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2000 Cadillac Deville fuel trouble

I had trouble a couple of weeks ago with this car having intermitent starting problems that seemed to be fuel related and replaced the fuel filter on it. That appeared to have fixed it because it definately was clogged and had reduced fuel flow, we’ve been driving the car ever since then. Today we were getting ready to go out of town and I stopped to fill the tank before we left. I started the car and began to leave the station when it sputtered and died. The tank was not empty, probably 3/8 of a tank before fill-up. I removed the engine cover and used a screwdriver to depress the valve on the fuel rail and while the key was in the run position there was just a slight trikle of fuel from it. Is it the fuel pump thats bad or is there a relay or something similar that could be causing the problem? I checked the fuel pump fuse and it is good. By the way, this car only has 68,000 miles on it.

Fuel pressure regulator?

Is there a way to test it?

You’ll need a fuel pressure test gage and (I recommend) a Haynes repair manual from the parts store. The procedure will be in the Haynes manual and probably in the test gage package also.

Before doing that, let me suggest that you listen underneath by the gas tank while someone turns the key to “on” and see if you hear a muted humming sound. If not, your fuel pump isn’t running. If that’s the case, check to see if with the key “on” you get voltage to the pump. If you do, the pump is shot.

You might be able to check RESIDUAL fuel pressure with the ignition key in RUN; but, it’s not reliable.
The only sure way to check fuel pressure is with a fuel pressure gauge. You may have to get an adapter from the Internet.

Would the pump not pressurize when the key is in the run position? The reason I ask is when I replaced the filter on the car there was no key in the ignition and there still was power to the pump. When I loosened the threaded fuel line at the filter to relieve pressure the pump began to run and re-pressurized the system. I had to disconect the battery to keep it from running. I thought about loosening this connection again just to see if it pumps up again.

OK here is a little update. I turned the key to run position and got under the car and loosened off the threaded fuel line to the filter, no pressure at all. I got my rubber mallet and hit the tank several times, still nothing. I don’t hear a hum from the pump either. So, I checked the pump fuse with a meter, it’s good. I pulled the relay for the fuel pump and checked it with a meter, also appears good (resistance across the coil and closes the circuit when you shut the points). With the key in run position I have 12 volts going into the relay but cannot get a reading comming out of it. Do you have to crank the engine to get voltage through the relay or should it be “hot” with the key on? Is there something on down the line that completes the circuit other than the pump? if I jump across the relay would that be enough to see if the pump will run?

Well, it looks like a fuel pump is probably the problem. I had the wife turn the key to run position while I watched the relay, with it’s cover off, and it closed for about 2 seconds and then opened again so that tells me it is working because I had 12 volts at the other side of the relay for 2 seconds. I still don’t here any pump hum. Unless there is anything else that could interupt the circuit it looks like I’ll be replacing a pump :frowning: One bit of good news about this car is that you don’t need to drop the tank to replace the pump. There is an access plate in the trunk. :slight_smile:

Here is one more question about this car for you guys and maybe all computer controlled cars in general. I have learned here that when you turn the key to the “on” or “run” position it energizes the pump for 2 seconds then stops even though the key is still in the run position. And if you continue to start the car the pump will energize and run as long as the car does. What I don’t get is how does the pump continue to be energized after the car starts when it only stays energized for 2 seconds in the begining? Is it something in the computer that signals the pump to run because the engine is running? I assume that must be the case.

Yes, the engine computer will let the fuel pump run for only two seconds, if the engine isn’t rotating. Yes, there are input signals to the engine computer that tells it when the engine is running.
Once the fuel pump has pumped up to full pressure, why should it run, even for two seconds? If you disconnected the fuel hose (say, at the engine), you could relieve the fuel pressure, and then the fuel pump should run for two seconds at a time.