4.3 ZR2 Fuel Pump Replacement ??'s

[mx6rrr]

I wrote this in the non specific area because I know the 4.3 and that fuel pump works on alota diff vehicles....
Just replaced my fuel pump in my '00 S10 ZR2...
There are 3 gas lines running into the pump
Anyone know which one goes where?? And what is the box behind the fuel tank that one of the lines runs to??
Thanks for any help!!

[maxwedge]

One line is fuel delivery. The other is return and the 3rd is tank vent. The "box" is the vapor cannister. The lines are all different sizes so they can only go on the tank fittings one way.

[mx6rrr]

Ok awesome, thank you! I havent had time to go work on her yet...just swapped the radiator in my alltrac...grrr 2 many cars 2 lil time!

[mx6rrr]

Ok I put new connection clips on the hoses and they are all on and seem to be ok, next problem though...when I turn the truck to ingnition, I dont hear the pump running, when I shut the ign off, it sounds like its running!!??! Im going to take the multimeter with me next time and see whats going on but got any ideas??

[jsteale]

I just replaced the fuel pump on my 95 zr2... I not sure what is going on with your pump but i can tell you how it is supposed to work... when you turn the key on the pump should run for about 2-3 seconds and shut off. The fuel pump relay is in the glove box (top back) behind a cover... there are 2 fuel pump circuits. ... one goes through the relay and the other through the oil pressure switch so that even if the relay fails the motor will still run... it will take longer to start as the fuel pump will only run after you crank the engine long enough to get the oil pressure up. If i remember correctly there was only one deuce connector and a ground wire... check the wiring diagram... you should be able to check the relay circuit with a test light... my understanding is that if the oil pressure circuit is out the motor won't run... it's a failsafe... it should be pretty easy to tell if both circuits are working properly.

[old_master]

Originally Posted by jsteale

...The fuel pump relay is in the glove box (top back) behind a cover.

On 2000, the fuel pump relay is in the underhood fuse panel.

Originally Posted by jsteale

....my understanding is that if the oil pressure circuit is out the motor won't run... it's a failsafe....

Not a fail safe measure by any means. The resaon for the redundant circuit is to increase the available current at the fuel pump. If the fuel pump relay or the oil pressure sending unit fails while the engine is running, the fuel pump will still run. Oil pressure dropping to zero while the engine is running, will not shut off the fuel pump. The circuit was only used on certain model year S, T, M & L body GM vehicles. 2000 S & T body is not equipped with the circuit.

On certain older, (1970's and early 1980's) GM models with electric fuel pumps, the fuel pump circuit did go through the oil pressure sender. If oil pressure went below 7psi, the fuel pump would shut off.