mysterious fuel leak

[Kremer5]

Hello Bronco team,

I had a strange experience last week and I am still scratching my head. I was driving around on my lunch break and smelled a strong gasoline odor. Parked the rig at work. it looked like fuel was dripping down the left side of the motor, it was hitting the front axle where the PS radius arm attaches. It also looked like a smaller drip on the drivers side but I didn't touch/smell the fluid to confirm

Went inside and grabbed a retired mechanic and we couldnt find the source. Drove it around and could only smell gas, but no leaks.

Any thoughts?

 

[DirtDonk]

You could see gas, so you know the area. Sounds like you'll just have to keep digging (maybe very carefully, while the engine is running?) in that area to find the source.

Basically though, the entire fuel line and pump are on the left/driver's side of the vehicle. So it's hard to diagnose from afar.
If things are stock-ish, your fuel line runs up the inside of the left frame rail, to the selector valve (if you have two tanks?), then up the frame rail to about the engine mount tower, where it transitions to the top of the frame rail and then on over to the pump mounted to the side of the engine.
Even the hard line from the pump to the carburetor could show as a leak on the driver's side, because liquid fuel can travel in some mysterious ways along some pretty awkward edges before it drops down on to the axle.

The stock fuel lines in that area are plastic until the pump, then metal after that. While they're extremely reliable, any of them can develop a leak. Especially at joints or rubber hose areas where junctions are.
An old fuel pump is high on the list of leaky culprits too. Especially if it's been sitting for extended periods between very little driving time.
Where are you located? How much ethanol is in your gas? Or whatever it is these days that everyone seems to think causes more harm than good? Apparently pump diaphragms don't like some of the new chemistry.

If a diaphragm leaks it can pump gas into the crankcase. So best check your oil level just in case. If it's higher than normal you might have gas going inside and you'll need to drain it.
They can also leak out of the vent hole, which will spray gas in various nooks and crannies but not always show a visible active drip.

Good luck.

Paul

 

[B RON CO]

Hi, you don't say if you have FI or stock. Assuming stock, as mentioned, go over the line from the left chassis, to the pump, to the carb. It goes from steel tubing to rubber a couple of times, and maybe add in a filter. I would go over that and jiggle it when it is running. I would probably change all the rubber hoses and filters now. Leaking fuel is serious. Don't put the job off. Good luck

 

[Rustytruck]

The line from the tank to the fuel pump is gravity fed and under vacuum when the engine is running so fuel isnt supposed to leak out with no pressure. check all hoses and hose clamps. If you fuel line and vent system is compromised there is a possibility to build pressure in the line if its hot out and your vent system isnt working properly. Check the cap and your vent lines up into the condensing bottle behind the drivers seat if you have a later model. If you have a side tank check around the sending unit area. i had a friends Bronco where someone put in a carpet kit and drove screws down into the side tank. Never know what these Broncos have gone through with previous owner in 40-50 years.

 

[ledslinger29]

Run your finger around the bottom of the fuel pump after you drive it. My pump gaskets were leaking badly


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[Quick & Dirty]

I've had accelerator pumps leak onto the intake manifold.

 

[Kremer5]

Thanks everyone for the advice. I'll spend some time this weekend going through your suggestions. This rig was recently restored by me although the motor hasn't seen too much work and has spent most of its life turned off.


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[Kremer5]

Thanks everyone for the advice. I'll spend some time this weekend going through your suggestions. This rig was recently restored by me although the motor hasn't seen too much work and has spent most of its life turned off.



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[Kremer5]

It came back. Fuel pump weep hole. Thanks for the advice


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[B RON CO]

Hi, check your oil. Fuel may have gotten into the crankcase through the faulty fuel pump. If your oil level is high or the dipstick smells like gas change the oil. Good luck

 

[Kremer5]

Thanks for the advice I'll keep that in mind for next time. I did an oil change while I was under the hood


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