Fuel Fuel Leak And Lovely Smell...

Justin87 · Oct 29, 2017

Hello all!

It's getting cold here in south eastern Wisconsin so this last weekend I decided to put the car into storage.

Did all the usual stuff, cleaned it out, changed the oil, checked and topped off the coolant, filled the gas tank and added Sta-bil. Then I put the car on dollys and (with a great deal of pushing and swearing) I pushed the thing into the side of my garage.

This proved to be a fools errand because the next day when I went into my garage it REAKED of gas. I checked under the car and the gas tank was damp with gas. Didn't see any specific place that was leaking from, Fuel lines and filter look good, but I do have a couple questions to help me figure this out.

1. I filled the tank including a slight top-off (which normally I don't do) is it possible I just overfilled it? If so, what are some common spots these cars leak from? Do they have some kind of a fluid vent that perhaps it's just leaking out of?

2. The car has an aftermarket fuel pump. (225 lph) and a metal gas tank(I thought the original was plastic). The work order I have from the previous owner says that the pump, tank, and associated gaskets where replaced at some shop in Michigan where I bought it. If I need to check any of that work, other than dropping the tank, is there anyway to access the pump and any of those gaskets?

I've only owned the car for a couple months and have only driven it on nice days and whatnot so I've never filled the tank before. It's had up to 3/4 of a tank full with no problems. My exhaust is dumped well away from the rear end so I am wondering if I should just run the car for a while and try to burn up some fuel. Cold temps and snow are not to far away so I'd hate to pull the thing out of storage considering I just put the dang thing in there.

Anyways, just looking for some input.

jrichker · Oct 29, 2017

You get to drop the fuel tank to find the leak unless you are very luck while doing an inspection with the car up on jackstands.

Here are some useful tips...

I have done the tank removal three times, and the main issues are getting the car up on jack stands and getting the gas out of the tank. DO NOT try to do this job without jack stands. Becoming a pancake is not part of the repair process.

Pumping out the old gas:
If the old pump still works, you can use it to pump the tank out.
1.) Separate the pressure line (the one with the Schrader valve on it) using the fuel line tools.
Look in the A/C repair section for the fuel line tools. They look like little plastic top hats. You will need the 1/2" & 5/8" ones. The hat shaped section goes on facing the large part of the coupling. Then you press hard on the brim until it forces the sleeve into the coupling and releases the spring. You may need someone to pull on the line while you press on the coupling.

OR

View: https://www.youtube.com/watch?v=vRTjYAxvaCs

Use a piece of garden hose to run from the pressure line to your bucket or gas can. Make sure it is as leak proof as you can make it. Fire and explosion are not part of the repair process...

2.) Jumper the fuel pump test point to ground.

Turn the ignition switch to the Run position. the fuel pump will pump the tank almost dry unless the battery runs down first.

Some 5 gallon paint pails lined with garbage bags are good to hold the gas. The garbage bags provide a clean liner for the pails and keep the loose trash out of the gas so you can reuse it. If you decide to use a siphon, a piece of 1/2" garden hose stuck down the filler neck will siphon all but a gallon or so of the gas.

Remove the filler neck bolts and put them in a zip bag. Disconnect the supply & return lines by removing the plastic clips from the metal tubing. If you damage the clips, you can get new ones form the auto part store for just a few dollars. I have used tie-wraps, but that is not the best choice. Then you remove the two 9/16" nuts that hold the T bolts to the straps. Put the nuts in the zip bag with the filler bolts. Pull the plastic shield down and away from the tank. Once the tank drops a little bit you can disconnect the wiring for the pump & fuel quantity sender.

The pump assembly comes out by removing a large metal ring that unscrews from the tank. You are supposed to use a brass punch to tap on the ring so that you don't make sparks. Look closely at the rubber O ring gasket when you remove the sender: it is very easy to damage on reinstallation. If it gets damaged, the car will smell like gasoline when you fill the tank up. The pump assembly requires some twisting and turning to get it out the hole.

