Does 2000 Mercury Mountaneer have a Factory Fuel Return Line

[federicoastiz]

I have a 2000 Mercury Mountaneer (same as Ford Explorer) with a vapor-lock issue and would like to know if this model has an existing Factory Return gasline.

 

[Mbrooks420]

No. Returnless after mid 98. Why do you think it’s vapor locking?

 

[J_C]

I second that, no it does not have a return fuel line. Most fuel problem troubleshooting begins with checking the fuel rail pressure.

 

[federicoastiz]

No. Returnless after mid 98. Why do you think it’s vapor locking?

Stall and/or hesitates when temps are usually in triple digits here in Tucson Arizona. After letting it cool down, depending on time of day, it will start up....has all the symptoms. Was thinking about installing a vapor separator fuel filter, but don't want to be putting holes in the tank for a return line.

 

[Mbrooks420]

I’d bet it’s the fuel pump starting to fail.

 

[Turdle]

^^^
engine coolant temp sensor would be second guess. Classic symptom.

There are 2 coolant sensors. One is a sender for the gauge, and has one wire in it's connector. --ignore this one.

The actual sensor "talks" to the PCM and controls fuel trims based on engine temperature, usually has 2 wires. It's located in the crossover pipe fitting.

 

[federicoastiz]

^^^
engine coolant temp sensor would be second guess. Classic symptom.

There are 2 coolant sensors. One is a sender for the gauge, and has one wire in it's connector. --ignore this one.

The actual sensor "talks" to the PCM and controls fuel trims based on engine temperature, usually has 2 wires. It's located in the crossover pipe fitting.

I will take a look, thanks.

 

[J_C]

Wouldn't vapor lock do screwy things to the fuel pressure, perhaps initially higher but tapering off faster? It seems like a fuel pressure reading would be useful as well as a scan tool capable of live data so you can look at fuel trims and the temp sensor reported value, among other things.

 

[J_C]

Stall and/or hesitates when temps are usually in triple digits here in Tucson Arizona. After letting it cool down, depending on time of day, it will start up....has all the symptoms. Was thinking about installing a vapor separator fuel filter, but don't want to be putting holes in the tank for a return line.

You could just pull the sending unit, put a hole in its tank mounting plate, and weld a pipe onto it, or pay someone off craigslist $10 to weld if you can't. There might also be the possibility of using a '98 or older 2nd gen sending unit with the return line pipe already on it but then swapping in a '99+ pump and pressure regulator onto the sending assembly since '99+ operate at a much higher pressure, though the electrical connectors might not match and need swapped. I could be wrong, never heard of anyone doing this.

 

[donalds]

Fuel pump
Test it when its acting up

I made a full thread about this Awhile back

 

[federicoastiz]

I’d bet it’s the fuel pump starting to fail.

well, it happens every year when Tucson temperatures get above 105 or so...then, as the weather cools down the issue disappears, so I don't think it's the fuel pump, as we replaced it the first time it started to happen but did not resolve the issue.

 

[C420sailor]

Doubt it is fuel temperature related. Your returnless system actually imparts no heat to the fuel in the tank, unlike a return system, keeping fuel tank temperatures cooler than in earlier models. A return system slowly heats the fuel in the tank as excess pressure from the hot rail is returned to the tank.

That, and the fuel in the tank is only subject to convection from the ambient air. There is no direct conduction or radiation. Even on a hot day, your fuel will stay relatively cool.

Really the only possible location you could be experiencing vapor lock would be in the engine compartment, and fuel rail pressure is in excess of 60psi, which decreases fuel volatility. If you told me it was hard to start after shutting down, after heat soaking the stagnant fuel in the feed line, vapor lock would be more likely. If it is running, then starts to stall/run rough, it isn’t vapor lock.

There are members here who drive their Explorers in much hotter climates (Kuwait, off the top of my head). My truck even spent some time in some HOT parts of Texas, with a return system, nonetheless.

Recommend you check fuel pressure, as well as your ignition system. I’ve seen cracked coils get wonky when hot.

 

[Mbrooks420]

I see triple digits every summer and have zero runability issues. I’d check/change the coolant temperature sensor that feeds the ECU as mentioned above. It’s possible it’s reading way colder than it actually is.

 

[reallyfatbastard]

I have a 2000 Mercury Mountaneer (same as Ford Explorer) with a vapor-lock issue and would like to know if this model has an existing Factory Return gasline.

Yes. If you have a vapor lock problem it must have been modified from stock. This engine comes with fuel injection which eliminated vapor lock.
Why do you think it has vapor lock?

 

[RWAG]

Experienced this with another vehicle. Check fuel filter(s) and tank sock. Partially clogged/restricted flow and hot weather will cause fuel vapor lock. In my case was still a problem until I found an in-line filter a previous owner had installed was restricted.

 

[federicoastiz]

Yes. If you have a vapor lock problem it must have been modified from stock. This engine comes with fuel injection which eliminated vapor lock.
Why do you think it has vapor lock?

Like I mentioned above, this is the 4th year that it happens. It only happens when the temperature is usually 105 or above, the rest of the year it runs like a champ. when it shuts down, it won't start up again until it has cooled down.

 

[Mbrooks420]

That’s classic coolant temperature sensor failure.

 

[federicoastiz]

That’s classic coolant temperature sensor failure.

wouldn't that mean, that if the temperature sensor failed, it would have the same symptoms all year round at different ambient temperatures?

 

[Mbrooks420]

It’d get worse as the temperature went up as you’d get farther and farther for your fuel trims.

 

[Mbrooks420]

Next time you fill up and it’s super hot dump a 1/2 cup of marvel mystery oil into your gas. If your actually vapor locking, which I highly doubt, this will band aid it.