befor it just died in traffic, the car was sitting for 3 weeks because it died then. I though it might have something to do with the injector so I just let it sit for 3 week. Then it just started out the blue... I filled the tank and put that Lucas injection cleaner in, one day later the car don't start... I'm going to get it tested but was just looking 4 some in site... 1 Luv...

 

It might be the fuel pump, pump relay, or pump ECU. The fuel pumps are known to work, and not work, when they feel like it. You can check easy enough if it is getting fuel. To do that you would open the diagnosis box in the engine bay, use a piece of wire or paper clip and connect terminals +B and FP (the 2 front corner terminals), turn ignition on (do not start engine), check the fuel inlet hose to see if there is pressure by squeezing it. You will also hear fuel return noise. Also the little screw on top of the fuel pressure pulsation damper jumps when the 2 terminals are connected. If there's no pressure the things to check are;
Fuses
EFI Main Relay
Fuel Pump ECU
Fuel Pump
ECM
Wire connections

 

A couple years ago mine had power and would crank but wouldn't start, but that was after I had driven it to school one morning and came back to it that afternoon. A busted fuel pump was the culprit.