Look very closely at the electrical wiring. The stock fuel pump wiring can overheat and melt the insulation. Mine had some really crummy plastic tubing slid over the quick disconnects. If the wires ever got together, there would be sparks inside the fuel tank and no more Mustang. I eliminated the splice in the middle of the wiring and went straight from the pump to the feed through connectors for the wiring. It required some soldering and crimping of new tabs on the wires, but it made a neater job.

Inspect the pump mount to metal tubing bracket. Mine broke and I couldn't get it to solder back together. I drilled a small hole for a machine screw & self locking nut to hold the clamp and bracket together.

The pump is easy to get off the mount but is somewhat difficult to get back it the tank without damaging the sock filter or tearing it on the tank baffle. When you install the metal ring that holds the pump in place, watch out for the gasket O ring. Some RTV may be helpful if the ring is not in excellent condition.

The tank to filler pipe seal is a large rubber grommet. Inspect it for hardening, tears and damage. At $20 from the Ford dealer, it might be a good idea to replace it.

I used a floor jack to help lift the tank back in place. A piece of ¾” plywood cut to about the same size as the tank will help insure that you don’t damage the tank by using the floor jack to lift it in place. You may find that it is the only time you really can make good use of a helper.

Justin87 · Oct 29, 2017

WOW, that level of detail is certainly appreciate!

So basically there is no scenario with any kind of excess fluid vent or something that could just be leaking from an over fill eh?

Even with something like a filler neck gasket (assuming I could pinpoint that) you need to drop the tank?

I just feel like it would have been leaking gas and smelling this entire time and it just happened yesterday when I topped it off for storage.

General karthief · Oct 29, 2017

It is possible that the filler neck gasket is bad but usually you get a wiff occasionally as a hint. You should see it looking under right side of the tank, otherwise your likely dropping the tank,
It could be too full and a bad vent tube, jack it up, stick some jack stands under it like suggested above and give it a good once over, and air out that garage before plugging in or turning on any lights

Mustang5L5 · Oct 30, 2017

Crawl under the pass rear side of the tank area. You'll see the filler neck and its seal and should be able to tell if it's leaking.

The tank vent is in very top..hard to leak gas from there

Here's pass side of tank. You can see filler neck seal, and the small vent on top

General karthief · Oct 30, 2017

The glaring, unpainted vent on top

Justin87 · Oct 31, 2017

Mustang5L5 said:
Crawl under the pass rear side of the tank area. You'll see the filler neck and its seal and should be able to tell if it's leaking.

The tank vent is in very top..hard to leak gas from there

Here's pass side of tank. You can see filler neck seal, and the small vent on top

Had the car on a lift today (my buddies shop) and fuel is coming down from the top of the tank. Not really concentrated on one side or the other.

The thing I keep coming back to, is that I've had ZERO smells or drips until I filled the tank up.

Justin87 · Oct 31, 2017

karthief said:
The glaring, unpainted vent on top

Considering I'm about to put the car into storage for the winter I'm considering just draining the fuel back down to a half tank before I had the issue and worrying about the rest of it come spring.

General karthief · Oct 31, 2017

The o ring for the pump/gauge is likely broken or pinched, I'd have to fix it befor I store it but it's your call.

Mustang5L5 · Oct 31, 2017

O ring for pump is usually high enough to not have to worry. I would suspect fuel level sender o ring, or a puncture?

Justin87 · Oct 31, 2017

Mustang5L5 said:
O ring for pump is usually high enough to not have to worry. I would suspect fuel sender o ring, or a puncture?

Your suggestion about a puncture is interesting tho, because it is a new-er gas tank and if it has a bad seem that could cause it to leak only after I filled it to a certain point.

Today, I did have a smoke pressure test done with the system still in the car, and it wasn't enough to produce a leak unfortunately. The next step would be to drop the tank (as you mentioned earlier) which I'm not against, it's just getting cold, and again, I'm trying to put it in storage.

