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Car Forum / Ford / Ford Trucks / October 2008F-150 gasoline smell
Hello, I am intermittently smelling gas in the cab of my 1996 4.9L 2wd F-150. The first few times it happened, there was another explanation, but it almost has to be from my truck. I am no expert, but the closest thing I can think of was a long time ago when a friend of mine started smelling gas from his car, and it turned out to be a bad fuel pump that was spraying gas, and was told "they do that so you know to replace it." My truck has two fuel tanks, and I _think_ this happens with either tank selected. Any ideas? If this is something that can be reliably diagnosed (I have LOTS of respect for gasoline vapors!) and is not terribly complicated to fix, I might take a crack at it. I'm just beginning to look into it, but wanted to post ASAP to get your thoughts on what it might be and how to approach it. To date, I've worked on small engine carburetors, and replaced shocks, the thermostat, hoses, radiator, heater core, and water pump, not quite in that order. All went well, but a master of the trade I am not. Bill > Hello, > [quoted text clipped - 17 lines] > > Bill You've got a leak somewhere. Inspect all of the fuel lines. >> Hello, >> [quoted text clipped - 19 lines] > > You've got a leak somewhere. Inspect all of the fuel lines. Sounds like a good place to start. I am just starting to read up on how to not kill myself and the truck in one big fireball, and have a couple of quick questions. First, on relieving the fuel pressure. I actually knew about this, and remembered how to do it :) However, do the two fuel tanks add any wrinkles? After defeating/disconnecting the inertia switch, do I need to run to stall (and crank for a bit) with one tank and then repeat with the other selected? I doubt that would hurt anything?? Depending on how everything works and which lines I disconnect, it could be an important step. Would there be any value in looking at fuel pressure after shutting off the engine? Haynes (I start there and then check the shop manual before actually attacking the truck with wrenches) documents various pressure tests, and a minor leak might show itself as a failure to hold pressure after the pumps stop. I called AutoZone, and they do not have a rentable gage set, but they do sell ($40) a gage to connect to the Schrader connector on the fuel rail. If that will tell me anything, I'm willing to shell out for it, if only to verify that it is working properly after I mess around with it. My pressure tester was invaluable when working on the cooling system, and the fluid in this case is an explosive. However, if there is something else I should get instead (perhaps with adapters to connect in other places, to other vehicles, etc.), please let me know. Bill >> You've got a leak somewhere. Inspect all of the fuel lines. > > First, on relieving the fuel pressure. I actually knew about this, and > remembered how to do it :) However, do the two fuel tanks add any > wrinkles? Not sure about the 96, but my 89 dual tank had 3 pumps, one low-pressure pump in each tank, and one high-pressure pump on the output of the selector valve which pressurized the fuel rail. Relieving the pressure on the fuel rail was enough. The high pressure pump was located on the frame rail below the cab. > Would there be any value in looking at fuel pressure after shutting off > the engine? Haynes (I start there and then check the shop manual before > actually attacking the truck with wrenches) documents various pressure > tests, and a minor leak might show itself as a failure to hold pressure > after the pumps stop. Sure. But a leak large enough that you can smell it should be visible. Although it may be in a line or connector that is hard to get to. David, >>> You've got a leak somewhere. Inspect all of the fuel lines. >> First, on relieving the fuel pressure. I actually knew about this, and [quoted text clipped - 6 lines] > on the fuel rail was enough. The high pressure pump was located on the > frame rail below the cab. I _think_ I read that my in-tank pumps deliver high pressure, but I will look again with that in mind. It sounds as though anything not described as "high pressure" is safe to open?? >> Would there be any value in looking at fuel pressure after shutting off >> the engine? Haynes (I start there and then check the shop manual before [quoted text clipped - 4 lines] > Sure. But a leak large enough that you can smell it should be visible. > Although it may be in a line or connector that is hard to get to. Fair enough. I'll probably blow for the gage, if only as reassurance that I didn't make it worse. You raise an excellent point about things that are hard to see. At least with my cooling system, fixing one leak turned a smaller one into "the biggest" leak - a couple of times :) By visible, do you mean gas dripping out? Or should I expect to see some residue? Thanks, Bill > David, > [quoted text clipped - 33 lines] > > Bill Even the high pressure lines are only 40 psi or so. As soon as you start pulling the connector, some gas will leak out for a second, then you're done. It's not like it's going to explode out of the connector or anything like that. Warning: don't disconnect any fuel lines unless the engine is stone cold. David, > Even the high pressure lines are only 40 psi or so. As soon as you start > pulling the connector, some gas will leak out for a second, then