Fuel pump 96 Chevy

[strik9]

At the shop we simply changed out all the connectors with fresh ones to eliminate the chronic problems.  From the tank to the chassis usually.  Not suprising that all were 90's GM products either.    Had some wonky after market pumps but mostly it was goofy wire connections.

[Heiny57]

I vote for bad grounds somewhere.

[john k]

Fixed it!  Bought a new gas tank,  the current tank seeps a bit when over half full and parked.  Pulled the pump out first.   Looked things over real careful.  Unplugged the pump wiring on the fuel side of the locking plate.  This looked good when i inspected it in the past.  This time the pump ground wire pin was black.  Inside the tiny 4 prong plug was heat discolored at the ground wire.  Cut it off both sides,  soldered in a new wire,  double insulated   the connections with heat shrink tubing.   Ran the wire through a new hole in the plate, and sealed it with black pvc.    I believe this bad dream is fixed now. 

[DeadNutz]

Great news John. I hate those intermittent problems as they will drive you nuts.

[bonneyman]

I've taken to making sure all the accessories are turned off, and then turn the key to the "on" position while listening for the pump. It hums for about 3-4 seconds then stops, and I know the pressure is up to normal. Then I crank it. Plus I carry an extra fuel pump relay to swap out under the hood just to make sure it isn't that.

[Matt_T]

I've taken to making sure all the accessories are turned off, and then turn the key to the "on" position while listening for the pump. It hums for about 3-4 seconds then stops, and I know the pressure is up to normal.

KOEO the pump is usually shut off by a timer not a pressure switch. It's a good test to confirm the pump is running but doesn't normally tell you anything about fuel pressure.

[J.A.F.E.]

Interesting I also thought the pump shut off at pressure.

[Matt_T]

Interesting I also thought the pump shut off at pressure.

Generally no, there haven't even been any fuel pressure feedback switches or sensors until fairly recently. Fuel pressure was controlled by a regulator on the rail, which dumped fuel back to the tank via a return line, whilst the pump ran continuously.

IIRC early fuel injection systems didn't shut the fuel pump off when the engine wasn't running which caused some wrecks to turn into infernos. So timers were introduced which only allowed the fuel pump to run a few seconds without the engine running. This is usually built into the ECM/PCM rather than a physical timer relay.

[J.A.F.E.]

Makes perfect sense. I was aware of the return lines and the pressure sensor would be added cost to the system - the timer is just some lines of code.

Thank you. 

[john k]

 Used to listen for the pump noise.  But my hearing loss, and any traffic or wind noise put a stop to that.  Funny how hearing loss slips away.  One of those early pumps delivered enough pressure to spray the underside of the hood, but the truck was a no start.  When i bought a fuel pressure gauge, found that punp was putting out 15 psi, spec calls for 50 -65 psi. Of course by that time the reciept had vanished.  Right now truck is running great for its 211,000 miles.  Just made a 150 mile trip pulling a car trailer.