Fuel Sender/Gauge

[240z70]

My tank leaks.  Not sure if i will be able to get it fixed or if i have to have one built.  History:  current tank is aluminum rectangle type custom with no sending unit.  whether i fix or build i want sending unit.  but from what i have heard the 1970 240z sending  is 90-10 ohms.  Problems:

1-Tank does not have sender so hence no sender retainer to attach the retaining ring for use with the original sender.

2-cant find a retainer to weld to the tank so that the original sender can be used.

3-Might not have enough room for fuel sender arm and may have to use vertical; tube or uncovered.

4-all aftermarket ones are 0-90 or 70-10 or some other ohms but none are 90-10 and readily available

Questions:

1-Does the gauge for the 240z fuel level need a 90-10?

2-Can i use a 0-90 and what would that do since it is reversed the ranges are different?

If anyone has answers I sure would appreciate including possible alternatives or where to obtain a 90-10.  I need to find out asap to either repair or order custom tank.

THanks.....

[grannyknot]

Can you not just get a used 240 tank?  I got around the 90-10 ohm problem by using a Speedhut fuel gauge that is programable.

[240z70]

Unfortunately no.  The exaust system was revamped previously and goes from the headers into a 2.5 inch pipe, then splits into 2 ea 2" pipes and each goes to the side of the car.  the tank is aluminum and from the top looks like a rectangle with the front corners cut off in order to accomodate the side exausts.  The top of the tank is flat because the tire well was removed so it fits straight up against the rear deck.   For me to go back to the original tank i would have to change all the exausts pipes and provide some type of support for the tank -both new attachment points and a top supGo to this postport sin the tank would no longer be pined up against the spare tire well which does not exist anymore.  Sender is to go inside the little hole you see in front of the fill neck. 

Edited August 24, 2018 by 240z70
messed up the pic attachment.

[zKars]

Classic Instruments SN38 can be built either 0-90 or 90-0. It's an arm style sender. 

Having a reversed 0-90 just means full = empty, empty = full. At least it bang on at half a tank!   Hahahahaha

[240z70]

Just an update:  I was able to find a TUBE type fuel  level sender: 

Length:    9 - 1/16 inch

Attachment: SAE 5-hole  pattern.

OHMS:  90-10  

Condition:  New unit.

Type: Tube

This should fit the tank just fine since it is 9.5 inches deep, and it is 90-10 ohms just like the original lever type that came with the car, so the OEM gauge should not have any issue with it.  When it reaches 90 ohms, I should have roughly over a gallon left as reserve, so based on ~20mpg, this should give me about 15 to 20 miles to find a gas station before it is completely empty as long as I dont stomp on it...Perfect...

This is  great news for anyone who has an aftermarket fuel tank.  By it being a tube type, I am not restricted by the available room for proper lever operation , and also have the opportunity to utilize cell foam in the main chamber to minimize sloshing between the existing baffles due to the protection that the outer tube offers by not letting anything hit or lodge against the interior level indicator components and preventing their operation.

Thanks for all your help, it gave me different ideas and i even thought of trying to locate a 10-90 and mounting it on the bottom of the tank, but, thats too risky due to potential leaks...and I was actually contemplating using your example of 0-90 and just reading the gauge backwards or trying to find a gauge that would work with it and look somewhat like the original gauge..  Even a 73-10 was beginning to look like a potential option.  But now if everything works as planned, I dont have to do that.

This weekend planning on making the fill mod to fill it from behind the license plate and wiggling out any connection issues (vents, hoses, neck attachments, splash neck cup, etc...).  If it all works as planned I should have the fuel issue engineered and finalized within a couple of weeks.

[Patcon]

Where did you source it?

[240z70]

England.  No one in the US sells it.  They air mailed it and I picked it up from FED EX yesterday.  Pretty quick shipment considering where it came from.  Hopefully I will be able to install it this weekend.  Gotta make the main hole and the 5 SAE bolt holes for it on the aluminum tank.  Gonna use a holesaw to make the hole. I also still have to find the wire under the car that leads from the sender to the gauge.  I have not seen it yet.  Hopefully no one removed it... If you guys know where it is supposed to be, and or have pictures, please post.  Color code would also be helpfull if there are more than one wire in the bunch...  Not sure if it is mixed in with the light harness for the back lights or if it comes in under card independently....????

