Tons of reading pays off

[TxBugMan]

Thanks to all the post on this site and days of reading i finally figured out my problem. I have a 92 X sport 4X4 with 204k on it. It all started 2 weeks ago after i got my X back from a trans overhaul. I checked my mileage on the second tank and found out i was getting 11.1 mpg when before i was getting high 14 to low 15 mpg. and 2 days later my CEL came on. Thats when i showed up here and started reading. I learned how to check codes and what not to do. I had a P0173 code and figured it was my o2 sensor. I did NOT just go out and buy one but began checking and more reading. to make a long story short I think the fuel regulator is located on the passenger side front of the engine with a braided line attached to it and the vacuum line was disconnected. What was strange was that the nipple where it goes was not clean and shinny like i thought it should be and am not sure how long it was off. Now I'm code free and it didn't cost me a penny thanks to the wonderful people on this site that take the time to share their knowledge and experience.

THANK YOU

 

[Tony H]

The best kind of repair.. FREE

I just did a Window Motor rebuild that I could have fumbled through, But after reading the several How-To's on this site, it was a no-brainer

 

[datbaddwagon]

after reading your post txbugman i found that i had the same problem that i just found it just hanging there thanks for the insight

 

[Tony H]

With that line disconnected it will cause a slight Vacuum leak. The sole purpose of that line is in the event your Fuel Pressure Regulator fails... Diaphragm inside goes bad, it will run gas into that line and into the intake manifold. You will get a rich running condition but the gas wont be spewing all over the engine.

 

[huntman58]

With that line disconnected it will cause a slight Vacuum leak. The sole purpose of that line is in the event your Fuel Pressure Regulator fails... Diaphragm inside goes bad, it will run gas into that line and into the intake manifold. You will get a rich running condition but the gas wont be spewing all over the engine.

I thought the reason that line was there was to raise and lower the fuel pressure as the motors needs changed. I do know with out that line the FPR will let to much pressure get to the injectors and you will run rich but with it when the need is there for a richer supply = higher pressure charge because of low vac it can adjust for that need and that it is not as a safety stop gap to keep fuel from spilling.

Do not mean to start any thing just set it right so some one dose not thinks they can run with out that line or that they can block off the FPR as we on the 1st gens use a return system unlike some of the newer ones out there that do not and use a retunless system

 

[Tony H]

I thought the reason that line was there was to raise and lower the fuel pressure as the motors needs changed. I do know with out that line the FPR will let to much pressure get to the injectors and you will run rich but with it when the need is there for a richer supply = higher pressure charge because of low vac it can adjust for that need and that it is not as a safety stop gap to keep fuel from spilling.

Do not mean to start any thing just set it right so some one dose not thinks they can run with out that line or that they can block off the FPR as we on the 1st gens use a return system unlike some of the newer ones out there that do not and use a retunless system

Fuel pressure is constant. More then enough for Idle up to WOT.
That's why there is a return line in the Fuel system.

 

[2000StreetRod]

You're both right

Prior to 1999 Ford implemented a return fuel system with a vacuum controlled fuel pressure regulator mounted on the fuel rail. Fuel pressure is maximum with no vacuum, less at WOT (when there is little vacuum) and least at idle (when vacuum is most). The PCM is programmed to control the fuel injector pulse width assuming the vacuum line is connected. When the vacuum line is disconnected fuel pressure will be maximim and engine will run rich.

In 1999 Ford switched to a returnless fuel system with a fuel pressure regulator mounted in the fuel tank and a fuel pressure damper mounted on the fuel rail. The damper has a vacuum connection. The PCM is programmed to assume a constant fuel pressure and varies the fuel injector pulse width accordingly.

If the diaphragm in either the fuel pressure regulator or the fuel pressure damper should leak the fuel will be sucked into the intake manifold.

 

[huntman58]

Streetrod that’s what I also thought and being the OP has a 92 that was the info I went on .I also have a 93 and it to uses the return FPR.

