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  1. #1

    Default Fuel System Problems Revisit

    Alright, so i was talking to Fastlane about my fuel system problems in his build thread, and thought i would start a new discussion rather than hijack his thread any further. Here's the conversation.

    Quote Originally Posted by Fastlane View Post
    Using the 87-93 Fuel Injection Lines on the LTD are a different story, I first attempted to bend the old lines to fit, but it needed several bends and once done it looked like crap, so I ended up purchasing some new 5/16 and 1/4 line along with some tools to bend and cut the lines . This was a learning experience so I ended up wasting several feet, but the Tube is cheap (25 feet is around 25-30 dollars).
    I did use some of the Original Fuel Injection tubing, but only to where goes under the fender and connects underneath near the sub frame, from there I used new tubing. To connect the old and new tubing together I used a "Fuel line Compression Union", which worked fine, no leak issues at all. Just make sure if you use these that they are made for fuel. This type of Compression fitting it all brass, so the fuel wont break it down and cause it to leak.
    https://www.amazon.com/Dorman-800-22...n+800-222+Fuel

    I may end up replacing with Stainless steel Flex line, but this works fine for now.
    Quote Originally Posted by ZephyrEFI View Post
    Interesting. I scrapped the Mustang fuel line as well and went to -6 braided stainless. I'm not sure if that's too big or what, but I've never been able to get my fuel system to work well. The fuel pressure always drains back after i shut the engine off, despite going through several fuel pumps and regulators. I'm pretty sure the problem is on the pump side, so i have yet another pump waiting to go in. I just hate pulling the gas tank. I also have a vapor pressure build-up problem. I can't pump gas into the thing without it spitting back at me. SO frustrating. I know i need to fix it; I'd rather not blow up if I can help it.
    Quote Originally Posted by Fastlane View Post
    In my case the only thing wrong was an old pump I used. Once the engine was shut off, the pressure drop right away. The new pump holds the fuel pressure for several hours after the engine is shut off, which is what it should do.

    Will the LTD LX Fuel Tank Fit into the Zephyr? Its a 20 gallon tank, but comes with the correct Vapor Valve which connects to the Vapor Canister and the fuel pump sits in the tank like the mustang. The Vapor Valve I believe is what keeps the fuel pressure stable, and if its not part of the fuel system this may be what is causing the problem with the Zephyr.
    Actually I do have an LTD tank in my Zeph. It's from a wagon because those are the same as '78-81 F/Z and Granada/Cougar tanks just with the provision for the in-tank pump. Later F/Zs, and LTD/Marquis sedans went to a "deep well trunk" and used a different tank. I retrofit the high pressure pump onto the low pressure LTD pump hanger, much the same way I'm sure you did.

    The vapor valve is there, and brand new. the vapor line going to the engine bay is mostly new. All the seals on the tank are new. THE TANK ITSELF IS NEW! The only things that aren't new are the filler neck, which is not available new, and the carbon canister and purge solenoid/valve.

    I could buy a new carbon canister and solenoid, but that's almost $100 and I've blown so damn much money on this so far with no result. And the solenoid does not throw a code.

    That said, the tank vapor valve being new does not guarantee it works (my fuel pump roulette has taught me that), i suppose. But i don't really know how to test it. I tried blowing into it, but that didn't do anything. I know it's not the gas cap, since i have the symptom (gas spitting back at me) when the cap is off. I suppose one possibility is the air passage in the filler neck. I can't say with absolute certainty it's clear (although i don't see how i could have missed that).

    I'm hesitant to go to the trouble of pulling the tank because of the possibility I'll put it back together again and it still won't be fixed. That would be a HUGE letdown.

    Any ideas?
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI T-5 (Mustang LWB)
    '17 Ford Transit Connect Titanium LWB
    '14 Ford Fusion SE Manual

  2. #2

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    Pretty please? Beuller?

    This is really the one thing that keeps me from enjoying this car.