Other news: part of my gas tank dillema was to:

1-repair or replace the custom aluminum gas tank due to leak---DONE-repaired

2- find a sender 90-10----done, and purchased/delivered. ---- DONE

3-Change fuel filling location from inside hatch to hidden behind license plate, custom make gas cap ---DONE  Pictures  with wife holding it  partially open, and full open, are attached, spring is strong so she had to hold  it.  Not the best quality but it was night time. Some cosmetic work to be done still and on the original holder holes, i will put rubber stops so the  plate doesn't smash into the car when if you let go suddenly....  removed the plate number in paint and put on fictional number..didnt come out too good  but better than just the white out plate.....LOL

4-Install sender, Tank, fuel connections from filler to tank and to vent tank, test tank w/fuel and gas gauge ----   To be done

 

 

Edited September 6, 2018 by 240z70
Changed lic plate # to more appropriate...LOL

[zKars]

We need more details about the sender retailer, such as a website or name. Great find!

The wiring comes from a connector that is next to the right rear tail light harness behind the plastic trim panel in the hatch. This sub harness then goes through a grommet through the hatch floor to the sender. It also connects to a ground bolt (inaccessible above the gas tank....) and also has a wire for an electric fuel pump. The sender wire is yellow, the fuel pump wire is green.

Just a thought about your rear mount gas filler neck.  Remember that while filling, you need a 1/2-5/8" vent hose connected back to just inside the filler neck, to allow air to escape or you will have a real witch of a time putting gas in the tank. 

Edited September 6, 2018 by zKars

[240z70]

Here you go:  Merlin Motor Sports England

https://www.merlinmotorsport.co.uk/

As far as the fuel neck vent...Yep its there, but when I finally get a new tank rebuilt, since this one is a bit thin and old and I dont know how long the repair will last, the tank will wind up with 3 vents, one front 2 sides, which will connect to fuel pancake on side wall.  The pancake is triangular and has 5 lines, 3 for the tank, one to the fuel neck, and one venting to the exterior with a anti tip valve and a flame arrestor valve on the end.  This its covered in case of upside down spill  and flame/sparks near the vent tip.  On this build, i will use the fuel neck connection, and the vent and cap off the other 3 nipples since i am not drilling anything else on this repaired tank...  New tank will look more like this and i will be able to use same sender, while increasing tank height from 9.5 to 10 inches...Final Fuel Tank Design for new tank.pdf

Thanks for all your help.  Here are some pics you may like to see.

[240z70]

UPDATE

The fuel fill was installed behind the license plate.  Works great.

A new Custom Aluminum Tank was manufactured by a company in the East Coast.  It was mostly according to the drawing except that I changed the fittings to slip on hose instead of AN threaded.  I also went with 3/16 inch thick aluminum and 3 baffles, two from front to back and one from side to side.

The vents (3) and the return (1) were 3/8" and the draw was 1/2".  

The tank and sender were installed, however I still need to install the vent tank(Pancake).  The sender is not yet wired in.  Need to identify which wire is for the sender..

A new Aluminum 4-core radiatior was also procured and installed with silicon hoses, after the system was flushed.   A mixture of 50/50 and 100 was utilized to bring the coolant closer to a 70/30 which is the optiomal for increasing the boiling point.  A bottle of WaterWetter was also utilized in the system.  All works good.

Still a lot to do but buying parts when able to locate them and slowly changing/updating them.

Edited December 16, 2018 by 240z70
typo on thickness of tank.

[zKars]

All very impressive.

Did you actually use 5/16 in thick aluminum to fabricate the tank? Misprint? Definitely bullet proof if it is.

 

 

[240z70]

Sorry.  it was a typo.  the choices I pondered were 1/8  with a stainless shield 1/16" underneath or just go thicker with a 3/16 aluminum and no shield. 

Decided to go with the 3/16 Alum.  If i had gone with the stainless shield it would have cost a decent amount in order to form the sump etc.. so i decided to go thicker on the tank

and share the extra strength all around in its thicker construction.  If a rock does hit the bottom, then perhaps the difference in thickness with help and if it has to be re-welded to

repair any issues, there is more material thickness to play with... Also its overall rigidity is greatly increased... I have the original 1/16 alum tank and its crap in rigidity.

http://www.boydwelding.com/

 

Edited December 16, 2018 by 240z70
added link to company that made the new tank