you're > done. It's not like it's going to explode out of the connector or > anything like that. They always make it sound worse that it is, but I'm happy to play along with most recommended procedures, if only for practice. I have noted that Haynes says to cut the inertia switch and stall the engine; the shop manual says to bleed it through a pressure gage into a container. I think I know where the Schrader connector is, but have not yet seen it. > Warning: don't disconnect any fuel lines unless the engine is stone cold. Gasoline deserves respect. No arguments. I found a few things: there is a pretty healthy leak from or near the fuel vapor canister. It seems odd that I did not notice it on my last couple of "is that coming from my truck?" searches. Maybe it's getting worse. Maybe it was simply that all I did was crank the engine and back up a 10 ft to get a clear path to the fuel lines, and then opened the hood. I am grounding the truck until I get this under control. AutoZone referred me to a bone yard; Advance was more helpful, but they need to order a canister. I am not fully convinced the canister itself leaks. In the area, there is piece of fuel line that looks ok, what looks like a piece of the drain line (similar to that which goes from the radiator to the coolant reservoir) that looks like it has seen better days, and a formed 90 degree hose that also looks like it might want to be replaced. Would you start with them, or just replace the whole thing ($70-80 or so - not sure if the mentioned hoses are part of it yet). A different AutoZone store (across town - the local guys are usually good...) told me that there should not be anything but vapor in the area, and to look at: (1) gas caps; (2) check the fuel pressure regulator. I should also mention that the hose/tube running going from the canister to what I suspect is EGR equipment, is the one that keeps coming loose toward the back/top of the engine. Re gas caps, I loosened them, and noted some escaping fumes, perhaps more than usual. The rear cap even had a trickle of gasoline coming out, which is not normal. I was very low on gas in the front tank, probably because of the leak I'm sad to say, and switched to the rear. The gage indicated it was past full. At the time (yesterday), I thought maybe that was my fault for not believing the automatic cutoff on pump, but now I am not so sure. Could it be as simple as bad gas caps? If so, what about the leak near the canister? If anything, I'd have hoped to see gas higher up, at the connection I know to be flaky, right? Jumping ahead a little: if the pressure regulator turns up bad, how hard is that to replace? I think the procedures are saying that the rail has to be removed, taking the injectors with it, and that in turn means that the upper intake manifold has to come off. Is that true? Looking around, it is easy to believe. I will keep reading in terms of what tests I need to do to identify the failure. Some of those tests look like good things for me to do, if only for the experience. I question whether replacing the regulator (IF it comes to that) is a good next job for me. The water pump and radiator turned out to be fun to replace - I got a little tired of driving across town for "the next part", but other than that, it was a blast. How much harder is it to replace the regulator? I will take a long look at the manifold and the vacuum hoses etc. over it. If it's just a lot of marking hoses and finishing off with a torque wrench, I can probably handle it. I would prefer to start with the power steering pump, about which I have a few doubts (something appears to be leaking very slowly), but gas leaks take priority. Bill All, At a minimum, I want to run through the diagnostics to try to isolate the problem. I am still undecided on whether to fix it myself. Assuming the problem is the regulator (clearly I need to test it), of "the stuff in the way," the upper intake seems the worst of it. Staring at the vacuum hoses, with labels, notes and some pictures, I could handle it. The intake appears to be held with threaded studs and nuts above and below the gasket joint. Is there any trick to that? What about wrench clearance? The front and particularly the back look tight. Any wisdom about what I might face would be greatly appreciated. The rail would come off and take the injectors with it. If I am reading correctly, the injectors are simply pressed into the rail?? What about the other end? Are they just sealed with o-rings and held in place by the rail? The regulator/rail connection looks like a gasket and a couple of screws. Having hassled with lawn mowers, I should be able to get that right. Would I be able to do a meaningful leak test on the re-installed rail w/o reinstalling "everything"? What I have in mind is getting the rail back in place, connecting the fuel lines, and turning the key on to run the pumps, quickly check for leaks, and then see how well it holds pressure via a gage on the rail. I would hate to put it all back and then find fuel pouring out near the rail. Obviously, all of this is contingent on diagnostics pointing to the regulator. The tow vs. DIY decision requires some research and soul searching, which is the subject of this post. As for my experience level, I would not hesitate to re-do the water pump, radiator, heater core, thermostat. Ditto shocks. I know because I replaced them in the past couple of years. I was planning to hunt down and