1978 FJ40 2F Carburetor return line flow questions. (1 Viewer)

[Helimancan]

It's all good !

Until I can get my hands on it I won't be able to report back with my success or failures

 

[65swb45]

So given that the carburetor is a 78, it’s theoretically possible to just hook up an M12 connection to the carb using a copper O-ring (headed to the fuel tank) and call it a day? That is, without any restrictor?

My particular carburetor is missing all of this stuff, so I can't examine. I wasn’t sure if the bolt going through the banjo was a particular length, or a particular flare at the end that served to restrict fuel flow.

Sorry if I’m hijacking – I assumed I wasn’t because we appear to have a similar issue.

Across the valve cover?

The whole point of having dedicated fittings is to keep from stripping the threads on the carburetor air horn. @HKforte is looking at this as a possible issue on his ‘78 right now.

 

[thebigredrocker]

@65swb45 did you notice this?

Discovered that my fuel feed is connected to the banjo style fitting.

My return hose has been connected to the other union style fitting which is facing forward.

If this is right it means my lines have been swapped. It has been like this as long as I have owned the Toyota.

 

[65swb45]

@65swb45 did you notice this?

Yes.

 

[FJ40Jim]

Terminology is important.

The OP has a 2F carburetor, somewhere around 1978.

That carb is equipped with a fuel inlet fitting, no restrictor, 13x1.5 compression fitting outside, 12x1.25 w/ crushwasher into the carb.

There is a return system. It consists of a banjo bolt and a banjo fitting. The banjo bolt contains a brass restrictor (jet), and behind that is a rubber check valve/pressure regulator. The restrictor limits maximum fuel return flow. The rubber check valve has a cracking pressure, to maintain a minimum pressure in the fuel inlet of the carb.
The banjo bolt is 12x1.25 with crushwashers, the banjo fitting is 13x1.5 compression.

If fuel is attempted to be shoved into the return fitting, first it has to turn the rubber lips of the little check valve backwards, then it has to squeeze through the restrictor. It can be done, but doesn't work well, especially at higher loads, as the OP has discovered.

HTH

 

[Helimancan]

Good News !! Finally Swapped my fuel feed line and return line this past weekend. reset the carb float height as per the service manual and it is running like a well tuned Toyota tractor again !!

 

[chuckost]

The picture @thebigredrocker posted for the VERTICAL banjo bolt is the 73-74 type, which DOES have a restrictor. The 75-78 HORIZONTAL banjo bolt does not have a restrictor.

SOOOOOO, if you want to try adding a restrictor into your return line, then you would need the earlier style bolt. Problem is, I've never tried to see if that bolt would fit in a 2F carb. It seems like a bandaid, and I don't advocate bandaids.

Fuel, like water, will take the path of least resistance. Logic says that if the hole in the needle and seat were insufficient, marginally increasing the size of that fitting would make it easier for the fuel to go INTO the carburetor than the return line, without the need to put a restriction in the return line.

That said, considering hundreds of thousands of engines and carburetors are out there running around without this modification, it is far more likely that the fuel delivery is inadequate, rather than the size of the opening in the seat.

I did open up a needle/seat assembly once, AFTER determining that fuel delivery was adequate. And it did solve the problem on that vehicle.

Cheers.

My 1978 california has a one way valve and restricted inside banjo fitting!

 

[Stexag]

The OP has a 2F carburetor, somewhere around 1978.

That carb is equipped with a fuel inlet fitting, no restrictor, 13x1.5 compression fitting outside, 12x1.25 w/ crushwasher into the carb.

There is a return system. It consists of a banjo bolt and a banjo fitting. The banjo bolt contains a brass restrictor (jet), and behind that is a rubber check valve/pressure regulator. The restrictor limits maximum fuel return flow. The rubber check valve has a cracking pressure, to maintain a minimum pressure in the fuel inlet of the carb.

I have such carb with this bolt that I am installing on my '78 (replacing Holley that was there when I bought it). I'm pumping fuel but not filling the bowl. I pulled that banjo bolt and it does have a restrictor device in there, but I can blow through with no resistance. I am presuming the check valve 'cracking pressure' mechanism has failed.

I searched the parts book and came up with 21814-61021 but it looks like that part is discontinued? What is the recommended fix in this situation? Go to 3 line pump?

 

[65swb45]

I have such carb with this bolt that I am installing on my '78 (replacing Holley that was there when I bought it). I'm pumping fuel but not filling the bowl. I pulled that banjo bolt and it does have a restrictor device in there, but I can blow through with no resistance. I am presuming the check valve 'cracking pressure' mechanism has failed.

I searched the parts book and came up with 21814-61021 but it looks like that part is discontinued? What is the recommended fix in this situation? Go to 3 line pump?

You’re pumping through the return line?

 

[Stexag]

You’re pumping through the return line?

No sir. I'm pumping through the delivery line. However, the return line banjo bolt/check valve is not providing the designed resistance; so I am just circulating gas through the return and the fuel pressure is not overcoming the needle plunger spring to put fuel into the bowl.

At least this is my interpretation of what is happening based on Jim's quote above that the banjo bolt apparatus in my return should serve as a check valve. My pump is confirmed pumping fuel, it is running out the return - but the bowl is not filling. I can not find a resistance in the return system to build fuel pressure.

 

[65swb45]

No sir. I'm pumping through the delivery line. However, the return line banjo bolt/check valve is not providing the designed resistance; so I am just circulating gas through the return and the fuel pressure is not overcoming the needle plunger spring to put fuel into the bowl.

