Stumbling At Startup

Rodeo Joe said:
Is it supposed to?
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No. Let me rephrase my question: why is the Thunderbird not supposed to have a fuel pulse dampener?

Rodeo Joe said:
: from what I Googled, the Taurus has a returnless system.
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For '99? I think that came later, 2000 potentially. Looking at Tascaparts, '99 is the last year that Taurus V6 24V uses the same fuel pressure regulator as Thunderbird V6. I physically verified this on the junkyard Taurus.

Once they go returnless, I think there's no more fuel pressure regulator, but a pressure sensor instead (?).
 
iirc. turbine fps dont use them, ours might.
 
Sounds right.... I'm also good to make up to 850hp now :LOL:
 
Kenz said:
I left that off when I replaced the pump.

My reasoning was that most aftermarket pump assemblies don't have them.
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Same here it’s just there for NVH as far as I can tell anyway.

IMG_2901.jpeg
 
But what do you gain by removing it?!

And side note on NVH: Valvoline Restore & Protect for the last four oil changes has made my engine run as smoothly as butter. I know, it's just oil...but I'm not imagining this!

Meanwhile I'm noticing new suspension noises. There's always something...
 
Less connections on a difficult to access, in take pump is a plus. That pulse damper appeared to be just plastic and had a crimped on metal cap. Removing it eliminates a few possible failure points
 
Weird observation...
Since I got the new battery, the stumbling hasn't happened. To reiterate, the stumbling symptom used to happen fairly consistently when starting an already hot engine on a warm/hot day, with maybe 10-20 minutes downtime between drives.

The other day it was very warm, and I was running errands. Repeated short trips. The exact scenario that would inevitably produce this symptom, which I associate with vaporized fuel as a result of dropping fuel pressure after shut down.

Yet nothing happened. It may just have been a lucky day, plus I don't see how the battery could have any impact on this.
 
1997ThunderbirdLXV6 said:
Weird observation...
Since I got the new battery, the stumbling hasn't happened. To reiterate, the stumbling symptom used to happen fairly consistently when starting an already hot engine on a warm/hot day, with maybe 10-20 minutes downtime between drives.

The other day it was very warm, and I was running errands. Repeated short trips. The exact scenario that would inevitably produce this symptom, which I associate with vaporized fuel as a result of dropping fuel pressure after shut down.

Yet nothing happened. It may just have been a lucky day, plus I don't see how the battery could have any impact on this.
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Maybe a loose connection, or pcm was being funky and swapping the battery did a partial reset. Loose battery cables or a weak battery can cause a stumble/ miss from my experience.

While battery issues could cause a stumble idk what relation it would have to the noise you were hearing. Also when i had a weak battery it would miss if i got on it good. Not just at stops and starts.

Edit: id also mention idk jack about the v6s. Ive had similar issues with the v8 though.
 
LukesCougar said:
While battery issues could cause a stumble idk what relation it would have to the noise you were hearing. Also when i had a weak battery it would miss if i .
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The only explanation I can come up with is this:
Assuming the noise and stumble come from vaporized fuel, and re-liquefying that fuel requires pressure, maybe the fuel pump didn't get full voltage with the old battery, causing a delay in building pressure. With the new battery, it builds pressure instantly, ergo problem solved.

This is me hypothesizing without any specific knowledge about auto electrics.
 
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1997ThunderbirdLXV6 said:
The only explanation I can come up with is this:
Assuming the noise and stumble come from vaporized fuel, and re-liquefying that fuel requires pressure, maybe the fuel pump didn't get full voltage with the old battery, causing a delay is building pressure. With the new battery, it builds pressure instantly, ergo problem solved.

This is me hypothesizing without any specific knowledge about auto electrics.
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Sometimes my Cougar is parked and not driven a few weeks at a time. After that amount of time the battery is down a bit on charge and it cranks slower.
Before I replaced the fuel pump, the old pump made a noticeably different sound when the battery was low and the car took longer to start. With the new pump it has now it seems to make no difference.

Guess what I am getting at; the lower voltage seemed to make a difference on the original pump. The aftermarket modern unit seems to not be affected.