fix a suspected (and slight) power steering fluid leak as my next adventure. Your thoughts on the obstacles involved in a pressure regulator replacement vs. what I have already done would be appreciated. Bill Hello all, Over the weekend, I bought a fuel pressure gage, found the port, learned how to bleed the pressure, etc. and did a few first engine-off test cycles. The pressure was very low (15 psi) the first time, and 40 psi or so after that; Haynes says to expect 50-60 psi. With the ignition turned off, it seems to hold whatever pressure it generates fairly well. At a minimum, my gage connection is not leaking, nor are the injectors, lots of fuel line is ok. I am not yet convinced the regulator is the problem (and am starting to suspect it is not), but looked at what I would be getting into if I were to replace it. Haynes suggests that it can be done with the intake in place on some models, and mine looks like one of them. I find two Allen-head screws, not three, and there was enough clearance to remove the vacuum line. Yes, there could be "hidden" screws, but the shape of the plate on the regulator strongly suggests otherwise. There is no gasoline in the vacuum side of the regulator; that does not mean much, but finding it would have been bad. I am also starting to think that I could successfully remove and replace the intake if necessary. Another look at the bolts holding the two parts together reveals that they are different than I first remembered. They look like bolts with a threaded section "on top" (actually pointing down when installed) allowing another nut to hold a few things under the intake. I think I can get to all of them; the one in the back is a little hard to reach. If you have removed an upper intake, I would appreciate the voice of experience on any gottchas along the way. Taking everything at face value, the truck cross-filled into the rear tank. I assume that had to have happened when running on the front tank. If I understand things correctly, the selector switch (1996) powers one pump or the other, and the pump that is off is expected to refuse returning fuel. I _think_ that suggests the rear tank has a stuck open return. That would explain the low pressure up front, and the cross-filling. Is there a good/safe way to prove that? Suppose I siphon some gas from back to front - I have a little hand-pumped plastic gizmo that will work. If I hotwire the pumps to stay on per the diagnostic procedures, and if my suspicion is correct, it would begin to cross-fill again. Based on flow specs, I should be able to decide how long I can let that happen before flooding the tank, and after undoing the hot-wiring, I could use the selector switch to see if the front tank level drops and the rear tank level rises. Is that reasonable, or a plan to win a Darwin Award? I further assume that the gas pouring out from/near (didn't let it happen long enough to track it down) the vapor cannister was a result of finally over-filling the rear tank. Looking at where the gas cleaned the cannister, there could be a portion of the top seam that has failed, but the hoses look pretty bad too. Is there a way to leak-test the cannister? I am still identifying parts. My next goal is to locate the DLC and STI connectors. Before I short something to ground, I need to be sure I have the correct connector. Suppose for the moment that the rear pump is the culprit. I would welcome suggestions for safely (if possible) rigging the truck to run on just the front tank. Doing that would allow me to drive vs. tow it to my trusted mechanics. It would also allow me to take the offending tank someplace (perhaps them) to be cleaned if I decide to fix it myself. How does one clean a fuel tank? It sounds like a good idea to do so before dropping a new pump in it. Replacing a pump sounds like using a jack to drop the tank, knocking loose a ring with a BRASS punch, old pump out, new pump in with some attention to a gasket, and putting the tank back. There must be some trickery with the lines - something along the lines of lowering enough to get access but not enough to break stuff. How far is that? Also, would it be easier to remove the bed to get to it? If so, how hard is it to put the bed back on the truck? Bill o-rings on the fuel injectors?.............look and see if they are wet?...........easy fix, >>Hello, >> [quoted text clipped - 19 lines] > > You've got a leak somewhere. Inspect all of the fuel lines. A little more on possible causes: just below and inside the battery there is a part that looks a lot like a drawing I saw of the fuel vapor cannister. The drawing had me thinking the cannister was not mounted in the engine compartment, but I am still trying to identify parts, which is usually the hardest step (for me anyway) of most repairs. Whatever the thing near the battery is, going from it back and up to what I think is EGR/emissions "stuff" is a tube the slips into an almost foam-like tube on something that looks like a filter. Clearly I have to learn my way around, but the point is that the foam is pretty badly dry rotted, and the tube keeps slipping out of it. So far, auto stores have told me "that's a dealer part" and I was too busy to check further. Could that be the source of the smell? Sniffing the end will be a good place to start, but I need to move it to be able to reach that far. Time to run, then I can play with truck. Bill |
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