Gas Smell

[sgtjd]

Just got the 1973 Mustang Mach I out of storage and notice that there is a strong gas odor emitting.
The gas cap could be changed out, but I believe it may have other things too. Any ideas?

 

[Doug's 73 Mach1]

Leaky, fuel level sender gasket, hose from same sender to steel fuel line, leaky fuel hoses below the master cylinder, or from the steel fuel line over to the fuel pump. If original steel fuel lines, corrosion hole(s) in same. If noticed after starting, leakage at the carburetor fuel filter hose or carb float(s) stuck not limiting gas being pumped into the carb. Todays gas with ethanol in it may have deteriorated the fuel hoses.

 

[tony-muscle]

I could be the normal gas vapors going up the charcoal canister, but the canister not working that well. Gas cap as you say may allow gas vapors out and get smelly if you sniff the rear of the car.

 

[mrgmhale]

I like the prior responses, but wanted to expand on the fuel evaporative control system (EVAP) a bit. The EVAP system is one of those rare emission control systems that actually does a lot of good, but it has no adverse side effects - at least when it is working properly. The biggest problems I see with EVAP systems is when folks, not understanding how it works, begin to disconnect hoses to the canister, or connect a vacuum line between the intake manifold and the EVAP charcoal canister. When the larger foil & paper vapor hose that connects the EVAP canister to the air cleaner housing is disconnected the canister gets loaded with fuel that is not sucked into the engine and burned. In severe cases so much fuel vapor os collected in the canister that is begins create liquid fuel which can start to small really strong.

I have attached some files that show how the EVAP system is supposed to be connected to the liquid/vapor separator valve on the top/front of the fuel tank that connects to a steel fuel vapor line and the other end of said vapor line ends up connecting to the EVAP canister. The canister then uses a larger foil/paper hose that leads to the air cleaner housing, where the engine creates a slight vacuum that draws the fuel vapors into the engine itself. On the canister there is a plastic hood over its went to atmosphere. It is a very simple system that really works well to reduce fuel vapors from getting into the atmosphere.

 

[Stanglover]

I like the prior responses, but wanted to expand on the fuel evaporative control system (EVAP) a bit. The EVAP system is one of those rare emission control systems that actually does a lot of good, but it has no adverse side effects - at least when it is working properly. The biggest problems I see with EVAP systems is when folks, not understanding how it works, begin to disconnect hoses to the canister, or connect a vacuum line between the intake manifold and the EVAP charcoal canister. When the larger foil & paper vapor hose that connects the EVAP canister to the air cleaner housing is disconnected the canister gets loaded with fuel that is not sucked into the engine and burned. In severe cases so much fuel vapor os collected in the canister that is begins create liquid fuel which can start to small really strong.

I have attached some files that show how the EVAP system is supposed to be connected to the liquid/vapor separator valve on the top/front of the fuel tank that connects to a steel fuel vapor line and the other end of said vapor line ends up connecting to the EVAP canister. The canister then uses a larger foil/paper hose that leads to the air cleaner housing, where the engine creates a slight vacuum that draws the fuel vapors into the engine itself. On the canister there is a plastic hood over its went to atmosphere. It is a very simple system that really works well to reduce fuel vapors from getting into the atmosphere.

You're exactly right on the evap system. If it's not connected to the air cleaner, then the engine cannot burn this vapour. This is what happens when people decide to add sporty non factory air cleaners unless that aftermarket one has a port in the base to receive the 3/4" foil/paper (if it's original) hose.
Having worked with air cleaner development for 35+ years, there's a reason why factory cleaners are made the way they are and the elements are tested to provide the correct restriction for a given engine.

 

[giantpune]

There are a number of joints in the fueling system where one component is supposed to seal with another one. Any one of them can fail and create a leak.
Something that may help narrow it down is the fuel level. Does your fuel level go down? Will it leak completely dry if you let it?

If you have a leak where liquid fuel can drip out, it may be evident by visibly moist areas, or areas that are cleaner than everything else around them.

About the lowest point in the system is the hole in the fuel tank where the sending unit goes into the tank. I have had the locking ring give out and I developed a leak at the sending unit. If given enough time, the tank will drain completely. Some fuel tanks even have a drain plug, which you should check.

From there, working towards the front of the car, there is a rubber hose that connects to a steel line running most of the length of the car. The hose may leak at either end and that steel line may rust out. Again, since these are low in the system, a leak here would allow most of the fuel to drain out.

That long line gets you up near the engine bay, with more transitions between rubber hose, steel line, fuel filters, the fuel pump, and the carb. The connections at the fuel pump are a common place to see a leak. And I have seen a leak at the fitting going into the carb, as well as the carb itself leaking internally.