So you could very well be right
 
So this issue is back, and now I have video proof. Or rather just audio.

What you're hearing in this very brief clip is: I turn the key to ignition on; the fuel pump primes; simultaneously, a whooshing sound comes from the right side of the car, presumably from the fuel lines.


Since this is an old thread, below I'm pasting my initial post from page 1 for your convenience:

"Hello All,

This isn't a new problem, but one that occurred today for the first time in a while, potentially because it was the first warmer day in a while.

After much reading, I have an idea what might be going on, but I wanted to pass it by you all.

Situation:
  • I'm running several shorter errands around town; engine is warm; time between drives is anywhere between 10 to 20 minutes.
  • Tank is almost full; 30 miles since last fill-up.
  • At startup of the warm engine, I get significant stumbling/sputtering accompanied by a slight whooshing sound for about 15 seconds (best guess), which can be shortened by revving the engine a bit; then the idle gradually normalizes.
  • Today I actually turned the engine back off, and then I cycled the ignition a few times; each time the fuel pump primed, I could hear the same whooshing sound.
  • When driving off, everything turns back to normal, except during the first few seconds of initial acceleration, when I'm hearing a sound akin to tiny rocks traveling through a pipe; that sounds comes from the right side and seems to travel backwards (as if through the fuel return line?).

All this leads me to the conclusion that there's some sort of fuel vapor condition. There are no visible leaks anywhere in the engine compartment nor under the car, nor any fuel smells that I can tell.

Any thoughts or advice what I can do to alleviate this?"
 
Where was the microphone for that recording? The fuel lines wouldn't make that kind of noise, that sounds more like air rushing over the microphone.
 
theterminator93 said:
Where was the microphone for that recording? The fuel lines wouldn't make that kind of noise, that sounds more like air rushing over the microphone.
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It was in the phone holder on the center console. But the fan was off and doors and windows closed. There was no air rushing. But yes, that is what it sounds like.
 
It sounds like the fuel is cavitating or being turbulent when it is spit back into the tank
 
theterminator93 said:
Got a buddy who'd be willing to listen around from outside the car while you manipulate the key (or vise versa)?
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I mean I could just put the phone on the ground recording while I cycle the ignition. Next time I restart it when it's hot. But I'm convinced it comes from the fuel lines (though I don't know if it's to the engine, return, or vapor line).
 
Ok...hot car, came home, unpacked shopping, roommate got into the driver seat, I got on the ground on the passenger side of the car, he cycled the ignition, and I said "do it again"...repeatedly.

And the whooshing comes from the tank. It's a noise distinct from the pump sound itself, and it always continues for another 1-2 seconds after the pump is done priming.

And hearing it from there, I'm not sure if whooshing is a good description; it's more as though a paddle boat was steaming through my fuel tank... As if the fuel is slushed around.

What next?
 
When the pump on my 96 died, the symptom was intermittent starting difficulty until one day it just ... stopped. Drop the tank, pull the pump assembly and examine/rebuild it? 🤔
 
theterminator93 said:
Drop the tank, pull the pump assembly and examine/rebuild it? 🤔
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I don't wanna...

But yeah, ultimately that's probably inevitable. My best guess is that the root cause of all this is a bad check valve in the pump.

I don't think the pressure regulator is the issue because there are no drivability issues, and there's no fuel coming out of the vacuum hose when cycling the ignition.

I still never actually read fuel pressure because the loaner testers never worked on my Schrader valve.

I'll keep monitoring...
 
1997ThunderbirdLXV6 said:
Ok...hot car, came home, unpacked shopping, roommate got into the driver seat, I got on the ground on the passenger side of the car, he cycled the ignition, and I said "do it again"...repeatedly.

And the whooshing comes from the tank. It's a noise distinct from the pump sound itself, and it always continues for another 1-2 seconds after the pump is done priming.

And hearing it from there, I'm not sure if whooshing is a good description; it's more as though a paddle boat was steaming through my fuel tank... As if the fuel is slushed around.

What next?
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How much fuel was in the tank while you were listening for the noise?
 
If the tank is full enough, that could be gas moving thru the tube over the ds.
 
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