Hey guys, got a little bit of a problem with my 86 F250 w/460.

If the truck sits for any longer than a day usually, pretty much all of the fuel will drain out of the carb, and run back into the tank.

Last weekend, I discovered that my factory original fuel filter was leaking in front of the carb, and then the leak was blowing all over my intake manifold and causing not only a huge mess, but also a potential fire hazard.

I called LMC, and Ford, and found that they no longer make the fuel filter like that. I also kinked the original steel line so I decided to drastically simplify everything and replace the line with rubber hose, and a Wix plastic, see-through fuel filter.

Now, we can see immediately after you shut the truck off, the fuel runs out of the filter and back down the line. Then when you go to start the truck again after having sat for a day or so, I have to sit there and crank on it for damn near a minute before I get even a slight cough out of the engine!!

I was told by a friend that I should invest in a "lift pump". I guess these are primarily used for diesels and racers alike that need extra fuel pressure during certain times. I on the other-hand only need it when starting. It's gotten so bad that i've considered keeping a small water bottle full of gas to pour in the carb before I start it every time, just so I don't have to sit there and crank on it for so long.

Does anyone know of any other way to prevent the fuel from draining out and having to invest in a $100+ lift pump? If I do have to go that way, i'll need to tap into ignition and have it so it runs when the key is turned on like a normal fuel injected vehicle. So I will need a diagram and know which wire does what and where it is.

The other question I have is, where would I even put such a thing? I do have dual tanks with electric fuel pumps in the tanks, i'm in the process of replacing my front tank with a new plastic one, and if I install a lift pump, it would need to work with both tanks, not just one. I wouldn't want to have my rear tank be my starting tank and my front tank be my driving tank, that'd be silly.

Thanks

 

What you describe is confusing to me. Not saying it's not happening, just confusing...


Are you running a stock 4180 or something else?


I've got an electric fuel pump on my 460 and the stock 4180 carb and I can't imagine it siphoning all the gas back out of the carb through the inlet valve. Just not physically possible.


Now what has happened to me is a leak down low on the front fuel bowl that allowed the gas in the front fuel bowl to leak away (in my case it was one of the lower fuel bowl mounting bolts, but leaks around the accelerator pump housing are also very common). Then I had to crank it long enough to refill the fuel bowl before the thing would start...from what you describe I'd be looking closely for a fuel leak around your front fuel bowl.


Also there should be a fuel pump bypass wire attached to the small "I" terminal of your starter relay. The purpose of this wire is to energize the fuel pump while cranking. The wire is a fusible link and if its burned out your fuel pump won't pump no fuel while you be cranking...


If you want a method to prime your carb before you crank you can run a jumper wire from the hot post of your battery to the fuel pump bypass wire and you should hear the fuel pump operate. Just don't leave the bypass wire hot for very long, since it's feeding a full 12v to the pump you could burn some wiring that way.


Just be extremely careful if you do jump the fuel pump bypass wire...the other small terminal (S) on your starter relay (solenoid) is the starter signal wire, and it you jump to that terminal accidently the starter will engage...and you don't want to be standing in front of your truck...with it in gear...and have the starter engage. That could be fatal.

 

Yeah, it is the stock Holley carb. Probably the 4180, but it is the original one.

It has been rebuilt, and my friend who did it knows his stuff about them. Basically the truck last ran in 2004 from what I can tell, and that was also the last time it was plated. The primaries looked like this when he took it apart:













The primary was completely gunked up and not functioning at all. The truck only ran on the secondary when I bought it. The clean bowl you see there was the back bowl, i.e. secondary. So it has been rebuilt and is now running like a champ. But today he took a look at it once he shut it off and watched the gas drain out of the clear filter. Then he told me about the lift pump, but didn't think about checking the accelerator pump. I can't see any new gas on the intake so I'm gonna guess it's not leaking, unless it leaks out of the carb into the motor, but it doesn't make sense that it would be returning to the tank. My dad said my fuel pump is losing its prime,but would that explain the fuel leaking back to the tank?

 

Yes that is a 4180 carb.


