Is my fuel pump failing?

mfaerber · #1 08-17-2010, 06:35 PM

Thank you in advance for reading this!

1998 Taurus SE Wagon... (V6 3L DOHC)

Yesterday, after driving the wagon for about 20 minutes in the hot city, the engine began to stutter. The driver immediately pulled over and by the time she got into the grass, the engine stopped. Just before this happened the engine was running too hot (not in the red though) - this is probably due to another problem it has been having where it frequently purges coolant when parked. I have since added more and replaced the cap which looked damaged on the inside (the overflow tank is new). Once pulled over, we could not start the car again, the engine would not turn over, but would try... violently.

After a good bit of googling, it fits the description of a failing fuel pump. I bought a fuel pressure gauge and followed the directions. With the key in the ON position, just before engine start, the gauge displayed a constant 15psi (I tried this twice). I turned the key to crank the engine (and it did after a couple spurts). At this point, the gauge displayed 30psi and stayed at 30 for a couple minutes.

The fuel pressure regulator is new. The spark plugs are a year or two old. I have a nice scan tool, but it is not detecting any error codes or pending error codes. I admit that I frequently allow the fuel level to go well below a quarter of a tank, which I now know is not good for the pump...

What do you all think?

Thanks!

shorod · #2 08-17-2010, 08:34 PM

Low fuel pressure from a weak fuel pump should not cause the engine to struggle to turn over when attempting to start it. That would suggest either the battery is low, the oil is REALLY thick, or there is fluid in the cylinders. Based on the issues with the cooling system that you describe, I'd be inclined to think you might have a problem with the head gasket, heads, or block.

-Rod

mfaerber · #3 08-17-2010, 08:58 PM

The battery is a good one and less than a year old.

I do have a slow oil leak from... somewhere... so I have to add oil every month or so.

I looked up blown head gaskets and I don't have any of the symptoms of a bad one...

mfaerber · #4 08-18-2010, 10:55 AM

More testing:

If there is no pressure in the lines to begin with, and I turn the key to ON/EngineOFF, then the PSI will only ever (slowly) climb to 15psi. Only after repeated turns from OFF/OFF to ON/EngineOFF does the pressure slowly climb to 30-35psi. In either case, the pressure holds once the car is off.

When I crank the engine (there is still a tiny bit of stuttering before starting) the PSI holds at 30-35. When I put the pedal to the floor, by the time the RPMs climb to 3.5, the engine begins to stutter and I'm afraid to push it any further.

When the car left me stranded yesterday, the RPMs were probably around 2.5-3.

mfaerber · #5 08-18-2010, 12:18 PM

FYI: My oil pressure switch (pretty sure that's what it is) is dripping oil through the body of the component - not the threads.

mfaerber · #6 08-18-2010, 03:00 PM

I replaced the fuel filter (was dented/rusted/old looking). Now I'm going to replace the oil pressure sender while I have the car jacked up.

After replacing the fuel filter I used the fuel pressure tester and the results were different from before. Now there is around 20psi even when the car is completely OFF. I stood there holding down the tester's pressure relief valve - and watched fuel siphon into a gas can - for a while and each time the PSI continued to stay around 20psi afterwards. Also different is that the tester's needle moves much faster when I turn the car and crank the engine. I THINK the engine might be cranking better than before.

thoughts?

mfaerber · #7 08-18-2010, 06:08 PM

I replaced the oil pressure sender - looks like that stopped the leak.

65comet · #8 08-19-2010, 01:36 PM

If you do discover that the fuel pump is bad, search my posts and you'll find instructions on changing it. Part of the posts for that thread are on how I figured out it was the pump and not the fuel shut-off switch.

mfaerber · #9 08-19-2010, 02:53 PM

Thanks 65, I'll do that.

So far, the car is driving really well. I plan on holding onto the pump until the day before I'd have to return it in order to get a refund - just in case I need it.

However, I'd really like anyone experienced to either put me at ease, or burst my bubble about what I've done so far and what I can expect later.

Willyum · #10 08-20-2010, 01:30 PM

It sounds like you are confusing the terms "cranking", "turning over", and actually starting. I bought a Carter F.P. last winter and good installation instructions came in the box.

shorod · #11 08-20-2010, 02:06 PM

There is a rev limiter in the car to prevent over-revving the engine when in Park and Neutral. That's why the engine seemed to misfire when you revved the engine during you checks above.

-Rod

mfaerber · #12 08-20-2010, 02:38 PM

Willyum, you are correct - starting the engine is what I mean.

Shorod, that makes sense, I kind of suspected something like that might be going on.

I've driven the car maybe 40 miles since I changed the filter, and so far, everything is great. When there isn't anyone around, I've been driving it hard in order to stress it into giving up any clues that something else is still wrong.

shorod · #13 08-21-2010, 09:27 AM

Do you no longer have issues with the car getting hot and purging cookant followed by hard starts? I don't understand how a fuel filter would fix that.

-Rod

mfaerber · #14 08-21-2010, 01:42 PM

It's too early to say about the coolant.

I just replaced the cap on the overflow tank - I think that was the problem because the old cap was melted/damaged on the inside. But I'm not positive yet, if that doesn't fix it, I'm going to start a new thread for it.

In the past year I have replaced the overflow tank (it did not come with a new cap) and I've replaced the coolant lines going to and out of it.

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