Back to the fuel tank, the top of it has the big filler neck inside your trunk with a big rubber gasket. The fuel neck goes through your tail light panel and seals against that with a gasket. And then the gas cap seals against the fuel filler with yet another gasket. These are high enough in the system, you dont typically see liquid fuel leaking. It does help diagnose if you smell fuel inside the car, specifically inside the trunk, which then makes its way into the cabin.

Then the aforementioned evap setup with the steel line running back from the charcoal canister to a rubber hose and then into the top of your tank.

Something else that can lead to a "smells like gas" smell is an exhaust leak. Even a small one you can't even hear. An exhaust leak dumping out close to or in front of where you're sitting can make its way into the car.

 

[Stanglover]

Have you thought it might simply be running way too rich.
Not to say this is YOUR problem at all, but when I installed a new Holley Street Avenger 670 cfm carb, the smell of gas was enough to choke a horse in the garage. After I did all I could to lean it out without success, I took the car to a tuning specialist, who performed surgery on the primary plates by drilling a 3/32" hole in each butterfly. The result was no more over rich smell, the idle was far smoother, the transfer slots were where they should be, the AFR reading was now spot on and I'm still a happy camper.......... and so is the wife who complained about the smell getting into the house.
The point, check everything.

 

[mrgmhale]

I did not mention that the fuel pump be leaking if it has a leaking or ruptured diaphragm. When that happens is the pump will leak liquid fuel externally, internally, or both. An external leak will simply dump fuel all over the ground. If it is an internal leak it will let raw fuel get into the crankcase which dilutes the oil and inhibits it’s ability to properly lubricate the internally lubricated parts. In either case there is no need to do a Pressure and volume test.

If you pull the engine dipstick and dime the level is too high and/or the oil smells like gasoline you will need to replace the fuel pump, then change the oil and filter before driving anywhere.

Replacing the fuel pump is relatively easy. But are some tricks that make is easier. Plus I would suggest replacing any old rubber fuel lines at the tank sending unit, the fuel pump, and at the fuel filter.

I also have a YouTube video showing how to replace those fuel lines and fuel pump (of course). Once back at my laptop I will provide that link.

 

[Stanglover]

I did not mention that the fuel pump be leaking if it has a leaking or ruptured diaphragm. When that happens is the pump will leak liquid fuel externally, internally, or both. An external leak will simply dump fuel all over the ground. If it is an internal leak it will let raw fuel get into the crankcase which dilutes the oil and inhibits it’s ability to properly lubricate the internally lubricated parts. In either case there is no need to do a Pressure and volume test.

If you pull the engine dipstick and dime the level is too high and/or the oil smells like gasoline you will need to deplane the fuel pump, then change the oil and filter before driving anywhere.

Replacing the fuel pump is relatively easy. But are some tricks that make is easier. Plus I would suggest replacing any old rubber fuel lines at the tank sending unit, the fuel pump, and at the fuel filter.

I also have a YouTube video showing how to replace those fuel lines and fuel pump (of course). Once back at my laptop I will provide that link.

And don't forget, with Ethanol fuels these days, you'll need Fuel Injector grade rubber hose. A lot more expensive, but necessary.

 

[mrgmhale]

And don't forget, with Ethanol fuels these days, you'll need Fuel Injector grade rubber hose. A lot more expensive, but necessary.

Absolutely, and a good point. In our aarea (Rochester, NY) all the parts houses we have are using only the newer fuel lines that are resiliant with alcohol, and in fact have a higher pressure limit for fuel injection systems. They are playing it safe. YMMV. If you have a fuel injection ssytem always ask for the higher pressure capable fuel lines.

 

[mrgmhale]

I did not mention that the fuel pump be leaking if it has a leaking or ruptured diaphragm. When that happens is the pump will leak liquid fuel externally, internally, or both. An external leak will simply dump fuel all over the ground. If it is an internal leak it will let raw fuel get into the crankcase which dilutes the oil and inhibits it’s ability to properly lubricate the internally lubricated parts. In either case there is no need to do a Pressure and volume test.

If you pull the engine dipstick and dime the level is too high and/or the oil smells like gasoline you will need to replace the fuel pump, then change the oil and filter before driving anywhere.

Replacing the fuel pump is relatively easy. But are some tricks that make is easier. Plus I would suggest replacing any old rubber fuel lines at the tank sending unit, the fuel pump, and at the fuel filter.

I also have a YouTube video showing how to replace those fuel lines and fuel pump (of course). Once back at my laptop I will provide that link.

Okay, I am back home. The YouTube video I have re: replacing a fuel pump (on a 73 Mustang 302 2v) also includes how to replace the fuel tank fuel line, and the fuel pump fuel line. It sounds like it ought to be easy, and it is. But, it is tedious and there are some tips in the video that will save you potential grienf.

