Exactly how much trouble would a leaky filler neck cause? like say, the rubber hose behind the fuel door that the gas travels down to the tank in has a crack in it. Would it cause crazy problems like the truck not wanting to start good on a warm day after driving it. The warmer it gets, the more apparent the problem is.

I'm thinking that it must be an excessive fuel problem the more i think about it, i just cant figure out where its coming from. Fuel pressure seems to be okay. The reason i think so is because it gets horribly bad gas mileage, like 10 miles/gallon. Also, there is a fuel smell that seems to come from underneath the drivers door. Its not a leaky fuel fitting, it might be from an exhaust leak, but the thing is is that the exhaust at the end of the tail pipe doesnt seem to smell. Both tail pipes have black soot on the inside of them. I've hooked up a fuel pressure tester, fuel pressure runs at 25, then when i unplug the vacuum line to the regulator, it jumps up to 35 PSI. There is NO fuel in the regulator vacuum line. I was thinking it could be a leaky injector, but when i shut off the truck with the pressure tester connected, the pressure stays constant. IT doesnt drop, which means fuel isnt leaking out an injector right? or will it leak such a small amount that i wont be able to tell? It also seems to run better when its cold outside, like the truck feels more powerful, it doent stumble as much when you start it after you've been driving it. I'm wondering that if something. Thats why it has to be getting too much fuel, if the air is cooler its more dense, which means that it would run better if the truck was dumping in too much fuel, and it is also why it runs like crap when its warm, because its getting all that same amount of fuel, but the air is less dense, which means it wont be burning all that fuel, hence it running rich.

 

Well, my first reaction is the concern/mention of 10 MPG when there are reasons for a fuel leak while driving. The other thing that it's going to do, assuming air is entering via the leak due to engine vacuum, is to run rich when cold. The EVAP system works when the engine is cold. With that leak you're going to be drawing air into the gas tank and over the fuel, which will find it's way into the intake. Under normal circumstances, there would only be small amounts of HC trapped in the canister which would be burned during engine warmup.

 

25 psi fuel pressure is not within specs for a '94 4.0L with regard to any part of the test. And you really should be getting closer to 40-45psi when you pull the vacuum line off the FPR:

(35-45 KOEO)

(30-45 KOER)

In EEC-IV especially, all the the gas tank-related hoses, and the filler neck and cap, matter a great deal for proper operation and venting of the EVAP system.

Have you tried pulling codes?

 

Yep, the only code i get is a 511-pcm failure, which is because of my diablo chip. So that filler neck problem could be causing my troubles? I think i'll be replacing that soon. Otherwise, yeah, its basically driving me nuts trying to figure out what the heck is wrong with this piece. My only question is why its not setting off codes via the o2 sensors. as rich as its running, you think there would be something.

 

Yes. The fuel system is sealed and the EVAP system requires this. There is potential for it to run rich under certain conditions if they system is not sealed.

I think that if it's running rich the O2 Sensors would detect it and trip a code.


What thermostat is in it? If the thermostat is not a 195 degree F one, replace it with the correct one. Running in open loop on a warm engine uses more fuel. I would also look and see if someone has removed the octane jumper and thus retarded the timing (and performance and gas mileage). I'm still wondering if that fuel neck is leaking gas on the ground while you're driving and thus killing mileage.

Out of curiosity, how are you checking mileage? Are you doing it on full tanks of gas, and ideally calculating mileage over maybe three tankfulls?

 

The filler neck hose Peter94 said is a problem, well I didn't see anyone mention that there is an inner hose too. Just an FYI if you want to replace the whole thing not to forget about the inner one too.

If the outer hose is cracked I would think like the others mentioned that the fuel system would not be able to provide the proper fuel pressure due to the leak. 10mpg is REAL bad, I got better than that when I was running my 400ci Firebird. Not by much though.

 

Hmm, i will have to go junkyard shopping come monday i guess. I wonder how much a new one of those puppies is? Yeah, mileage is being calculated on a per tank full basis, i put the nozzle in on the number one pump at holiday every time i fill up, then let it fill until it auto shuts off, get in, calculate mileage. I mean, if it only got 10 mpg once, then i wouldnt be so worried, i'd just contribute it to error, but its been multiple times, and i've been seeing it drop too.

 

Let me know what price you find for a filler hose. The outer hose on my 97 is cracked and I was constantly smelling gas. At first I thought the fuel cap was bad so I bought a new one. The gas smell was still there, so I decided to drop the tank to find out if a vent hose was bad. I found the outer fill hose cracked, so I taped it up temporarily until I bought a new one. When I called the dealer they ave me a heart attack when they said a new one is $266.00. It comes as an assembly with inner and outer hose with filler neck. Needless to say I am shopping the junkyards with no success yet. My truck is giving me a P1443 code and the mileage is around 13-14 mpg with mostly in town driving.

 

I have the same problem, when I fill the tank gas leaks out. I am getting about 20 miles to the gallon though which I guess is normal ? The outer hose has a couple of tiny slits in it, about the size to fit a razor blade through. Is there any type of patching material that I can use that is impervious to gas ? I think it's absurd to have to spend $267 for a piece of rubber. I was also maybe thinking of cutting the hose just above where the cracks are and then splicing it up top where it connects.

 

I finally gave in and bought a new one. The odor is gone, but I still get an intermittent check engine light and P1443 code. I think my cannister purge sensor is bad, but I haven't got a new one yet. It apparently is also a dealer only item. The auto parts stores I've called don't have a clue what the purge sensor is. The dealer says it is around 20 dollars I think. I was able to get a discount on the hose by buying it through my company's name. If your employer does not care, you might try it. I saved $90.00!

 

The $267 was the Ford employee price (supposedly). The retail was like $360 or something. I went ahead and just used the same hose, I haven't had any gas smell in my vehicle except when I fill the thing up all the way. It also appears that the inner hose might be offline a little bit because it was a mother effer to fill up last night, but I made it. I am thinking of replacing the hose when I get back from vacation, but it was a pain getting the tank back in the right position. I believe where I've read it is easier just to remove the bed and replace it that way, any ideas ?

 

Yes it is easier to remove the bed. Also, did your parts guy happen to mention what years that covers? I can't imagine it would be that much if you went to a junk yard and got the newest one you could find.

 

You guys have me thinking. I just bought a 1997 SuperCab 4x2 2.3 5 speed w/ about 98k miles. The first time I filled it up, the smell of gas lingered strongly for a good while. So much so that I crawled underneath. I saw what I thought might be a little residue around the place the filler tube went in the plastic tank. Since then I've been careful not to overfill the tank, and the smell hasn't been so bad after filling it. Does the outer tube carry the overflow back into the tank by chance? That would make sense with the symptoms I'm having.

Secondly, the gas mileage has been dissapointing for a truck that's EPA estimated to be 23/28. I drive basically all city miles, and have run the A/C a little extra at times. Still, my first tank was 15 mpg. I didn't specifically check the second tank, but the miles traveled on the trip odometer were about the same as the first tank, and it took around the same amount of gas to fill, so the mpg on the second fill up seems to be about the same as the first.

I have no check engine light, and I'd have expected the CEL to come on from something like a leaky outer filler tube. I mean, it'll come on if the gas cap is left off, right? Isn't a leaky tube about the same thing?

Thanks for your input!

 

***bump***

 

My dealer said the 97's would not trip the light with a leaky gas cap or hose. That started with a later model year but he didnot say which year.