Probably delaying the inevitable at this point.

imp · Oct 31, 2017

Justin87 said:
Your suggestion about a puncture is interesting tho, because it is a new-er gas tank and if it has a bad seem that could cause it to leak only after I filled it to a certain point.

Today, I did have a smoke pressure test done with the system still in the car, and it wasn't enough to produce a leak unfortunately. The next step would be to drop the tank (as you mentioned earlier) which I'm not against, it's just getting cold, and again, I'm trying to put it in storage.

Probably delaying the inevitable at this point.

Might it be possible that being outdoors, cold, when you filled the tank, then put it indoors, the volume increased enough to start leaking due to expansion? Especially if the fill-cap check valve leaked. Just a thought. imp

Mustang5L5 · Oct 31, 2017

You really only have 4 potential leak places before you must suspect the tank.

Filler neck seal is easy to see and rule out.

Vent and fuel punp seal are highest part of tank and hard to leak unless the seals are really blown.

Fuel level sensor could be under the full level if you really top off the tank as the pass side bulge for the filler is higher than rest of tank. If one of the 4 were to leak and not be the filler neck seal, this would be my second guess.

I'd siphon the tank down a bit and wait for spring...unless you just want to address it during the off season. But either way tank needs to drop

2000xp8 · Nov 1, 2017

Not to try and an insult to injury, but why would you top off the gas tank to store the car?
If anything i'd want like 1/8 of a tank, this way I could put fresh 93+ in it in the spring.

General karthief · Nov 1, 2017

It's been a while but doesen't stalbil say to fill the tank?
I don't think I would store a full tank but then I don't store my car, here in the sunshime state I drive my junk year round.

Mustang5L5 · Nov 1, 2017

I usually park it with whatever it happens to have. My car sat 10 years with half a tank and when I recent took it apart, the insides looked brand new with zero corrosion. if all the seals are good there isn't an issue with corrosion, but you might waste gas if it happens to go bad.

Since I just replaced the tank, I'll toss 1-2 gallons in and call it a day. I don't even bother with stabil. I mixed gas for my weedwhavker 2 years ago and still using it and it starts first pull.

I think my Harley still has 2 year old gas in the tank. Still starts up when I started it for the first time this year 2 weeks ago

MFE92 · Nov 1, 2017

The most common suspect is the fuel filler neck grommet.

Justin87 · Nov 1, 2017

2000xp8 said:
Not to try and an insult to injury, but why would you top off the gas tank to store the car?
If anything i'd want like 1/8 of a tank, this way I could put fresh 93+ in it in the spring.

I suppose it's different strokes for different folks.

As I kid, I grew up with a couple old Mopars, and when my old man would store them for the winter he would fill the tank, and put Stabilizer in it. So, I've always done it that way too. Never had any starting issues come spring with my old 84, or my pervious 90GT.

On the bottle, Sta-bil also says to add product, fill the tank, and then let idle for 5-10 minutes before storage. So that's what I did but unfortunately here we are.

88LXSleeper · Nov 1, 2017

I agree with filler neck grommet, with tank being overfilled in cold temp fuel will expand when warmed up in garage. Tank should be kept near full to prevent condensation on bare tank walls.

imp · Nov 2, 2017

Mustang5L5 said:
I usually park it with whatever it happens to have. My car sat 10 years with half a tank and when I recent took it apart, the insides looked brand new with zero corrosion. if all the seals are good there isn't an issue with corrosion, but you might waste gas if it happens to go bad.

Since I just replaced the tank, I'll toss 1-2 gallons in and call it a day. I don't even bother with stabil. I mixed gas for my weedwhavker 2 years ago and still using it and it starts first pull.

I think my Harley still has 2 year old gas in the tank. Still starts up when I started it for the first time this year 2 weeks ago

What yer sayin' is that unleaded gasoline turning sour is bullsh!t, then? Gotta agree. My hacks out here have stood untouched several years, the '72 Ranchero started up with a bit of ether on the old, rotten fuel in the tank! imp

Fuel Fuel Leak And Lovely Smell...

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