71 Vapor Tank Hoses

[Richie G]

I'm doing an interior restoration on my late 71 and when I pulled the rear interior panels found a mess of the vapor tank hoses.  Seems the previous owner decided to patch work as best he could to ready for sale a combination of original braided hoses and all types of couplers and adapters to just make it work.  To be fair, there is no smell of gas so his connections seem to be nice and tight but I just can't let myself leave it that way after seeing it.  One issue I do have though, which may be unrelated, is that if the car sits for several weeks (especially in the hot 100 degrees days of Sacramento), I seem to get vapor lock and the mechanical pump struggles keeping the carbs going.  Starting the car requires full choke even in the dead of summer and then it dies when the carbs empty.  Once that happens, I have to "prime" the carbs with gas by pulling a rail to carb hose to fill the carbs then while the hose is off actually hand pump the gas up through the rails to get enough in the line to keep it going when starting it.  It's a total pain.  I'm not here to tackle that today, but maybe fixing some of these vapor hoses (especially the ones with the bends that are pinched shut) has a positive effect.

So back to the hoses.  I've read all kinds of articles here and elsewhere but can't seem to find an easy and direct answer to the question of what sizes and lengths each should be.  Since I don't seem to have end to end original hoses I can't just pull and compare very easily either.  My plan is to get the hoses, clamps, possibly a coil to create the magic 180 bend, etc. ready then go to a place that can help me drop tank and replace.  I have very limited access (and ability quite frankly) to drop tank and take this one step at a time.  So I'm hoping to find some help for a newbie.

To get this going I found as best I could a blank diagram to start from and added a color code to all the hoses.  My car is a 6/71 with the metal vapor tank but this picture seems to maybe be the older plastic ones?  Not sure if that impacts size or length of these hoses?  I began this project by looking for the hoses on the typical sites and was only able to find the front side hose in red.  Since it is one of the ones with the funky bends I figured at least start with what I can buy rather than build for someone like me.  If my research is right, the green one called the short rear hose also has a funky bend and most people use a spring coil to produce a safe bend and just buy a straight hose.  I'd be Ok with that I think.  BTW I just went to look at mine as best I could from underneath and sure enough its a rubber hose, hopefully fuel rated, and hand bent to the point its completely collapsed.  Maybe part of my vapor lock issue who knows.  As I mentioned earlier, my current setup has adapters mid hose, at the joints, and anywhere else you can think of so one of my questions is also, do I need adapters anywhere other than the one on the replacement fuel filler neck in light blue?  Assuming my tank nozzles are all good and healthy I assume its find the right size hose and slip it on without issue?

Can someone help fill in the gaps in my chart to make this a bit easier?  Oh and if possible, any advice on how to deal with this once I'm ready?  I've never emptied and dropped a tank but am willing to try with my limited capabilities.  Is there anything I'm missing here?

 

Edited February 22, 2023 by Richie G
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[ZNate]

Hi Richie,

I completed this same project on my 1970 240Z (same color) in September 2020.  You only want to drop the tank once, so do as much service to it as you can.  It was a pain to reinstall, but otherwise a straight forward project.

In addition to the hoses, I replaced or installed the following:

1. Fuel Neck (OEM)
2. Fuel Tank Lid Flap (ruined by PO using wrong fuel cap)
3. Fuel Tank Panel Shield (mine was missing)
4. Fuel Sender Connector Boots (old boots may be brittle)
5. Fuel Tank Rubber Strap Isolators

You may want to get a new O-ring & locking tab for the fuel sender, in case you need them.  If your fuel gauge is not working correctly, replace the fuel sender now.

Consider replacing the associated Gas Tank Vent Hose Boots and Grommets.  The are available from Banzai Motor Works (GF-17, 18, 19 and 20).  Not sure how many of each you will need.  Luckily, mine were still serviceable.

Based on information at:
https://woodworkerb.com/home/datsun-240z-rebuild/240z-fuel-tank/

I ordered five hoses from JBugs in CA.  They are cloth braided and appear to be the same as the OEM hoses you are replacing.  When you order, make sure all five are in stock.  Otherwise, they will charge you for all five and send any out-of-stock hose later (when your project is already completed).  In my case, I was sent four of five and I luckily sourced the missing hose (9 x 3MM) from a local, national auto parts store.

I did not replace the simple, thin non-clamped vent hoses attached to vapor tank, so be careful removing them.  I have no details on type or length.

For the “funky” bend hose connection to work, I inserted spring coil (like on older screen doors) into the hose to make the connection work.

