Aux tank fuel sending unit install

[lbuch40]

I am installing a new sending unit and after watching several videos I haven’t found one with plastic flange attached to the tank and the metal locking ring attached to the plastic flange.
See photos.
The metal locking ring was attached to plastic flange with just 3 small little tits from the plastic to metal locking ring. Very cheesy. Of course the metal ring came off.
Can it simply be screwed back on with short screws? Maybe also some adhesive?

 

[Speedrdr]

Is the aux tank original? Also what year? That may make a difference as to my knowledge and assistance. Lol

 

[lbuch40]

It’s a ‘69. I don’t believe it’s the original tank, but I might be wrong able to confirm with some research.

 

[lbuch40]

Is the aux tank original? Also what year? That may make a difference as to my knowledge and assistance. Lol

The aux tank was installed in 2012 , purchased from Bronco Connection.

 

[Speedrdr]

I didn’t have any problems using a poly-type adhesive with appropriate sized screws on an auxiliary tank. Never had any issues with leaks for the 4 years after the repair. You might consider cutting a “gasket” out of an inner tube. Scuff that area on the tank, apply some contact cement to both the tank and one side of the tube. When the glue is dry to the touch, put the “gasket” on the tank and roll it to get good adhesion.
That should let you screw everything together with no leaks…SHOULD not leak, but that’s just how my repair went.

 

[lbuch40]

Thanks for the reply. After examining some photos from different but unrelated posts I realized that the little tits holding the metal locking ring on to plastic boss on the tank were actually remnants of rivets that had mostly rusted off. So I cleaned up the metal, painted and reattached it with some silicone adhesive and 3 self-threading screws, The mating surface does not come in contact with gasoline, so it won’t be the source of any leaks.

 

[Speedrdr]

I looked for the aux tank that I had to replace…6” tear in the top…but couldn’t find it. Cannot remember where my replacement came from but it was very well secured.

I think what you’ve done will work well for you.

 

[lbuch40]

Had trouble getting the new sending unit installed and discovered the fuel pickup tube is s about an inch longer than the old one so it was hitting the bottom of the tank. Talked to the folks at WildHorses and they verified it would be no problem to reduce the angle on the pickup tube by bending it. I did that very carefully….and it went right in. I also bent the float arm up so it matched the the level of the intake tube to show empty..
Filled with gas and no leaks. Unfortunately though now the gauge only shows 1/4 tank when it’s actually full. So maybe bending the float arm wasn’t a good idea….or its hitting something inside the tank?
Anyway, I’m back to pulling the sending unit out again for additional diagnosis.

 

[Speedrdr]

Was the float arm hitting the bottom before you bent it? If not, I’d drive it until you run the tank empty and drop the aux tank and bend the float back to where it was previously. Should correct your readings.

 

[lbuch40]

I just assumed the float would hit the bottom because it was originally at the same level as unmodified pickup tube.
My theory was that I would want the float to show empty approximately the same time as the gas dropped to the bottom of the pickup tube.
My plan is to do exactly as you suggested. Although first I will check the gauge reading as I move the float up and down. If the gauge reads correctly through the range of motion that will rule out any wiring issue between the sender and the gauge.

 

[Oldtimer]

If you have an ohm meter, check resistance range of sender. Ford factory gages expect to see 10 to 37 73 ohms.

 

[lbuch40]

Yes, I checked it before installation. The range was about 9 to 75. My understanding is that is correct range. Is there different specs between an original factory gauge and an aftermarket?

 

[Oldtimer]

Typo on my part; Ford factory gages expect to see 10 to 73 ohms.

 

[lbuch40]

Ok . Good to hear. Was hoping there wasn’t another variable to consider

 

[lbuch40]

Took sending unit back out. Verified that the gauge was roughly corresponding correctly to the position of the float.
Bent the float rod straight….back to its original configuration.
Gauge still never reads over 3/8 with full gas in the tank.

When I looked at another post about the function of 4 different entry points in the aux tank, one is to allow the tank to vent while filling. When I look inside the sending unit hole, there appears to be a tube extending horizontally about 12” into the tank from the vent connection. Is this “normal”?

I am wondering if the float is getting hung up on that tube.

Seems like a vent tube should be angled up to the top of the tank instead of straight in?

 

[lbuch40]

Has anyone ever seen a tube extending inside the aux tank from the vent nipple??

I can’t figure out what the purpose would be and I believe it may be interfering with the sending unit float.

 

[mrdrnac]

Yes mine was that way with the vent tube extending into the tank quite a ways. If I remember correctly I had to bend the float arm and re-position the float in the arm so it stuck out from the arm in the opposite direction as it was originally to clear that vent tube. I also soldered an extension of copper tubing onto the arm to make it longer. My end result was it reads all the way down to Empty and up to about 7/8 Full when the Tank is full.

Viperwolf1 has a good picture in his Thread about increasing capacity of the aux tank.

Increased Aux Tank Capacity

Got my hands on a spare aux tank from a '73 and figured I'd fix it up to replace mine which leaks a little. First thing I did was measure the capacity. It holds almost 12 gallons when standing on end. I know the rated capacity of a '73 tank is 7.5 gallons but the early years (before venting)...

classicbroncos.com

 

[lbuch40]

Thanks for this good information. I was wondering if the PO had added that tube for some reason. I couldn’t figure out why that tube was so low in the tank. After reading the thread Viperwolf started, now I think I understand what’s going on .
Sounds like definitely some modifications are needed either with the tube or the float.

I wonder if there are some schematics with dimensions out there showing the inside of the tank along with the sending unit pickup tube. The sending unit I got from WH was about an inch longer than the broken one I took out.

 

[lbuch40]

I just discovered that not only does the vent tube extend about 10" into the tank, also the FILL tube extends in and angles toward the bottom of the tank. Has anyone else seen this on the auxiliary tank? What is the purpose?? I'm pretty sure that's what is interfering with the float. Unfortunately, I don't believe I can bend the float arm far enough to one side to avoid that giant 2" tube inside the tank.

Any ideas for a solution?

 

[DirtDonk]

I thought someone was finally reproducing the original design sending unit. Maybe they stopped, or maybe there were actually different versions over the years?
I’ll try to check that out.

Regarding the tube extension, I always thought that was done to help maintain the air gap (for lack of a better term?) at the top. Both for expansion when warm, and especially for the venting of fumes.
Your ‘71 would fall into that category because the charcoal canister was added in’70 to all Broncos.