This is were not having some specifics can get others into trouble as there are changes threw out the years just as you explained in a way I kind of tried to only I did not know the years were it changed over . Now if a return line FPR person say on a 1st gen ran with no line as you said they will run rich believe me I know and some one with a later Ex will not. now on a 1st gen leaving that line off and running full 40 PSI or more pressure for any length of time a person could not only flood a motor but they could also be spilling raw gas in to the oil pan and washing away the oil from the pistons and rings. So thanks for explaining it so much better then I was as that little mix up could lead to a danger’s set up in some ex's

 

[huntman58]

If the diaphragm in either the fuel pressure regulator or the fuel pressure damper should leak the fuel will be sucked into the intake manifold.

On this one thing only the Vacume line is not there as a safety item but it is there as a control. the sucking fuel into the intake just happens to be a deal that happens because of a malfunction of a part break down the same as a Auto trany shift modulator will make a motor burn oil ( ATF ) if it's diaphragm leaks allowing the oil to get into the intake system.

 

[Deleted member 128963]

Vacuum Line on 1st Gen Fuel Pressure Regulator

This one needs to be a Sticky.

I read this thread just a few minutes ago and just had to grab my flashlight and head outside to look at mine as I have had a sneaking suspicion that I have a vacuum leak somewhere and my in town mileage is also down around 11.5. My vacuum line was still attached, but just barely. When I reached for it, it fell of the fitting. Leaking? Maybe a little, maybe not, but good information. Thanks to all for this.
Bill

 

[casperthealien]

Thank you

wow you know i just read this forum and post and ran out and looked and here the line is off on the system put it on and the engine sounds different right away

 

[Bwana Bob]

Fuel Pressure:

Key on, engine off: 35 to 45 psi
At idle, vacuum hose connected: 30 to 35 psi
At idle, vacuum hose disconnected: 35 to 45 psi


Bob

 

[highwaystar]

photo of vacuum connection needed

can anyone post a photo of where to check this?

 

[Roadrunner777]

I'll be down in that area doing spark plugs in the morning, I'll get a shot of it.

 

[cklinejr]

Would love a photo of this little trouble maker.

-Charles

 

[Maniak]

Would love a photo of this little trouble maker.

-Charles

Post #4 in this thread shows you where it is.
http://www.explorerforum.com/forums/showthread.php?t=187198

~Mark

 

[jjon90]

Would love a photo of this little trouble maker.

-Charles

 

[Roadrunner777]

If you do some off-forum searching, the purpose of the vacuum line is out there, I'm going to try to explain it...

Let's see... the first thing to understand is the spray pattern of the injector, which is optimized for a certain pressure. Think of a nozzle on a garden hose, there is a certain sweet spot. Let's call that differential pressure... the difference between one side and the other.

Ok, step 2: The garden hose is just water pressure on one side and plain atmospheric pressure on the other. Simple. But, for a fuel injector, you have fuel rail pressure on one side, and intake manifold vacuum on the other.

Now, the real meat of the problem: intake vacuum, negative pressure, if you will, changes with throttle plate position, lots of stuff. We can't change that, it's how engines work. So, how do we maintain that optimum spray pattern?

The answer is we change fuel pressure based on intake vacuum. That way, the optimum differential pressure across the injector, and the optimum spray pattern are maintained. And we do that by running a vacuum line to the backside of the regulator.

Oh, that roadrunner ****eth on us, no.... you can test this for yourself. Just hook up a fuel pressure gauge. And, boy, if you have a 1st generation ex, you need a fuel pressure gauge, so buy one.

With the gauge attached, run the engine and goose the throttle. Watch the fuel pressure go up when the throttle plates are open. The fuel pressure regulator is increasing pressure to account for the dropping vacuum in the manifold, trying to keep that perfect spray pattern going.

So... why does it work pretty darn good with the line disconnected? Because the fuel injection system can adapt and increase the dwell of the injection to account for low differential pressure. This will make the engine run, pretty decently, really. But, the spray pattern is degraded and so is mileage.

Anyway, that's what I read. It makes sense to me....