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93 bravada - error code 54, fuel pump, fuel relay


mwmoes
06-05-2007, 10:06 PM
I have a 1993 Bravada with 200600 miles. Drove to restaurant and car ran perfect. Ate dinner and came back 90 minutes later and car would not start (spark was there, definitely no fuel). Immediately noticed that fuel pump was not running when I turned the key. I checked for error codes and found 54 (low voltage fuel pump).

I replaced the fuel sending unit and the fuel pump (and fuel tank while I was at it). Still get same problem...

Yup. It hurts. :)

I should have started with replacing the fuel pump relay, but I didn't, so that's where I'm at now. Unfortunately, I can't find it. My book says that it is located in the convenience center underneath the center dash in a bank with a few other relays. I've removed a lot of stuff but I cannot find it. I've searched the internet and can't find any direct location of it. Am I missing something obvious?

I'm also looking for the fuel pump test connector. The forum and my book says that it is under the hinge on the drivers side or on the drivers side wheel well. I can't find it here either. I did find a red wire there and I traced it back to the area on the back firewall behind the engine just to the left (as you face the engine) of the intake manifold. There is a few wires leading to a module mounted on the wall and there is a gray wire that leads off it that has a connector with nothing connected to it. This is my guess, but I don't want to randomly apply 12V so something that I'm not 100% sure!

Any assistance would be most appreciated!

Thanks, Mike

MT-2500
06-06-2007, 09:45 AM
Fuel pump relay is on fire wall left side of brake booster.
Fuel pump prime is a single gray wire that may have a green plastic end.

Check EMC B fuse for power.
That feeds orange wire 12 volts to relay.
Gray wire from relay feeds 12 volts to fuel pump.

When the engine is cranking and oil pressure comes up the oil pressure switch should also turn on fuel pump.

If 12 volt power to relay on orange wire and relay is good.
Then check for 12 volts on gray fuel pump wire on key on prime up or engine cranking.
Let us know.

Scrapper
06-06-2007, 10:24 AM
can you hear he fuel pump now??because a new pump you sould hear it better after you replaced it..another thing could be a coil but you say you have spark so it shouldn't be coil..good luck...

mwmoes
06-06-2007, 04:18 PM
MT-2500's troubleshooting tree was most helpful...

I found the fuel pump relay. It was in a bank of two relays mounted on the firewall in the area behind the power steering reservoir. I was able to indentify it by the orange and gray wires. I'm not sure what the other relay was.

I had a operable fuse at ECMB and 12V. I had 12V on the orange wire coming into the relay. I went back to the fuel pump and unplugged it and found 0V on the gray wire. I checked for continuity on the gray wire between the relay and the harness to plug in the fuel pump and it was functioning.

Note that I did not need to crank the engine to determine these voltage.

I then went to the auto parts store to get the relay. Note they did not have anything under "Fuel Pump Relay" in their system so they did a cross reference on the part number on the old relay. $10.95.

Put in relay. Car started!

Note to readers... Check the $10.95 part (1 hr) before spending the $204.50 on the fuel pump and sending unit (6 hrs).

My electrical weakness was exposed in this repair. Lesson learned. Will spend more time troubleshooting next time.

Thanks for your help!

Mike :)

MT-2500
06-06-2007, 05:02 PM
MT-2500's troubleshooting tree was most helpful...

I found the fuel pump relay. It was in a bank of two relays mounted on the firewall in the area behind the power steering reservoir. I was able to indentify it by the orange and gray wires. I'm not sure what the other relay was.

I had a operable fuse at ECMB and 12V. I had 12V on the orange wire coming into the relay. I went back to the fuel pump and unplugged it and found 0V on the gray wire. I checked for continuity on the gray wire between the relay and the harness to plug in the fuel pump and it was functioning.

Note that I did not need to crank the engine to determine these voltage.

I then went to the auto parts store to get the relay. Note they did not have anything under "Fuel Pump Relay" in their system so they did a cross reference on the part number on the old relay. $10.95.

Put in relay. Car started!

Note to readers... Check the $10.95 part (1 hr) before spending the $204.50 on the fuel pump and sending unit (6 hrs).

My electrical weakness was exposed in this repair. Lesson learned. Will spend more time troubleshooting next time.

Thanks for your help!

Mike :)

You are welcome and thanks for posting back how it went.
Glad you got it going.
And 10-4 on the check it out first.
Even a code does not say replace the part.
Code 54 on yours is the pcm not finding/seeing 12 volts on the fuel pump wire within 2 seconds after key is turned on.
Or no 2 second prime up when key is first turned on.

On yours if the oil pressure switch is working right it should turn on fuel pump after pressure come up. Or a little extra cranking to get oil pressure up.
It may not be working up to par to.
You can check it with engine running pull fuel pump relay and if engine keeps running it is ok.
Good luck
MT

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