How to find a Fuel leak?

[jv982]

'90 Ranger 4.0L 2wd

When it is cold outside (under 45F) my truck has a fuel leak that smells really strong. I noticed it last winter, but once the weather warmed up it completely went away. Never smelled it once. Now that it has gotten a little more chilly the smell is back. Also, when I try to start the truck in the morning, I have to crank the truck longer then normal for it to fire up. My guess is that the colder temps cause some crack to get a little bigger and air gets into the lines. The leak does not seem to be so big to be causing any drop in MPG. It is just big enough to make me dizzy on my way to work

The problem with all of this is that I have tried to find a leak but have not seen any. I guess I really don't know where I should be looking, and the easiest way to try and find it.

 

[289-tiger-]

If you have a leak from the pressure end of the pump it will be pretty easy to find. The evap canister or vaccum lines to the purge could have a leak, on 94's the fuel filler neck cracks at the base causing a mess at fill ups, have seen steel return lines on Explorers pumps rust out. Chase the problem seriously... cabin fires are a bitch.

Good luck

 

[jv982]

Thanks for the reply... I think that it is on the pressure side because of the extended cranking required in the mornings, but I have not been able to find any leaks. Are there any specific places that I should be looking at? I wouldn't think that vacuum leaks would cause air to get into the lines. Is that correct? What do you mean the purge?


Its funny you mentioned the fuel filler neck. Mine developed severe cracks and I replaced it recently.

 

[JeepRecoveryTeam]

i have the same problem tried to drop the gas tank to see if there was a leak in the line or something but couldnt drop the tank, i have to pull the bed off to see whats up. good thing gas prices are going down

 

[289-tiger-]

Thanks for the reply... I think that it is on the pressure side because of the extended cranking required in the mornings, but I have not been able to find any leaks. Are there any specific places that I should be looking at? I wouldn't think that vacuum leaks would cause air to get into the lines. Is that correct? What do you mean the purge?


Its funny you mentioned the fuel filler neck. Mine developed severe cracks and I replaced it recently.

Sorry for not being clear. There should be 3 lines running back to the tank along the driver frame rail (pressure to regulator from pump, return and vent lines.) Can't speak for the 90 but the 94 the vent from tank will go to the carbon canister which could develop cracks giving you the fuel smell maybe. The canister will have a vacuum line to a purge selenoid and will reduce to a 1/8" vacuum line entering the driver side of the throttle body(the rubber lines should be inspected also.). There is also a steel connection line on the vent line behind the fuel filter in the frame that could rust. I can only suspect that you are smelling the fumes from a non pressure connection because you have not actually found a dripping leak. As said treat it seriously and just walk through the system. No smoking, it's the fumes that are bad around sparks.

Good luck

 

[jv982]

Thanks for the specifics. I appreciate it.

The only thing is that I think it is on the pressure side. The truck does require extended cranking when I am starting it on a cold morning like there is air in the lines.

 

[Bryan22]

I would check the fuel filter on the frame rail when was the last time you changed it? metal expands with heat and contracts with cold.... the fuel filter is metal, maybe that's why it only does it in cold weather. If it's been a while it needs to be changed anyways, for 10 bux you can't go wrong.

 

[289-tiger-]

Thanks for the specifics. I appreciate it.

The only thing is that I think it is on the pressure side. The truck does require extended cranking when I am starting it on a cold morning like there is air in the lines.

No problem, If you suspect the pressure side check or have checked fuel pressure at the manifold rail. Low pressure from the pump could cause the cranking issue. If pressure holds KOEO after it primes your system should be tight to the rail. Vacuum leaks off the evap side or at manifold could also cause the cranking issue on the intake side. Run the fuel system from the gas cap to the injectors to see where you are smelling the gas fumes.

Also check the vacuum line at the regulator for any fuel leakage.

Good luck

 

[jv982]

Thanks for all of the great advise. Unfortunately I was planning on troubleshooting this today, but there was no leak today. No fumes, no smell. Troubleshooting intermittent problems sucks!\

I purchased a fuel filter, but I don't want to replace it unless it is leaking there. I don't want to introduce any possible new problems until this is figured out.

 

[Bryan22]

a new fuel filter wont introduce a new problem, just put it in and run it. If you don't smell the fuel anymore than you won't have to keep messing with it. They're super easy to change if your's is mounted in the same place as my 3.0 and 2.3 are. and if you're worried about it stuff an o-ring in on each side of the filter to make sure it seals.

 

[289-tiger-]

a new fuel filter wont introduce a new problem, just put it in and run it. If you don't smell the fuel anymore than you won't have to keep messing with it. They're super easy to change if your's is mounted in the same place as my 3.0 and 2.3 are. and if you're worried about it stuff an o-ring in on each side of the filter to make sure it seals.

Never "stuff" anything into a pressurized fuel line that was not designed by the manufacturer of the fuel system (stock or modified). Especially, if it is near a heat source.

 

[Big Jim M]

Oh yeah!

a new fuel filter wont introduce a new problem, just put it in and run it. If you don't smell the fuel anymore than you won't have to keep messing with it. They're super easy to change if your's is mounted in the same place as my 3.0 and 2.3 are. and if you're worried about it stuff an o-ring in on each side of the filter to make sure it seals.

An "extra" o-ring will only cause LESS pressure on the rings which in turn might CAUSE a leak! Just use what comes on the new filter and forget about re engineering the gaskets.
Big JIm

What I'd try first is to go out on a cold morning and turn the key to the RUN position which will energise the fuel pressure...I would leave the key in that position and inspect from stem to stern..if while looking the pump came back on it would be an answer to the question of wheather or not there was a leak.
Big Jim

 

[JohnPi]

Come on! All these replies and nobody answered the question on how to find a fuel leak with "Light a Match!"?

 

[Mutant Pony]

The fuel lines rust off the top of the sender frequently. That doesn't correspond with temp change though. The charcoal canister is more likely to smell on a HOT day as well. The only thing I can think of is an o-ring.
I had an injector upper o-ring leaking on the wifes caravan. That was very difficult to find and very dangerous to drive. I eventually found it by the stain, gas leaves a unique pattern. You are basically looking for a clean spot with a faint, white outline.

 

[Bryan22]

Never "stuff" anything into a pressurized fuel line that was not designed by the manufacturer of the fuel system (stock or modified). Especially, if it is near a heat source.

first of all the only thing holding those lines on is a plastic clip, and second name one heat source remotely close to the fuel filter. I had an old on that leaked and a little o-ring sure as shit did solve the problem. and I said replace it to begin with. look on this site and you'll see alot of people who've had a 10 dollar fuel filter be the problem. Alothough "stuff" probably was bad wording. haha. I "slid" one on the filter till it hit the hump.