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Gas leak, occasional power loss

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JG2020

Gas leak, occasional power loss

I noticed on a couple of very hot days gas leaking from the top of the tank. I had this issue before when filling all the way and replaced the breather gasket on the top of the tank. I have not checked this again to see if that's the issue or maybe it's coming from the fuel take sender.

More concerning is I got on the highway and the truck started bogging down like I was running out of gas. Press the pedal to floor and it would just start to die. Then it would pickup speed again and then start to die again. My fuel gauge is broken and I thought for sure I was out of gas. It started running fine but I stopped at a gas station just to check and put in only 5 gallons to fill it.

This was about a 40 mile drive each way. It happened once or twice more on the way to the Dr. and back.

I took it out the other day for about 25 minute drive and same thing. Acts like it has no fuel. Then it kicks back in and is fine.

Any ideas? I thought I read the carb nuts might loosen on the 300? I have not checked yet as I have been away. I did a quick check after my last drive and did not see any vacuum hoses loose or anything obvious.

Thanks!
Josh

Josh G
1984 F-150 Inline-Six 300

Gary Lewis

Re: Gas leak, occasional power loss

Administrator

I think you may have a problem with the rollover valve. It sits in the top of the tank and if its grommet is cracked or shrunk it can leak when you get the tank completely full.

And if it is stuck partially shut, or if the vent hose is partially clogged, then you could be pulling a vacuum on the tank as you drive, which will prevent the fuel pump from keeping the carb full of gas. But I'm not quite sure why it would start working again, unless by bogging down that releases the vacuum?

Is this the front or rear tank? The top of the front tank can usually be reached from under the truck, although getting a good look at the valve and its grommet might be difficult. Perhaps with a camera? And check the vent hose that is connected to it. The hose must not be blocked.

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

Frank Wyatt

Re: Gas leak, occasional power loss

On the issue of losing power don't over-think things and do as my Grand-Dad always told me, check the simple things first. It's easier and almost always cheaper, like a clogged fuel filter. .i had the same issue and it was a clogged fuel filter, and it looked just fine but is was probably about 95% clogged.

1981 F 150 Custom 300 ci with a fully rebuilt 1968 240 head Carter YFA T-18 3.25 9" rear 2WD
dual gas tanks
1990 Lincoln Town Car 5.0 AOD
Home town Mc Kenzie, TN

JG2020

Re: Gas leak, occasional power loss

Thanks all,

I replaced the grommet and vent valve a few hundred miles ago because the truck was overflowing when I filled it up. That fixed that problem. .I will have to take a look and see if something happened to it.

This leak happened while just sitting and the tank was about 2/3 full. It was really pouring out down the side of the tank onto the street. A steady stream.

The fuel filter has about 500 miles on it but easy enough to change I guess. This is the side tank. I did buy one of those flexi cameras when I was troubleshooting the vent valve grommet so I can take a looksy.

I need to really drop the tank down enough replace the fuel gauge sender also. Raining here today so I will report back tomorrow!

Josh

Josh G
1984 F-150 Inline-Six 300

Gary Lewis

Re: Gas leak, occasional power loss

Administrator

If it truly was only 2/3 full and you had that kind of a leak then I'm at a loss as to what could do that. But gas expands quite a bit and I've had leaks with my trucks if I fill the tank up FULL and either drive it or sit it outside. Driving it seems to heat the tank from the exhaust and if it is the tank that is not being used it can overflow. But I wouldn't expect a tank that was only 2/3 full to have that problem.

When you are looking for things, check out the vent hose. One of mine was off and it was leaking there as the outlet of the rollover valve is well below the filler neck.

Gary, AKA "Gary fellow": Profile

JG2020

Re: Gas leak, occasional power loss

Update! I was away for 9 days and when I went to start old Bessy up she would not have it. This truck has always started right up. Tried for 10 mins . Choke is operating normally. I ended up having to spray some gum out and after a couple tries got her running.

The carb mounting bolts had about a turn and a half or so on each one so I tightened those. 2 vacuum caps on the tree were dry rotted and broke apart when I pulled on them . I replaced all the caps and also recut the brake booster house and clamped since the end was bloated and had some cracks.

This morning the truck started right up and was purring like a kitten. It had been running a little rougher lately.

Drove to the supermarket and got about a mile from and lost power. Was bucking all over the place. Not fun on a bridge ha ha. I made it into a parking lot and the truck was idling perfectly . Gave it gas in neutral and no bogging down. Choke was wide open. It happened a couple more times but I made it to the market.

On the way back it happened once . Totally just bogged down like it had no fuel. Pumped it in neutral and it came back and made it home fine. It doesn’t seem like it’s related to giving it more or less gas pedal. I’ll be crawling under with the camera to see what I can see.

Sorry for the long story!

Josh G
1984 F-150 Inline-Six 300

JG2020

Re: Gas leak, occasional power loss

Happy 4th to all by the way! I took some pics. Found the fuel filler hose cracked some and not secured. Fixed that. I have a new one to replace with. The rollover vent valve I replaced with the new gasket attaches to this metal line in the photo. It was tucked into the frame up from and goes nowhere .

Since my fuel gauge is not working ( goes 1/2 way when full and then drops to empty after about 20 miles I may as well drop the tank and replace all those bits .