    I found an LTD wagon being parted out on ebay and i have a question in to the seller whether he will sell me the filler neck and the plastic box thingy that the filler neck sits in and bolts to just inside the filler door. So that would potentially solve any odd angle issues with the filler neck into the tank. I don't think that's really an issue, but just trying to cover my bases.
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI T-5 (Mustang LWB)
    '17 Ford Transit Connect Titanium LWB
    '14 Ford Fusion SE Manual

  3. #3

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    http://www.ebay.com/itm/1987-1993-Mu...g/142057847930
    When you setup the Fuel Injection Tank, did you include this filler neck Box? Notice the hose attached, this is what should relive the pressure when you go to fill up the tank. If this hose is plugged up or missing, this may be what is causing the problem on you Zephyr.
    1985 Ford LTD LX
    1989 Mustang 5.0 Coupe
    1994 Ford F150 Lightning

  4. #4

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    Well my one of those does have that hose, but I think it's function is actually a drain for when any fuel gets in there during filling. When i fill, I see fuel spilling on the ground from it coming back up the filler neck. I thought what i was seeing was a leak somewhere on the tank, but I'm pretty certain I there's no leak. The filler neck is split inside though, and I believe the escaping air comes out via the top 1/3 or so of the filler neck. At least part of the escaping air. I think what I'm getting is fuel coming back up that part of the filler neck because the vapor vent valve and lines aren't doing what they're supposed to for some reason. It's possible that top part of the filler neck that's supposed to allow air to escape is plugged, I'm not 100% certain it isn't, but I'll be REALLY surprised if it is. I've had this crap in and out so many times, i don't see how i could have missed something like that.
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI T-5 (Mustang LWB)
    '17 Ford Transit Connect Titanium LWB
    '14 Ford Fusion SE Manual

  5. #5

    Default

    you are right on the hose and tube, this appears to just be an over flow release, so if its plugged it should not effect the tank. Looking at an 87-89 filler neck, you can see at the bottom piece that sits in the tank, is split.

    At the top right side, next to the filler hole is a another hole, much smaller (you can just see part of it in the picture), this appears to be what releases the pressure while you fill the tank.
    1985 Ford LTD LX
    1989 Mustang 5.0 Coupe
    1994 Ford F150 Lightning

  6. #6

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    Agreed. I just need to get some time to pull that bastard (gas tank) out and see what's what. I might get some time on Friday.
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI T-5 (Mustang LWB)
    '17 Ford Transit Connect Titanium LWB
    '14 Ford Fusion SE Manual

  7. #7

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    its these simple parts you don't think about that seem to cause the most problems.
    1985 Ford LTD LX
    1989 Mustang 5.0 Coupe
    1994 Ford F150 Lightning

  8. #8

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    Yeah... I'm really at square one here. Admittedly, I haven't done as much real diagnosis and repair verification in the past as I should have, obviously. I just have a little problem with patience, and i only have so much time. I get so anxious to get the car back on the road, rather than torn down. "this has got to fix it!" well, nope.
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI T-5 (Mustang LWB)
    '17 Ford Transit Connect Titanium LWB
    '14 Ford Fusion SE Manual

  9. #9

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    I suppose that is why a lot of us have more then one car to work on. If you get frustrated on one you can work on another, sometimes working on something else helps figure out the problem you had on the first car.
    1985 Ford LTD LX
    1989 Mustang 5.0 Coupe
    1994 Ford F150 Lightning

  10. #10

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    Yeah, i need to be able to walk away if I'm just not getting anywhere. That's why I didn't make a good dealer mechanic.

    I've been kicking around the ideas to buy a new carbon canister and purge solenoid just so i can be more sure those are working the way they're supposed to, as well as make a new metal vapor line, again "just to make sure". I'm sure I'm getting ahead of myself though. The weather's been really nice here for the past week, so it's got me thinking about spring car shows. We're supposed to get slammed with bigtime snow on Friday though.
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI T-5 (Mustang LWB)
    '17 Ford Transit Connect Titanium LWB
    '14 Ford Fusion SE Manual

  11. #11

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    So what problem are you having exactly? Fuel drain back, and it spews fuel out when you try to put fuel in it? The fuel pressure leaking down could be the fuel pressure regulator. I wouldn't waste my money on a carbon canister or emissions stuff.
    1978 Mercury Zephyr 418 sbf w/ glide E-100 and Nitrous. Mid 5's @ 124 on 26x10's
    1986 Ford LTD street car w/ turbo. Best et/mph so far 10.5 @ 140 on 17" hard tires. Driven to and from track.

  12. #12

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    Quote Originally Posted by 408GT View Post
    So what problem are you having exactly? Fuel drain back, and it spews fuel out when you try to put fuel in it? The fuel pressure leaking down could be the fuel pressure regulator. I wouldn't waste my money on a carbon canister or emissions stuff.
    Well, yes, both, but the one I'm really looking to solve is the pressure build-up in the tank when I'm filling problem. I'm guessing that's not the only time my fuel tank is building too much pressure, and that seems not so good to me. In another thread where i was discussing this, a guy suggested I try gently building pressure via the filler neck with compressed air and see if the vapor vent valve and the rest of that system (vapor line, carbon canister, etc) is actually doing what it's supposed to. That seems like the most likely culprit, despite the fact almost all of that system is new parts, except the carbon canister and purge solenoid.

