What size is the tank vent hose?

[Cubey]

Searching the archives, I couldn't find any mention of the tank vent hose size.

Is it 3/8" or larger?

If so, I think I might tie in my electric fuel pump regulator's return line to that instead of the engine's 5/16" return line.

The regulator calls for 3/8" or larger, or else the regulator won't work properly, causing higher output pressure than desired. The 5/16" line already has to cope with the emgine's returned fuel, so it might get overloaded.

 

[Cubey]

The rain finally let up so I could actually go outside and look. Wow, it looks like a 5/8" hose! Plenty big! And it has a huge outlet into the filler neck too. I need to replace at least the tail end of the vent hose (the filler isn't looking too good either!).

It might be a bit hard to find a brass 5/8" to 3/8" tee. Plastic might work, since it doesn't have to hold any pressure really though, just flow the returned fuel to filler neck for it to gravity drain back in.

You must be registered for see images attach

You must be registered for see images attach

 

[Garbage_Mechan]

One cool thing your rig has that the most of the rest of us need is that 5/8 tank vent. I have 2 rigs I’m working on installing them on. Your pic gives me some reference as to how far down to tap in the 5/8 tube.

 

[Garbage_Mechan]

As to returning the fuel from the regulator here: yes it will work fine but be just slightly less than ideal. Reason being in fluid dynamics we want to return flow back to tank below the level of fluid in the tank to prevent creating air bubbles in the fluid.

Can you get the sending unit out without dropping the tank?

 

[Cubey]

One cool thing your rig has that the most of the rest of us need is that 5/8 tank vent. I have 2 rigs I’m working on installing them on. Your pic gives me some reference as to how far down to tap in the 5/8 tube.

It fits truck lane nozzles too, unlike my F250 with a threaded cap.

That pic is my rear tank btw. It's a bit easier to reach under it with my phone than the front. Plus my front tank has a plastic bag zip tied over the filler, due to me losing a cap at a station, which I realised 100 miles later.

As to returning the fuel from the regulator here: yes it will work fine but be just slightly less than ideal. Reason being in fluid dynamics on wants to return flow back to tank below the level of fluid in the tank to prevent creating air bubbles in the fluid.

Can you get the sending unit out without dropping the tank?

Are air bubbles a big deal when you are filling your tank? Because that's basically the same thing, fluid is pumped into the filler neck and it drains down into the tank.

Maybe a check valve on the vent would work, so air can escape when filling up but fuel can't be pumped through the vent to the tank, only to the filler neck.

It might be less than ideal but it's better than having way too much fuel pressure at the IP due to an undersized regulator return line.

Plus if tied into the 5/16" engine return line, it could potentially pressurize the injector caps and the tiny lines, which wouldn't be a good thing. It expects 3/8" or larger, so the fluid would go anywhere it can if bottlenecked under pressure.

 

[Cubey]

Oh, and probably no to removing the sending unit without tank dropping.

 

[Cubey]

Hmm, I see what you mean:

xc_hide_links_from_guests_guests_error_hide_media

I guess I'll plumb it to the 5/16" return line and hope for the best.

Over in my pump conversion thread, Wes's opinion is that 5/16" would be enough: https://www.oilburners.net/posts/1047275/

I might leave the mechanical pump installed to the block (but unhooked from the fuel system, with the ports sealed off) until I test things out, in case something is bad wrong and I end up needing to revert to mechanical.

I'll be out $115 for the 105p if it doesn't work well for my needs, I guess.

 

[Philip1]

Would it be possible to plumb the regulator return into the supply line between the tank and pump?

Sent from my SM-G975U using Tapatalk

 

[Cubey]

Would it be possible to plumb the regulator return into the supply line between the tank and pump?

I thought about that, but then the pump would be fighting itself to a certain degree, pulling from the tank while also sucking in from the return and also pushing on the return.

Plus.... fuel pumps make fuel warmer. It might overheat the pump if it keeps immediately recycling a portion of the same fuel repeatedly. With it returned to the tank, it gets to cool off when mixed back into the tank.

Splitting it between the return line and vent would probably be better, half as much would be dropping back into the tank from the vent, causing less air. Running it such a way that the 5/16" engine return is the primary regulator return, with the vent hose being the overflow/excess (run higher than engine return) would probably be a good way to do it. That way the 5/16" can't totally bottleneck, any extra would have no choice but to go to the vent/filler neck. Then the injector return caps can't get pressurized from the pump/regulator if the 5/16" line is at full capacity. There's no way it would be able to bottleneck both the main 5/16" return plus another 5/16" or 3/8" line leading to the vent.

 

[Cubey]

Quite honestly? It would probably cost me less to just return the 105P and buy a Holley Red from Advance Auto for $125 w/tax & free shipping. It doesn't need a regulator (it's rated 5-7PSI) or a return line.

It's 10GPH less but eh... 95GPH would be fine for an 085 IDI. I'd have to buy another $20-30 in fittings and hose to put in the return line. I wasted some money on fittings for this regulator setup, but... eh, maybe I'll use them someday for something else. Or I can pay return shipping to get most of the money back.

I just noticed that the Mr Gasket 105P pump seller I bought from offers free returns, so I don't have to pay return shipping on that.

I'll sleep on it... but yeah, that sounds like a better pump for an IDI.

None of these pumps are rated for diesel though, so how long any of them will last is up for debate. Diesel is a bit thicker than gasoline, but more lubricated. But at least with the Red pump, the repair kits available for sure fit them for about $25-30, so if they don't hold up well to diesel long term, they can be repaired at least.

 

[aggiediesel01]

One cool thing your rig has that the most of the rest of us need is that 5/8 tank vent. I have 2 rigs I’m working on installing them on. Your pic gives me some reference as to how far down to tap in the 5/8 tube.

In this album you'll see the other parts to build the larger fuel necks.

View media item 622

 

[Garbage_Mechan]

Yep, that’s what I did pretty much. One truck waiting for the engine to go in, the other waiting for me to find the energy to pull the flatbed off. It ****** me off every time I fuel it but just slightly less than enough to go home and rip the bed off......