Without question, the nasty, gunky side was the secondary side and the clean side was the primary side. That's what happens with these carbs when you never get into the secondaries. The gas (especially now that it has ethanol in it) just sits in the secondary bowl and goes sour.


Also consider this: see the bottom of the inlet valve where it contacts the float? that's where the gas comes into the fuel bowl. No way it can siphon back out any lower than the bottom of the inlet valve.


Next things to check: Accelerator pump circuit. Remove the top of the air cleaner and pump the throttle. You should see a stream of gas shoot out of the squirter (accelerator pump nozzle). When my rig has sat for a while I usually need to give it 3 pumps of the accelerator before cranking. With those three squirts of gas it usually fires right up.


The other thing to check is the choke. When it's cold take the top off the air cleaner and pump the throttle. The choke butterfly plate on the top of the front air horn should snap shut. If it remains open you'll certainly have trouble with cold starts.

 

If fuel is running back out of the fuel line going to the carburetor it shouldn't affect starting unless the bowls dry up by evaporation or leaks, as Brnfree points out.

Edit my own stupidity for not clearly reading the last paragraph of the OP.

The pumps should run while the starter is engaged.
Check the blue fusible link connected to the 'I' terminal or the starter cable lug of the solenoid.

 

Since you have electric pumps already, adding another one isnt going to gain you anything you can't do with the existing one.
Like mentioned you can manually power up the pump and see if that fixes your problem.
I have never had a drainback issue with my truck, I would be more inclined to think you have a leak in the system somewhere on the engine side of the selector switch or internally in the switch if it does this on both tanks.

 

When you talk about the accelerator pump, do you mean this?




Because I recall that looking a little shiny from before, but didn't think much of it because it wasn't leaving a pool on the intake. Thought it might be a sealant or something.

I need help with labeling which part is the butterfly choke. Do you have a picture you can reference?

Now that I think about it, the problem has to be with one of the bowls leaking down. Because the gas SHOULD stay in the carb even after turning it off. Am I right? The primary should hold the gas until it is next needed. That's why the primary was so nasty and gunked up when I bought the truck because it sat for 10 years with gas in it and was never used.

I watched it last night after turning it off and saw the gas drain out of the line. Does that mean it's draining out of the carb and back into the line from the primary, or is it draining into the motor? The carb was just rebuilt by my friend, so any work he guarantees. What should I tell him to look at? I'd like to kind of give him an idea of what to look for before we start tearing everything apart.

 

Yes, that is the acellerator pump.
DO NOT OVERTIGHTEN IT!
The cover is already prone to warping and causing leaks.

The choke butterfly is the flap visible at the front top of the carb.
The list and build numbers are stamped on the front of the choke horn.

 

No gas can drain back down the fuel line from the float bowl.
There is no way to start a siphon when there is an air gap between the float level and the float valve itself.

 

Tell your friend the carb is not holding fuel and ask him to go through it again paying close attention to the pump cover.
Check it against a known flat surface and use tiny taps from a 4oz ball peen hammer to correct it if you can see light.
(I use a small granite surface plate)

For God's sake use the correct Holley 3-1346 gasket kit.
Aftermarket kits cause more problems than they fix.

 

With that accelerator pump gasket...is it something that I can check, or does the whole carb need to be taken apart again? Does Holley make JUST that gasket, or does it require the entire kit just to get the one that I need?

 

You can get just the diaphgram.
You need one for a 30cc pump, not a 50.

 

I tried doing an amazon search and came up with the whole kit.

Do you have any links to where I could get just the accelerator pump gasket? Or do I need to visit my auto parts store?

Thanks, you guys have been a tremendous help!!

 

You need to go to Holley or a performance store.
I'm sure the LAP could order one for you but unless they are into musclecars its likely they're just going to order from Holley.

 

135-5 just the part.
135-12 with 4 cover screws.

You don't need to disassemble the carb, but you need to remove it and flip it over.
Lots of fuel will spill out the 'straws' on top.
Check the cover for flat and check arm gap of .015" when you reassemble, and connect the throttle cable.