    The drainback problem is mostly just an inconvenience, but it doesn't scare me like the pressure problem does.
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI T-5 (Mustang LWB)
    '17 Ford Transit Connect Titanium LWB
    '14 Ford Fusion SE Manual

  13. #13

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    You may have already seen this, http://vb.foureyedpride.com/showthre...pics-warning!)
    He has some good information on the Gas Tank.
    1985 Ford LTD LX
    1989 Mustang 5.0 Coupe
    1994 Ford F150 Lightning

  14. #14

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    Alright, so i spent some time poking around with my filler neck today, and i am confused. if you look at the bottom end, it's split, just like the Mustang one above...


    This is what the top looks like.


    If you open the filler hole, the other vent holes next to it are open to the same bottom half of the filler neck as the filler hole. I tried sticking some mechanic's wire up the top half of the filler neck, but i couldn't get it to go anywhere. I guess my hypothesis about what the top half of the filler neck for is wrong. Maybe it's just a size thing to affect the pressure to make the gas station pump click off or something. No idea. Anyway, that's all i got done today. I haven't gotten the chance to try the air pressure test i was going to do.
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI T-5 (Mustang LWB)
    '17 Ford Transit Connect Titanium LWB
    '14 Ford Fusion SE Manual

  15. #15

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    This is a pic posted by 4 Barrel Mike of a Mustang filler neck next to a F/Z filler neck. I might try that if i can't find anything definitive when I try to diagnose this on Friday.



    They seem to be really close, and Mustang filler necks can be had new.
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI T-5 (Mustang LWB)
    '17 Ford Transit Connect Titanium LWB
    '14 Ford Fusion SE Manual

  16. #16

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    Alright, so I did some diagnosis today. I tried the thing where you seal up the end of the filler neck and see if you can pressurize the tank with compressed air. The vapor vent valve is doing its job. The vapor line is doing its job, and the carbon canister is doing its job. Although I was able to build pressure in the vapor line with compressed air pretty easily. Air can and does pass through it though. Same deal with the vapor vent valve. If i build pressure in the tank, air starts escaping almost immediately from the vapor vent valve, but not quickly enough for air not to need to escape also from the little hole in the filler neck i'm pushing air in with. I pull my blow gun away from the hole and air slowly escapes from both the vapor vent valve and the hole in the mostly sealed off filler neck.

    So where do i go from here? Everything seems to be working, but maybe just not as well as it could be. Do I make a new, larger vapor line to allow more air to escape? Will that even make any difference if the vapor vent valve can only allow so much through? The time i'm having a noticeable symptom is when I'm filling. Is maybe the filler neck not pulling its weight allowing enough air being displaced by fuel to escape? As far as i can tell the filler neck is fine. Any ideas? I'm counting on you, FEP!
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI T-5 (Mustang LWB)
    '17 Ford Transit Connect Titanium LWB
    '14 Ford Fusion SE Manual

  17. #17

    Default

    Still needing some direction on the vapor problem. I'm going to play with it some tomorrow, pouring gas in with the vapor line removed to see if that's what's causing the bottleneck relieving the pressure or not. What I don't feel like i have that good of a grasp on is, how important is the vapor recovery system in the gas station fill situation? Is it that system, or the venting built in to the filler neck that's intended to allow most of the air to escape as you are pushing air out as you pump fuel in? If I had to guess, I'd imagine you're probably dealing with mostly fuel vapors coming out of the tank like that, as opposed to normal air, so you'd probably want the vapor recovery system to do the most here. But I don't have a good enough understanding of all that. If that's the case, why does the vapor vent valve seem to be allowing so little out with my little pressure test?

    Anyway, I decided to go ahead and order a new Mustang filler neck since they're relatively cheap ($36) and compare it to the ones i have on hand. Here it is with my original 1979 larger diameter filler neck.


    Next, i decided to try and show the difference in vertical difference between them, how high the fuel door sits relative to where the filler neck comes out of the tank.

    It's not perfect, but it does seem to show the Mustang's filler neck has to cover quite a bit more vertical distance...

    Here is the Mustang filler neck with the one I've been using on the car I believe is from an '82 Fairmont sedan.


