Houstondave,
Slid under the truck this evening to take some pics and I think I found what you are talking about.

This is a pic of the plug that plugs into the tank with the two wires. My gas tank was recently replaced, so the ground wire and metal clamps even look somewhat new.


And this next pic is a little more to the right(drivers side) of the truck where it looks like there is a split in the wire



And lastly, I did not know what the metal hose is for the ran towards the tank but ended with a shiny silver tip, you can see it in the first pic and this is another photo of how it runs along the passenger side towards the front of the truck, any ideas of what this is or was? Ok for some reason, the picture inserted up at the top of the message.

james

 

Passenger side. Smaller than a fuel line. Has the fancy end on it.
Stock evaporative emissions line that would have (or might still) run up to a charcoal canister on the passenger side frame rail (or wherever they mounted them your year) and then with a big hose on up to the engine.

When they replaced the tank they either:
1. Found out the new tank didn't have the proper fitting.
2. Decided not to use it because it's "just more smog crap" to some even after all these years.
3. Just forgot to re-connect it.

Paul

 

I'm with 1Ton on his call. Based solely on mine: centered in the top of the tank is a rubber plug which has a fitting to connect a small hose (about 1/8" ID) - this has a flexible hose from there to past the front of the tank where it connects to a hard line to the carbon canister at front of the truck. This is one of those 'good' emissions controls which vents fumes from the tank into the carbon canister and keeps it from stinking. Often people buy a non-vented tank which does not have this fitting and just cap off the line to the carbon canister. If you do this, note you will need a vented gas cap (or at minimum drill a small hole in your non-vented cap to keep the tank from building up a vacuum as gas is used.) From the sender (the ring-enclosed round thingy in the middle of the slanted front of the tank) you will have 1) flexible gas line (I think 1/4"ID?) which routes to a hard line on the driver's side of the frame - that is your actual gas line. You will also have 2) the round 2-wire plug which plugs onto the sender's electrical posts. The rest of this has already been beaten to death above. Yes, the plug a few inches below the hose clamp in your pic looks like the connector which carries juice to the sender, so when you unplug it your gauge should drop to empty.

 

Question for "Houston Dave & 1Ton". Small hijack.....when pulling the sending unit out of the tank, " What size gasket/oring is needed to reseal the sending unit when reinstalled in the tank?" Thank you. Hijack over.

 

Good question. I have no idea of the dimensions. Only that you usually get one for the specific application. Yes, there are many that are the same, and very likely they were all the same within a vehicle lineup during certain years. Possibly even the same across brand lines for some vehicles, but I've always just ordered them for the vehicle the tank was out of.

I don't know if the ones that fit the EB's are the same for similar vintage pickups (note #9712 and #9772 for reference here: https://www.wildhorses4x4.com/catego...d=sending+unit) but they very well could be.
Thinking about that though, I don't think the ones in my '79 were the same as the '71, so that theory could be shot down right off the bat.

One thing that seems to be a sticking point with many is whether the original was using a seal with a round profile or a square profile or cross-section. Try to get the same that came out, since some will tend to squeeze out as you're tightening the ring anyway, but using the different profile will most likely make that even more of an issue.
A liberal dose of petroleum jelly on the seal and seal surface can help a lot with the install either way.

Your local auto parts store likely has them in stock, or can get them in a jiffy. Not sure what kind of pricing they would have, but you can see by our price they're not intrusively expensive. And we're not a discount site by any stretch of the imagination!

Hope that helps a little. Sorry I didn't have the dimensions specifically for your 78 or 79 (that's what this is for, correct?) but I'm sure one of the others seeing your question can answer the physical size aspect.

Paul

 

Oh, and it seems to me that on my '79 the two tanks were even different from each other. Doesn't the side aux tank have a different screw-on type plastic retainer, vs the twist-in steel unit for the rear tank, like the one pictured?
I think mine did anyway, but I have a long bed and the big factory tanks (49 gallons total) so that may vary by model too.

Just for our information, are yours long-beds, short-beds, style sides? Might make a difference.

Paul

 

yes, you probably need to adjust the float arm, a job best done with the tank out of the trunk.

When you get a new sender they usually get a round seal. On mine it had a square cross section; I did not like it. I posted at the time what size fit... I want say 128 but could be wrong. Search for “o-ring” and look for one of my posts in the results.

 

HoustonDave,

Unplugged it and now gauge drops to "0" . So I have eliminated that the dash gauge is not working properly, it's either a full tank of gas, or the sending unit is bad. The FULL gauge though is pegged at full, could not go any farther up, so I am guessing the sending unit. But I guess now I drive with a couple of gallons of gas in my truck to see if it ever moves.

james

 

based on everything you have described you have a dreaded “ full tank of gas”. Drive it a hundred miles or so and if you survive, you will probably see your gauge reading recede.

 

Lol!! I hope you are correct!! My list of things I need to fix are slowly increasing, took my truck this afternoon for a cleaning and the high pressure water confirmed that I need the seal on my driver and passenger window replaced, I kind knew this as the passenger window rattles in it's door.

james

 

If you think the list will ever stop growing, you are either delusional or have the wrong vehicle. Never owned a car yet that didn't need SOMETHING. There are about 10,000 repetitive posts on window/door seal sets, I think the consensus was that LMC's were not very good and Denis Carpenter's were among the best.

1Ton - mine is a longbed with the 38 gallon tank - I found the O-ring post, and it was #229.

 

Yea..... i'm not gonna lie, I think that is the fun part of having something like this. The opportunity to work on it and always having something to do. It would be boring to have a totally restored vehicle to take out on weekends. As for the window trim, I actually watched a youtube video last night about installing the trim and they stated that the LMC was his preferred trim, however I have more faith in his forum's members input. I think though the window trim is a little lower on the list of things to do, need to get my reverse lights working properly and insure my fuel gauge is registering properly first. Thanks for the Dennis Carpenter suggestion, will look at their part first.

James

 

Not entirely, but you're probably still correct. You can connect resistors with certain values, in line with that sender wire, and see if the gauge indicates in the specified zones, per the resistor values.
You could always siphon the gas into another vehicle...
If the gauge stays pegged on Full when you know the tank is nearly empty, then it could simply be the sender wire is pinched, tearing open the insulation and grounding the circuit. Hopefully not the sender itself.