javadog

2003 S8, 109k miles. no running problems, ever. Left the car outside for 2 nights, temps down to 20-30 degrees at night. Started it early one morning and ran it 20 seconds to move it into the garage. Didn't drive the car for a couple days after that. Next time I got in it, it cranked a little slow, tried to start and died. Might have fired on on cylinder, might have made a muffled popping noise. Repeated cranking attempts failed to start it. Checked the battery voltage, was 12.19. Charged battery fully. Car would crank normally but not start. Read about having to turn the key to position 1 and hold it for 5 seconds before starting if a battery has been replaced, so I thought maybe the battery voltage had dropped low enough during the initial failed start to trigger this. Went through this procedure and the next time the engine cranked, it sounded like it was trying to fire on one cylinder. To make sure I was getting good spark, I dribbled a little starting fluid into the front of the air cleaner assembly and the next time I cranked it, it stated to act like it wanted to start. Cranked it two more times and it got better each time and it finally started. Ran rough initially, idle was low, but got progressively better and finally cleared up. (Made a fair amount of lifter noise at first but that went away.)

It seemed like it was running normally and would accept throttle, but it died again after 45 seconds. Have since started it 3 or 4 more times, it runs normally at first, then hesitates more and more when giving it throttle, until the idle drops and it dies. Seems to die every time at about the 45 second mark. The impression I get is like the fuel pressure is slowly dropping. Doesn't turn on the check engine light.

Don't have a code reader, fuel pressure gauge, or anything useful to diagnose it with. I am getting ready to move in a month or two and planned to do a full service on the car when I get to where I'm going, really don't want to get into that now.

Any ideas, other than throwing random parts at it?

jfrahm

Has the fuel pump ever been changed?
Try shooting starting fluid into a vacuum line (like the handy EGR lines) and if that keeps it running it's probably the fuel pump, particularly if it's never been changed.

javadog

The fuel pump has never been changed. I think it is definitely a problem with fuel, but It's hard to say if the pressure is dropping or the pump can't deliver the volume. The pressure could be other things, like a failing pressure regulator. The odd thing is that the demand for fuel is greater at a cold start than later in the warm-up cycle and it starts normally now, after a couple revolutionss. So, the pump is easily building pressure from zero when off, to 3 or 4 bars when running. Also, I would think that failing fuel pressure would turn on the check engine light, which isn't happening.

I also have a hard time with coincidences and that makes me wonder what about the initial problem could now cause this? I'm trying to think it through logically.

For what its worth, it should have about 4 gallons in the tank.

jfrahm

When dying the pump often runs and then sticks, unsticks, runs again for a bit, etc. You might get multiple lean codes but you might not, when one of mine was dying I did not get codes.

javadog

Okay, did a little more tinkering and made some progress. I think the pump itself is fine. It runs fairly quietly. I had wondered if the dying after 45 seconds was caused by the fuel pump draining the fuel completely out of the cup that it sits in. To test this, I started the car and let it run, then when it started to stumble, I dumped about a gallon of fuel through the filler, which should dump fuel down into the cup. As I did so, the engine began running normally again. I continued to let it run for 3 or 4 minutes, long enough to drain the fuel back out of the cup if it were not getting refilled and it ran fine. So, I know that the fuel starvation was caused by draining the fuel out of the cup that the pump sits in and fuel is being now syphoned out of the sides of the tank now and back into the cup, because the engine now runs longer than it would take to drain the cup if it were not being refilled.

I'm tempted to think that my problem is fixed. What remains is to figure out why fuel wasn't refilling the cup until now and how the cup "lost its prime."

audinutt

don't kid yourself, your fuelpump is in the early stages on failure. I've had the same exact symptom prior to complete failure

javadog

Ran the car some more over the weekend and had no more problems, drove it today and it drives fine. I think I've just about figured out the sequence of events that led from the initial no-start from low battery voltage to the issues with the fuel pump losing its prime. I don't think I'll have any more issues with it for now, the pump seems pretty quiet, but I may start a new thread to ask about a few things related to the electrical supply and the main computer, so to confirm what I think happened.

Bottom line, don't attempt to start one of these with a fairly discharged battery and, if you do, make sure you reset the computer gods after charging the battery by turning the key to position 1 for at least 5 seconds before engaging the starter. My repeated starting attempts that I did before I remembered about the reset were what did me in.

Thanks for the help.

audinutt

I predict you will be looking for a fuel pump procedure in the next 500-1000 miles... Just speaking from experience.
Replacement is cheaper than a tow. If you DIY

BrianC72gt

Yup. The pump doesn't have to work as hard when the cup is submerged, over half a tank or so. Lower than that it is trying to vacuum lift fuel to the cup using one port, then pump the fuel through the lines using the other. A dying pump can still do the former when it gets iffy about doing the latter.

javadog

Such gloom and doom...

It's been two and a half years, so I thought I'd update the thread. The car still runs fine, no issues. Pump is just fine. The issue that I had was described in my last two posts and the solution was simply to dump a little fuel into the tank, so the pump could recover it's prime and the system had enough time to get to where it kept the cup around the pump full of fuel. It takes a little bit of running to achieve that, once the level has gotten below a certain point.