Josh G
1984 F-150 Inline-Six 300

Gary Lewis

Re: Gas leak, occasional power loss

Administrator

Also check your fuel lines. The rubber hoses from the tank to the hard line, and from the hard line to the fuel pump. And from the hard line to the switching valve and back to the hard line if you have dual tanks.

The hoses can get so bad that they allow air in, which kills the pump's ability to move gas to the carb. I've had a truck die on me repeatedly until I replaced the hoses.

Gary, AKA "Gary fellow": Profile

JG2020

Re: Gas leak, occasional power loss

Thanks Gary! I am going to order it all from LMC and get this done . Hopefully that fixes the issue. I’ll replace the fuel filter also for good measure even though it’s new .

Josh G
1984 F-150 Inline-Six 300

JG2020

Re: Gas leak, occasional power loss

The metal line that goes all the way from the vent valve on top of the tank to nowhere at the front of the truck....

I assume this used to go to a long gone charcoal canister of some type? Can I just eliminate most of it and just leave a small vent tube?

Thanks

Josh G
1984 F-150 Inline-Six 300

ArdWrknTrk

Re: Gas leak, occasional power loss

Administrator

The charcoal canister would probably be on the frame rail behind the battery.
You can leave it off but will likely get a whiff of fumes in warm weather.
If you park inside the garage will stink.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

grumpin

Re: Gas leak, occasional power loss

Mine did as Jim said, would smell of gas when parked. I had my charcoal canisters still.

One canister is still on the truck with that line going to it then up to the carb. No more smell.

Might be able to find one at a junkyard.

Dane
1986 F250HD SC XLT Lariat 4x4 460 C6-Sold
1992 Bronco XLT 4x4 351W E4OD
1998 GMC Sierra SLE K1500 350 4L60E
Arizona

JG2020

Re: Gas leak, occasional power loss

In reply to this post by Gary Lewis

I am thinking Gary wins the prize ! The truck finally got to the point where it would not start. I replaced the fuel filter , no go. Fuel pump , no go. Pulled the fuel line from the sensing unit it to the metal fuel line and it looks pretty bad. If I hold my finger on one end and blow air comes out of the small perforated looking holes . Off to get some fuel line!

Thanks again everyone,

Josh

Josh G
1984 F-150 Inline-Six 300

Gary Lewis

Re: Gas leak, occasional power loss

Administrator

Been there, done that, several times. Which is why I think of it in these situations. Glad you found it.

Gary, AKA "Gary fellow": Profile

JG2020

Re: Gas leak, occasional power loss

Thought I posted this but I guess not. I’ll replace the fuel hose tomorrow. I have been thinking about driving the truck to the Adirondacks about 300 miles. Can’t see why it wouldn’t make it ? I’ll change the gear oil and tie rod ends first . I got a new sending unit also which will hopefully fix the fuel gauge.

Josh G
1984 F-150 Inline-Six 300

Gary Lewis

Re: Gas leak, occasional power loss

Administrator

I hope you got ethanol compatible hose. Not all hose is. I have a picture somewhere of what I buy at O'Reilly's, but I can't find it. Anyway, it says on it that it is compatible.

With a few changes and checks I'd think your truck would be able to make 300 miles.

Gary, AKA "Gary fellow": Profile

JG2020

Re: Gas leak, occasional power loss

Will look for that at autozone . I would think if it can do 100 miles it should do 300. I’d prob bring spare belts, alternator , water pump etc. I took a vw bus from NJ to key west and back when I was younger and more foolish. I brought new heads , brakes , carbs , belts and whatever else I could think of with me. If it started back then I drove it!

I think anything major on the truck that was wrong would rear it’s ugly head with some warning . No gears slipping , no smoke etc.

Josh G
1984 F-150 Inline-Six 300

Gary Lewis

Re: Gas leak, occasional power loss

Administrator

In '69 Janey and I drove a 50's VW van on vacation for several hundred miles. No spares, no nothing. The alternator light came on about halfway through the trip, but since we didn't use any lights as we were driving in the daytime I didn't worry about it. And we made it home.

Anyway, if your truck is making 100 mile trips it'll probably make 300 miles. But, good luck!

Gary, AKA "Gary fellow": Profile

JG2020

Re: Gas leak, occasional power loss

Those VW days were some fun times ! No more power loss issues since replacing the hose. I replaced all the rubber hoses and the fuel pump for good measure. The truck is running “ok” . The exhaust smells some and I have some smoke while idling. Not a blue but more a grayish color. Pulled the plugs and they don’t look great. Any opinions appreciated ! Idle mixture is set about 1.5 turns out but before the power loss I had set it by vacuum gauge . The carb was an old carter that was rebuilt and sitting on a shelf for a long time before I bought it on eBay. Haven’t touched it except for adding the electric choke which works properly and the idle mixture screw.

Spark plugs are in order from front of truck towards the windshield .

Thanks as always !
Josh

Josh G
1984 F-150 Inline-Six 300

Machspeed

Re: Gas leak, occasional power loss

Administrator

This is a great story and one that benefits all of us as we work to fix and restore these old trucks. Glad you got it fixed and thanks for following up on the fix, Josh.

John

"Blackie" - 1986 F150 4x4 - Mildly warmed over 351W HO - Original owner

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