JBugs Order: 
Note: Hoses are sold by minimum length requirements.  In other words, longer than you need.
1. N203741   VW German Cloth Braided Breather Hose, 12X3.3mm, Length: 10
2. N203701  VW German Cloth Braided Breather Hose, 17X2mm, Length: 10
3. N203551  VW German Cloth Braided Fuel Hose, 5X2.5mm, Length: 3
4. N203571  VW German Cloth Braided Braided Fuel Hose, 7X2.5mm, Length: 3
5. N203761  VW German Cloth Braided Fuel Hose, 9X3mm, Length: 10
Total cost: $116, with free shipping in 2020

Tank Removal Process:
1. Disconnect battery
2. Loosen right rear wheel
3. Jack up car
4. Remove right rear tire remove rear interior panels (I think you have already completed this step)
5. Spray rusty strap nuts & bolts in advance
6. Drain the tank well; any remaining fuel can be drained by removing the fuel sender
7. Remove the wires for the sender
8. Carefully remove fuel hoses next to sender
9. Remove filler neck clamp at tank
10. Carefully remove hoses from expansion tank
11. Support the tank; use a floor jack or transmission jack & small piece of plywood
12. Take off the straps and lower the tank
13. Lower 4”-6” and disconnect remaining hoses
14. Pivot tank forward a bit due to the rear skirt
15. Detach all of the vent hoses, the filler hose & fuel lines
16. Remove the tank

If you have no evidence that the tank was previously removed and cleaned or your fuel filter gets dirty quickly, have the tank cleaned.  You will probably want to repaint the the exterior.

Tank installation is is reverse order, but note:
1. You may have to raise the tank to connect some hoses.  Some do not have much room for slack.
2. The tank drops out easier that it goes back in place.  I have to fight with mine to clear the rear skirt.  You may want to put good quality painters tape along the skirt to avoid skirt damage.

Good luck with your project!

Nate
 

[Patcon]

Great write up!

[Richie G]

Znate thats great advice thanks so much for the thorough write up.  My hope is that all I have to do is get these hoses straightened out.  The PO has already installed new sending unit, filler tube, and sprayed gobs of undercoating all over the tank but the filter is always crystal clear so maybe they at a minimum did a boil out of the tank.  I just don't get why you'd do some of the basics but leave such a mess of these hoses.  I mean some hoses have three different transitions for couplers and fittings.  Why?  Ok you didn't want to buy braided hoses, but at least home run the hose to the tank, not multiple transitions.  The car was a "partial restore" in that they did rebuild the numbers matching engine, refreshed a bit of the interior but not all, did a decent glass out two stage paint job, but at some point was in it to make money on the flip.  Original paint and 50 years of dirt behind these panels, under the new rug, some surface rust under the sound deadening, etc.

I'm at this point where my limited access / space / time has me fearful of getting it out but no way to get it back in lol.  I'm going to buy all the supplies I need and then gauge where I'm at.  Thanks again for the advice and quick reply.

[Richie G]

Znate you talking about something like this for the spring?  Which size would I get for the short hose on the rear of the tank?  And once I have the right size just slip it inside the hose and form the bend?  What keeps the hose in place, doesnt the spring want to flex back to straight?

 

[ZNate]

Hi Richie,

That is the correct type of door spring.  The door spring keeps the hose from kinking or bending too much.  It does not turn a straight hose into a bent hose.  

To find the correct spring, I took the old bent hose portion and the new hose to the local hardware store.  I searched through the door springs to test spring diameter and length until I could match the old bend.  Easier than I thought.

Sorry I do not have the spring size.  My Z and all receipts are in WI and I'm in FL for the winter.

My 70 240Z has a similar history.  A partial restoration (or preservation work) by the second owner in 2012-13 (134K).  I became the fifth owner in 2019 (137K) and found similar issues not addressed.  I spent the past four summers sorting it out and it runs just like a new car.  Starts quickly, reliable, comfortable and quick.  I installed a 280ZX close ratio 5-speed and a JDM 3.90 rear end.  What a performance boost.

Good luck, Nate

[ZNate]

Richie,

A couple extra thoughts.  

1. Take photos as you go and label the hoses as you remove them.  Much easier to match as you reassemble.  

2. The hoses on the tank are difficult to remove; 50+ years of service.  Since they would not slide off easily, I cut them as I lowered the tank.  With the tank out I was able twist or slice them from the tank connection.  Later you can reassemble the cut pieces to determine the true length.  Make them a little longer so as you raise the tank back in place you can cut off any excess.

3. Cut enough of the "funky" bend hose for matching with the new hose and spring at the hardware store.

Nate

[Patcon]

$277.77

All 10' lengths in 2023

[Richie G]

Thanks Nate.  I took a shot on the 5/8 x 8 1/2 spring from amazon which is probably going to be a tight fit for what i believe will be the 17 mm hose for that section.  I'm thinking the tighter the better but if not amazon has free returns and they come overnight.  I'll just have to play with the bend since the hose there now is completely mangled / pinched totally shut from what i can see peeking under the valence.  It's certainly part of the PO hack job in place to deal with.

I like what you did with your upgrades, impressive.  I'm a ways from that I'd expect and as best i can tell its all stock right now for the next steps.  I kind of like the idea of trying to keep it as accurate as I can but realize this won't end up a concourse car by any means.  I have this idea in my hand that is grand for someone like me and will take the turns in the road as they come.  I can't change the purchase I made at this point 20/20 hindsight and all but am really enjoying the work I have ahead, the learning, and even some of the mistakes I would have caught earlier in the process.  

Couple of other questions if you don't mind.  You mention the shield you replaced.  Newbie question where is that exactly and any links to pics to compare would be great?  Yours was missing and mine might be too without even knowing it.

