No power to 1993 Buick Century fuel pump

buick
gasoline
pump
relay
century

#1

My 1993 Buick Century stopped running last Saturday, I had to tow it home. Earlier that day, it stalled but after letting it set for about half an hour, it started up and ran normally. Later, it just quit. At home, I found it wasn’t getting any fuel. So, I (of course) pulled the fuel filter and blew out a bunch of goopy fuel. I’ll be replacing that today. But upon further examination of the fuel system, I found that there is no power to the fuel pump now. The pump is fine, I ran a jumper wire from the battery to it and it pumps a good stream out of the fuel line where the new filter will be. I have swapped my relays around to see if it was the relay without any success in getting power to the pump. What else can I look into? All connections seem fine.


#2

There is a fuel pump/oil pressure sender/switch which allows power (12 volts) to go to the fuel pump WHEN there is oil pressure. It, also, tells the engine computer if there is OIL pressure. If this switch isn’t working, OR, IF THE OIL PRESSURE IS TOO LOW, the fuel pump won’t continue to be powered through this switch, and the engine won’t run.

During engine CRANKING, the engine computer (dark green/white wire) should energise the fuel pump relay and allow power to go to the fuel pump via the gray wire FROM the relay.

The wiring diagram is Fig. 72 at this link: http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c152800cc74b Your mechanic could use this wiring diagram, and an electrical multimeter to tests these circuits. I would like to know if ANYONE does any of these checks (just curiosity).


#3

I was working on doing these checks until I couldn’t figure out which relay was for the fuel pump. I’ve been searching all morning trying to find the wiring diagram, thank’s a million. I even searched the autozone website. What search terms did you use to find that? I’ll post the repair once I achieve some success.


#4

Look for the fuel pump relay near the left strut tower. It may be in a black plastic cylinder with a lid. Look carefully at the top of the lid. It should say something about “fuel pump relay”. There is a red wire, with a female terminal, just “hanging around”, near the left strut tower. Follow this red wire to the fuel pump relay.


#5

Joe,
Go down a couple pages in Car Questions and look at " 95 LaSabre Fuel Pump Relay". His finding of a poor ground, may help you.


#6

The wiring diagram did the trick, only one of the relays has the orange-red-black/white-gray-green wires. I found that after removing the relay, I was able to set a jumper and get power to the pump as follows …
Orange to gray - the pump runs constantly, key on or off.
Red to gray - the pump runs while the key is turned on.
Dark green to gray - the pump runs only when the key is in the ‘Start’ position (cranking, as you mentioned earlier).

As for the problem of the pump not running at all, I made a fool of myself once again. After playing with it to see if the pump was ok, I forgot to plug it back into the harness sigh silly me. It works pumps fine now. It even built up a nice back pressure in the clogged fuel filter I stuck back on the line to see if any fuel at all was getting through, … not a drop.

But you did help me figure out which relay is the fuel pump relay on a 1993 Buick Century … the one with orange, red, dark green, gray and black/white wires … and for that I am grateful.

Thanks a million!


#7

I’m glad that you found your problem: plugged fuel filter.
One caution: You shouldn’t connect the dark green/white wire (from the engine computer A11) to the gray (fuel pump power supply wire) the amperage draw could damage the ECM (engine computer). The dark green wire energises the fuel pump relay, NOT the fuel pump.


#8

Ah, thanks again, it was just for a few seconds so I’ll hope for the best. Where would the parts industry be without half-wit shadetree mechanics like me huh? lol sigh Good note for anyone else who reads though. I hope this helps someone else out as well.


#9

Hello,
Looked evrywhere at the site with the link for Fig 72 wiring diagram. can’t find it. Found some stuff but not the wirking diagram. I’m have problem car won’t start, turns over won’t start. Changed fuel filter, check fuel pump seems to work.tried a new fuel pump relay…no dice. I’d really like to find the wiring diagram, check oil pressure sensor.
Regards,
Ed


#10

my wife has a 1994 buick century i got same problem, i changed fuel pump, fuel filter and fuel/oil switch relay and computer bc im not getting the 12v out of the computer. after all that i still got same problem. the ignition modular was also changed. the car will run on starter fluid, the computer pins 1&8 have battery voltage and ground ohm out to be good all wires going to relay also do too.