Stumbling At Startup

[1997ThunderbirdLXV6]

Is it supposed to?

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

: from what I Googled, the Taurus has a returnless system.

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 (?).

 

[XR7-4.6]

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

Who says it doesn’t?

 

[Kenz]

Who says it doesn’t?

View attachment 11334

I left that off when I replaced the pump.

My reasoning was that most aftermarket pump assemblies don't have them.

 

[Grog6]

iirc. turbine fps dont use them, ours might.

 

[Kenz]

Sounds right.... I'm also good to make up to 850hp now

 

[XR7-4.6]

I left that off when I replaced the pump.

My reasoning was that most aftermarket pump assemblies don't have them.

Same here it’s just there for NVH as far as I can tell anyway.

 

[1997ThunderbirdLXV6]

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...

 

[XR7-4.6]

But what do you gain by removing it?!

Nothing perceptible, but like most NVH items I’ve gotten rid of I don’t miss it

 

[Kenz]

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

 

[1997ThunderbirdLXV6]

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.

 

[LukesCougar]

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.

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.

 

[1997ThunderbirdLXV6]

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 .

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.

 

[Kenz]

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.

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