The video shoes how to replace a fuel pump on a 302 engine. The 351W engines are the same, but the 351C engine is a little different the mounting bolt pattern. Otherwise it is all the same. Other engines are also a little different, but the same techniques are used.

I actually split the task into three videos:

https://youtu.be/lkKVcliOd2w

https://youtu.be/Xp8vLVlxtVk

https://youtu.be/BmQpNEHPgaw

 

[Stanglover]

Absolutely, and a good point. In our aarea (Rochester, NY) all the parts houses we have are using only the newer fuel lines that are resiliant with alcohol, and in fact have a higher pressure limit for fuel injection systems. They are playing it safe. YMMV. If you have a fuel injection ssytem always ask for the higher pressure capable fuel lines.

And I'll add to that to make sure to use CORRECT fuel line clamps, NO FRIGGIN GEAR CLAMPS on fuel lines!

 

[sgtjd]

Thanks everyone for the concise answers! I discovered two issues; one was the evaporator hose missing which I'll get that replaced the other is I discovered exceedingly small drops of oil from the differential getting on the muffler pipes that caused a burn smell after being hot. I stopped that leak and cleaned up the muffler pipes. Now onto to the vapor hose.

 

[sgtjd]

I like the prior responses, but wanted to expand on the fuel evaporative control system (EVAP) a bit. The EVAP system is one of those rare emission control systems that actually does a lot of good, but it has no adverse side effects - at least when it is working properly. The biggest problems I see with EVAP systems is when folks, not understanding how it works, begin to disconnect hoses to the canister, or connect a vacuum line between the intake manifold and the EVAP charcoal canister. When the larger foil & paper vapor hose that connects the EVAP canister to the air cleaner housing is disconnected the canister gets loaded with fuel that is not sucked into the engine and burned. In severe cases so much fuel vapor os collected in the canister that is begins create liquid fuel which can start to small really strong.

I have attached some files that show how the EVAP system is supposed to be connected to the liquid/vapor separator valve on the top/front of the fuel tank that connects to a steel fuel vapor line and the other end of said vapor line ends up connecting to the EVAP canister. The canister then uses a larger foil/paper hose that leads to the air cleaner housing, where the engine creates a slight vacuum that draws the fuel vapors into the engine itself. On the canister there is a plastic hood over its went to atmosphere. It is a very simple system that really works well to reduce fuel vapors from getting into the atmosphere.

Can you send me a link to purchase the vapor hose and the connection that goes into the air cleaner? Most places I'm finding are out of stock.

 

[Stanglover]

Can you send me a link to purchase the vapor hose and the connection that goes into the air cleaner? Most places I'm finding are out of stock.

Maybe worth looking into. I got a 3 foot x 3/4" aluminum foil hose from NAPPA several years ago. I cut it in two, cleaned it and painted it with some textured spatter paint I had on hand, then I painted it with SEM Trim Black, my go-to paint for many projects., The result looks almost as good as the original paper/foil hose.
The elbow connector is very hard to find from what I hear. You'll also need one of these, orange arrow. These at least are easy to find anywhere.

 

[mrgmhale]

Can you send me a link to purchase the vapor hose and the connection that goes into the air cleaner? Most places I'm finding are out of stock.

Here re some links I found. I hope you find one!

https://www.mustangsetc.com/3-4-air-cleaner-to-charcoal-canister-fuel-vapor-hose/

https://secure.cougarpartscatalog.com/d1uz-9d667-a.html

They replace the following Ford Part #s:
D0AZ-9D667-A (which was later replaced by D4ZZ-9D667-A)

 

[mrgmhale]

Here is info on the plastic connectors for the Fuel Evap Vent Hose (3/4" I.D.), in the attached file.

 

[sgtjd]

Here re some links I found. I hope you find one!

https://www.mustangsetc.com/3-4-air-cleaner-to-charcoal-canister-fuel-vapor-hose/

https://secure.cougarpartscatalog.com/d1uz-9d667-a.html

They replace the following Ford Part #s:
D0AZ-9D667-A (which was later replaced by D4ZZ-9D667-A)

View attachment 76164

Perfect information

 

[Stanglover]

My bad on the "elbow" I mentioned. I meant the 3/4" straight connector obviously. But yes, those 90 degree elbows are hard to find new.

 

[mrgmhale]

My bad on the "elbow" I mentioned. I meant the 3/4" straight connector obviously. But yes, those 90 degree elbows are hard to find new.

It is so hard sometimes to find what the "latest" info is on some parts. It is like trying to hit a moving target without being to move ourselves at times. One would thing Googling for the latest info would make things easier, but too often now there is such an abundance of info... I guess that is part of what makes our hobby so interesting, and even fun. We never know what is going to happen as we turn rocks over to see what is underneath. heh heh