    And again the vertical distance test.


    The difference doesn't seem to be as significant here, but it is still there. I see the perspective of the picture is different, so this is far from that good of a test. These two do have the same diameter though.

    It does raise some more questions. Do the F2C (LTD Wagon) tanks have the filler neck hole in the same spot as the F2A ('79-81 Fairmont/Zephyr) tanks? I believe they do. When i first installed my LTD tank, I slid my original filler neck in, and the placement of the fuel door to the top of the filler neck was spot on. The larger diameter filler neck only fit with the seal removed, so obviously I couldn't use it. What about compared to the '82-86 sedan tanks for filler neck hole location? No idea. Maybe that explains the apparent difference in vertical distance covered between the two Fairmont filer necks i have. I don't know. All I know is my head hurts and i don't know what to do about this damn problem.
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI T-5 (Mustang LWB)
    '17 Ford Transit Connect Titanium LWB
    '14 Ford Fusion SE Manual

  18. #18

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    Well, i decided trying a new vapor line will be easy enough. Here's a look at the original ('90) vapor line next to the 3/8" fuel line I'm putting in.



    Didn't get the chance to do any testing today though.
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI T-5 (Mustang LWB)
    '17 Ford Transit Connect Titanium LWB
    '14 Ford Fusion SE Manual

  19. #19

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    So, my friend Stymees'mont came to me with an idea for this. This is a '99-04 Mustang filler neck.

    Modern filler necks have separate tubes that serve the function of venting the air during filling. Why couldn't a guy do the very same thing with an earlier system?

    I was doing some poking around to see if there's any OEM parts i can use to accomplish this. Turns out Mustangs used the same fuel tanks from '86 all the way to '97 or 98. Since i bought a Mustang filler neck, I thought maybe I could make something happen here. Take a look at the '99 and up fuel tank.

    How about that. There's a nipple to the right of the filler neck hole for the very same thing I'm looking at doing.

    So what about the filler necks? Here's the one i just bought that's '82-93 application.


    Comparing apples to apples here's one from a '94-98 which is meant to go with the very same part number tank as the one I have.


    I was thinking i could use the '99 and up filler neck above because it already has the tube I'm looking at adding to mine. BUT, not so much. The '94 and up filler necks are QUITE a bit longer than the Fox ones, so I think this is a dead end. Plus, the '99 and up filler neck is a whopping $200!! Damn!

    But on the plus side, we do learn that the factory just puts a presumably open nipple there for the vent hose to attach to. No valve or anything needed. I guess I can get a little section of pipe, weld it on to my tank, do the same with the filler neck, and then run a hose between them! This should solve my problem!!
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI T-5 (Mustang LWB)
    '17 Ford Transit Connect Titanium LWB
    '14 Ford Fusion SE Manual

  20. #20

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    Brad, have you considered the possibility that the divider in your original filler neck is simply rusted through?
    Relieving tank pressure during fill-up has nothing to do with the venting/evaporative system. It's entirely done
    through the filler neck itself.

    I would also look carefully at how the lower end of the filler tube sits in relation to things inside the tank. The
    fuel has to have room to flow out after it exits the filler, or it will find another place to go, like back into the
    filler tube vent channel.
    Last edited by JACook; 03-25-2017 at 11:07 AM.
    Cheers,
    Jeff Cook

    '85 GT 5-speed T-Top, Eibachs, Konis, & ARE 5-Spokes ... '85 GT CFI/AOD Vert, all factory...
    '04 Mach-1 40th Anny, 34K original miles... '79 Fairmont StaWag, 5.0, 58K original miles ...
    65 notch, 289 auto, Pony interior ... '67 coupe 6-cyl 4-speed ... '68 Vert 307 4-speed...
    (And a 1-of-328 Deep Blue Pearl 2003 Marauder 4.6 DOHC, J-Mod, 4.10s and Lidio tune)

  21. #21

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    I have noticed on my 83 TC it will back up in the filler neck depending on what station Im at. Every part of my fuel system is new. Im willing to bet the problem is not our cars and more that the pumps now pump faster or more volume for these newer vehicles.