At least this is my interpretation of what is happening based on Jim's quote above that the banjo bolt apparatus in my return should serve as a check valve. My pump is confirmed pumping fuel, it is running out the return - but the bowl is not filling. I can not find a resistance in the return system to build fuel pressure.

Ah.

Every once in a while, I’ve seen where the needle’s rubber tip softens and gets stuck in the seat, blocking fuel flow into the carb. Not often, maybe six times in 1400+ carbs. But it happens. Considering how many carbs have them, I’m thinking that those few carbs got subjected to a particular fuel blend that softened them.
With the pre-75 carbs, it was/is a simple matter to pull the access plug above the seat and poke a paper clip through to the needle. With the 2F, you could try tapping on the carb since there’s no direct access.
But if you already know you have a rubber tipped needle, might as well hunt up a solid metal one and just plan on changing it out…and rechecking your float level while you’re in there.

When all is as it should be, the restrictor does it’s job just fine.

When I rebuild/setup a desmogged carb of that vintage for someone going back to stock, I put a solid bolt in and eliminate the banjo from the equation. Pre-73 carbs had no return, and they all do just fine without one.

 

[Stexag]

When I rebuild/setup a desmogged carb of that vintage for someone going back to stock, I put a solid bolt in and eliminate the banjo from the equation. Pre-73 carbs had no return, and they all do just fine without one.

Thank you so much for the advice. This last sentence tells me what I think I need to know. My carb is recently rebuilt and it has a metal needle. I have tapped, beat, and otherwise done every trick I know to free a stuck needle; but the needle isn't stuck. That's when I started investigating what was in the return system to regulate fuel flow - and eventually brought me to this thread.

As soon as I can find the darn hairpin that shot out of my needle nose pliers I am going to do just as you suggested and do away with the return. If I do that should I use a different fuel pump or will my pump self regulate the fuel pressure? I do not have a 3 line pump, mine is inlet and outlet only.

Thank you for the advice.

 

[Pighead]

might as well hunt up a solid metal one and just plan on changing it out…and rechecking your float level while you’re in there.

Just yesterday, coincidentally enough, my Pig didn't start on the first try. Odd. There was no fuel visible in the porthole, which explained that. I could get it to start if i filled the bowl via the vent, but it died when that emptied. I could get fuel to come out the return if i cranked the engine, so i took the top off the carb. Rubber tipped needle valve seemed stuck, so i searched for a metal tipped one. Picked the nicest one, polished it up a bit and put it in. Adjusted float level naturally. Drove around just fine after that.
I like the fuel return line.

 

[65swb45]

Thank you so much for the advice. This last sentence tells me what I think I need to know. My carb is recently rebuilt and it has a metal needle. I have tapped, beat, and otherwise done every trick I know to free a stuck needle; but the needle isn't stuck. That's when I started investigating what was in the return system to regulate fuel flow - and eventually brought me to this thread.

As soon as I can find the darn hairpin that shot out of my needle nose pliers I am going to do just as you suggested and do away with the return. If I do that should I use a different fuel pump or will my pump self regulate the fuel pressure? I do not have a 3 line pump, mine is inlet and outlet only.

Thank you for the advice.

Mechanical or electric?

 

[Stexag]

Mechanical.

I just put the carb back on and took some vice grips and pinched the return line fully closed. I started and ran the engine on a water bottle spraying fuel into the top of the carb. There is STILL no fuel in the bowl. I am puzzled; all new needle valve assembly but it still acts like it has a stuck needle. I'm going to pull it back off and give all of that another close look....

 

[Pighead]

still acts like it has a stuck needle.

Well, treat it like a stuck needle valve then. Take it apart, clean it out, put it back together. You say you're sure your needle valve is all metal?

 

[Stexag]

Well, treat it like a stuck needle valve then. Take it apart, clean it out, put it back together. You say you're sure your needle valve is all metal?

Yes, I had it apart yesterday and again this morning. It has an all metal needle valve with a spring and a plunger in it.

When I put the needle in and blow through it I can blow past the needle, but when I put the spring and plunger inside the needle and then the float... no way, in ANY orientation. How much residual pressure does that spring/plunger put on the needle? because it seems like it would take an unusually large amount of fuel pressure to overcome it. More than 3-4 lbs.

 

[Stexag]

Well, treat it like a stuck needle valve then. Take it apart, clean it out, put it back together. You say you're sure your needle valve is all metal?

I wanted to take the time to provide the resolution of my problem for anyone who may encounter the same. I'm quoting Pighead here for correctly pointing out that I was hearing hoofbeats and assuming giraffes.

I could not get fuel in the bowl even though the needle was was not stuck. As I pointed out in the post above, the needle was free, but with the spring and plunger in the needle the pressure open the valve was just not there. Bending the tab on the float to achieve FSM clearance made the geometry of the float tab way off (because the plunger was so proud out of the needle) and unnatural. To be sure I was up to spec I ordered a new fuel pump to eliminate performance issues there - That did not change anything.

After much trial and error with different float settings and talking to a friend I decided to trim the spring under the plunger. I arbitrarily started with 2 coils off the spring. Before trimming, at least 3/4 of the plunger protruded from the needle at rest. Cutting 2 coils left the plunger maybe 1/2 in 1/2 out. This did the trick. That little bit of relief let me set the float and on first start up - runs like a top.

Not a return problem - as I originally suspected that brought me here. Not a traditional 'stuck' needle, but needle that certainly needed attention.

Thanks all for the help.