The other question was back to my actual problem of starting after a few days of sitting.  Another newbie I'm sure.  I pretty much can predict the problem because I can see there is no fuel in the filter and the fuel level has probably dropped back down into the hard line.  If i see fuel in the filter it seems to be fine.  Is it normal for the fuel to drop like that after a few days of idle?  Is that drop some indication of pressure loss somewhere even though I don't see any significant leaks?

[Patcon]

I believe he is referring to the extra metal in the passenger side wheel well

Zcardepot offers this piece

[ZNate]

Hi Richie,

Patcon's photo shows the correct shield.  Nice that new replacement shield is available.  The ZCarDepot catalog mentions use of stainless steel screws too.  The shield I purchased off of eBay shows its age and matches the "52 year old" inside of my Z's wheel well.  No painting required.

Your Fuel Line/Filter Issue: The other question was back to my actual problem of starting after a few days of sitting.  Another newbie I'm sure.  I pretty much can predict the problem because I can see there is no fuel in the filter and the fuel level has probably dropped back down into the hard line.  If i see fuel in the filter it seems to be fine.  Is it normal for the fuel to drop like that after a few days of idle?  Is that drop some indication of pressure loss somewhere even though I don't see any significant leaks?

Response: I'm assuming your fuel filter is mounted on the wheel well next to the trouble light.  Fuel is sucked from the tank and out through the top of the filter to the fuel pump, then to the two carbs.  I would assume the loss of fuel in the filter (and unprimed fuel pump making the engine harder to start) is from an air leak between the carbs and the fuel filter output.

1. Are the fuel line hoses clamped tight? Sometimes hoses clamped too tight compromise the hose, leading to fuel or air leaks.

2. How old are your fuel hoses?  My Z had six year old hoses that were junk.  Dry and brittle, plus clamped too tight.

3. Check the carbs for air/fuel leakage.  Check the short hose under each carb too.  They can get brittle from exhaust manifold/header heat.  Check for drips after running the engine, but only service the hoses with a cold engine.  Replacement hoses are available from ZTherapy.  The hoses are unique, but inexpensive.  Do not use any other type of fuel hose.  Try to salvage the wire hose clamps for reuse, but ZTherapy does provide a different type of clamp.

4. What about the fuel pump?  They seem to last a long time, but maybe there is an air leak.  With a good quality screwdriver, try tightening the 11 screws on the pump.  Just be careful to not damage the screw heads.

5. After completing your fuel tank hose work and checking 1-4 above, if there is still a leak that drains your fuel filter (and probably your fuel pump), consider rebuilding or replacing the fuel pump.  ZCarDepot does have a couple types of replacement pumps.  If you want to keep the Z original, you can also rebuild your existing Nikki pump, using internal parts from a similar Nikki pump.

Good luck with your project!

Nate

 

[Richie G]

Nate you are awesome.  I'll be honest here, i would have expected an air leak from filter to tank which for me would have been harder to troubleshoot with limited garage access.  Why i say that was because I also found out after purchase that the PO had actually coupled the supply hard line about mid body in the tunnel.  It was only revealed when I had someone drop the tranny to address a rear leak.  It was a rubber fuel line coupling two hard line sections that we've temporarily addressed with another hardline section but even that I want to replace end to end at some point. Why someone would do that, rubber fuel hoses near a section of hot exhaust and tranny tunnel, is beyond me.  Also, I would notice bubbles flowing in the fuel filter even when it was running well so i thought for sure the air leak was coming from tank side of the filter.

Tank shield is in place and looks good although the PO really went to town on undercoating  lol.

Yes filter is in the typical place (although after market generic kind at the moment).  The car currently has fuel hoses the PO put in I think end of 2020 as part of his restoration.  They seem like they were new at the time so about 2 1/2 yrs old but I had on my list to replace them with correct braided.  I have as part of this project all new wire type clamps and braided 6 mm and 8 mm hoses (I believe are the right sizes from some advice previously here).  I do not have replacement bowl hoses but will see if they need it and address at same time.  From what I recall when I first noticed this and did a bit of an inspection the clamps did not seem too tight but I did notice a crack in the heat spacer between the pump and the engine mount.  I've also purchased a replacement spacer / seal and the idea was to replace that, all fuel hoses, a correct filter, and all the clamps and see if that corrects this.  The pump also seems to have been new at time of restoration in 2020 so I wouldn't expect that to be the issue unless he fiddled with it and like you say maybe the bladder is having an issue.  I'll be sure to check screws when I do all this.

So I think my tasks are to

1.  Replace the hoses / filter and ensure the new clamps aren't too tight.

           When i do, am i correct in using 8 mm for the 3 hoses supplying the rail? (line to filter, filter to pump, pump to rail) and 6 mm for the rail to carb and the return to hardline?  Currently PO has 5/16 for those first 3 supply hoses, 1/4 for the carbs, and 3/16 for the return.

2.  Replace broken pump spacer / seal and ensure pump screws are tight but not too tight.

3.  Check carb bowl hoses and address if needed.

         When you say check carbs for air / fuel leaks how do i do that other than these hoses?

 

Thanks again for being so patient with me, I'm learning a ton and loving it.