    Also I see more than a few people talk about the fuel pressure bleeding off once the motor is off. I am failing to see what the issue is? Does the car still start fine? My car does the same thing with dual pumps, Walbro 255 and a Aeromotive regulator. Its bleeds off immediately after its shut off and still fires right back up everytime without issue. I am actually happy it does this so I know after I walk away from my hot car the fuel system looses pressure as soon as I walk away from it. If a part of the fuel system were to fail I wouldnt want 40psi of fuel spraying all over God knows what part of the car.
    Brian R. of Michigan
    83 TBird 5.0
    88 Ranger 2.3t
    http://vb.foureyedpride.com/showthre...83-Tbird-build

  22. #22

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    In OE EFI systems, fuel pressure bleed-down is the first sign of a fuel pump that's seen better days.
    Cheers,
    Jeff Cook

    '85 GT 5-speed T-Top, Eibachs, Konis, & ARE 5-Spokes ... '85 GT CFI/AOD Vert, all factory...
    '04 Mach-1 40th Anny, 34K original miles... '79 Fairmont StaWag, 5.0, 58K original miles ...
    65 notch, 289 auto, Pony interior ... '67 coupe 6-cyl 4-speed ... '68 Vert 307 4-speed...
    (And a 1-of-328 Deep Blue Pearl 2003 Marauder 4.6 DOHC, J-Mod, 4.10s and Lidio tune)

  23. #23

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    Quote Originally Posted by JACook View Post
    Brad, have you considered the possibility that the divider in your original filler neck is simply rusted through?
    Relieving tank pressure during fill-up has nothing to do with the venting/evaporative system. It's entirely done
    through the filler neck itself.
    Yeah, that's becoming clear as I go, but I didn't know that when I started. As far as whether it's rusted through, i don't see any evidence of that's but there's a pretty large area I can't see with a flashlight.

    Quote Originally Posted by JACook View Post
    I would also look carefully at how the lower end of the filler tube sits in relation to things inside the tank. The
    fuel has to have room to flow out after it exits the filler, or it will find another place to go, like back into the
    filler tube vent channel.
    I'm fairly sure we're okay as far as that's concerned. When I first got this filler neck, it was much longer, and I've cut it down twice. It's supposedly from an '82 Fairmont according to the junkyard I got it from, so that tells us NOT a wagon. Were the filler necks the same between the wagon and deep well trunk sedans? I don't know! If only I had access to the Ford Parts Database for a day, I could learn a heck of a lot. So, I've got this LTD wagon tank and a filler neck that may or may not be the right one to go with it in a '79 sedan. I remember at first it was practically touching the far side of the tank spare tire cutout, so that was why I cut it the first time. I cut it again when the problem persisted, but that didn't help either. I think that tree has been barked up as much as it warrants. Not a definitive answer, no, but a pretty good one.

    What i would love to have is an actual '82-86 wagon filler neck, but that's the luck of the draw and I have yet to find one. As far as the bad pump thing, that was exactly what I suspected, but turned out to be wrong!

    Brian, are you saying you don't have to cycle the key 100 times to get the pressure back up before you start yours? But you're not the first guy to tell me that just seems to be part of the deal with this vintage of car and today's gas station pumps, and it does confirm what I've been finding, that there doesn't seem to be anything WRONG with any of the components. So if we want to make the problem go away, it's up to us to come up with something else to solve it.
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI T-5 (Mustang LWB)
    '17 Ford Transit Connect Titanium LWB
    '14 Ford Fusion SE Manual

  24. #24

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    Correct Brad, turn the key,ecm primes the system and fire.
    Brian R. of Michigan
    83 TBird 5.0
    88 Ranger 2.3t
    http://vb.foureyedpride.com/showthre...83-Tbird-build

  25. #25

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    Quote Originally Posted by ZephyrEFI View Post
    ...But you're not the first guy to tell me that just seems to be part of the deal with this vintage of car and today's gas station pumps, and it does confirm what I've been finding, that there doesn't seem to be anything WRONG with any of the components...
    'Ceptinfur I've got a '79 wagon that doesn't ever spit back at me. And an '81 Futura... And two '85 GTs...
    Granted, we use vapor recovery nozzles here, but with those, any spitting back will cause the nozzle to
    shut off, and THAT would just piss me off.
    Cheers,
    Jeff Cook

    '85 GT 5-speed T-Top, Eibachs, Konis, & ARE 5-Spokes ... '85 GT CFI/AOD Vert, all factory...
    '04 Mach-1 40th Anny, 34K original miles... '79 Fairmont StaWag, 5.0, 58K original miles ...
    65 notch, 289 auto, Pony interior ... '67 coupe 6-cyl 4-speed ... '68 Vert 307 4-speed...
    (And a 1-of-328 Deep Blue Pearl 2003 Marauder 4.6 DOHC, J-Mod, 4.10s and Lidio tune)

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