New fuel tank and sending unit weirdness (Questions)

[Rembrant]

A week or so ago I put 5 gallons of gas in each dry tank with new senders (16 gal side tank / 19 gal rear tank) and found the needle came up to the empty line for both tanks so I was happy to be on EMPTY and have 5 gallons left.

OK, I am getting my truck back in a few days and I need to rectify this fuel gauge issue before I reinstall the bed, so I need to come up with a plan. Dave, you mention that yours is reading empty with 5 gallons in it, and that's cool, but I believe my original tank was reading empty with more like 2-2.5 gallons in it. The few times I drove it any distance, I drove it until it was empty (on "E", or below) and to fill it took 14 gallons.

I guess to start I'm going to drain as much gas out of it as I can, and then put 2-3 gallons in it and then bend the sender float arm until it reads "E" on the gauge. Would this be a reasonable or unreasonable thing to do?

Anybody?

My issue is that I really won't have much time to play with this before putting the bed back on.

I'm also going to check and adjust the plastic vent tube if required. I know this thing will work, I just need to hold my tongue right.

Ok go I got my old Bullnose back late today.

Fuel gauge was sitting between “E” and 1/4 tank, so at the 1/8th mark more or less. I removed about 42-43 litres of fuel...about 11 gallons I guess.

Interesting to note I found the filter sock had fallen off the end of the sender. I had to fish it out of the from the front of the tank with a piece of wire. No biggie, I’ll fix that.

I bent the float arm but couldn’t get it to read past 1/2 tank, even with the 11 gallons in there. So after I drained it, I put 2.5 gallons back in, and the gauge goes to “E” when I turn the key on. I don’t really know what it will do until I fill it back up. The way it was, I think the float would have had to almost hit the top of the tank to read full, which makes sense based on how it was working.

The sender looked fine, it just almost seems like it’s too short for the tank.

Does anybody know how far the pickup tube is supposed to be from the floor of the tank? I’m trying to tweak everything to get the right balance.

Right now the pickup tube is just barely submerged with 2.5 gallons in it. I can’t tell if the float is floating or if it’s bottomed out. I will check that tomorrow.

 

[Rembrant]

Ok go I got my old Bullnose back late today.

Fuel gauge was sitting between “E” and 1/4 tank, so at the 1/8th mark more or less. I removed about 42-43 litres of fuel...about 11 gallons I guess.

Interesting to note I found the filter sock had fallen off the end of the sender. I had to fish it out of the from the front of the tank with a piece of wire. No biggie, I’ll fix that.

I bent the float arm but couldn’t get it to read past 1/2 tank, even with the 11 gallons in there. So after I drained it, I put 2.5 gallons back in, and the gauge goes to “E” when I turn the key on. I don’t really know what it will do until I fill it back up. The way it was, I think the float would have had to almost hit the top of the tank to read full, which makes sense based on how it was working.

The sender looked fine, it just almost seems like it’s too short for the tank.

Does anybody know how far the pickup tube is supposed to be from the floor of the tank? I’m trying to tweak everything to get the right balance.

Right now the pickup tube is just barely submerged with 2.5 gallons in it. I can’t tell if the float is floating or if it’s bottomed out. I will check that tomorrow.

PS: I think the original tanks were specified at 16 gallons ya? My usually fillips used to be about 14 gallons so that makes sense.

This new aftermarket tank is advertised as being 16.5 gallon. I don’t know if it is actually different or just the same and labeled different.

[Rembrant]

PS: I think the original tanks were specified at 16 gallons ya? My usually fillips used to be about 14 gallons so that makes sense.

This new aftermarket tank is advertised as being 16.5 gallon. I don’t know if it is actually different or just the same and labeled different.

Ignore my awful spelling lol working on my phone tonight...

[Gary Lewis]

Ok go I got my old Bullnose back late today.

Fuel gauge was sitting between “E” and 1/4 tank, so at the 1/8th mark more or less. I removed about 42-43 litres of fuel...about 11 gallons I guess.

Interesting to note I found the filter sock had fallen off the end of the sender. I had to fish it out of the from the front of the tank with a piece of wire. No biggie, I’ll fix that.

I bent the float arm but couldn’t get it to read past 1/2 tank, even with the 11 gallons in there. So after I drained it, I put 2.5 gallons back in, and the gauge goes to “E” when I turn the key on. I don’t really know what it will do until I fill it back up. The way it was, I think the float would have had to almost hit the top of the tank to read full, which makes sense based on how it was working.

The sender looked fine, it just almost seems like it’s too short for the tank.

Does anybody know how far the pickup tube is supposed to be from the floor of the tank? I’m trying to tweak everything to get the right balance.

Right now the pickup tube is just barely submerged with 2.5 gallons in it. I can’t tell if the float is floating or if it’s bottomed out. I will check that tomorrow.

I don't "know", but I'd think that the pickup tube should be almost to the bottom of the tank. Otherwise the gas at the bottom of the tank can't be used.

And while that means you'll also potentially suck up some sediment, that's what the fuel filter is for.

[ArdWrknTrk]

I don't "know", but I'd think that the pickup tube should be almost to the bottom of the tank. Otherwise the water at the bottom of the tank can't be used.

FIFY...

I hope this hijack isn't inappropriate, but I want to say that I changed both tanks and senders about four years ago.

I could not find the one year wonder '87 senders, so I went with '86 mechanical pump senders.

These read completely wrong, so I've been just watching mileage with fill ups and figure I need gas around 160 miles per 19 gallon tank.

Gary has mentioned an Arduino workaround for this.

This has been working fine for five years.

But now, the rear tank runs dry seemingly at a random mileage between 120-150.

At first it thought it was because I'm pushing the truck so hard, or my speedo/odo was dying.

So I've been using Google maps to follow miles and check speed.

BUT when filling up I can only get 13-17 gallons into the tank.

I can see the fuel in the fill neck, so I know it's full.

If it was consistent, I would say the pickup had fallen off.

I can leave the gas cap loose and it still happens, so not a vacuum problem.

Tanks are fairly new, and clean according to borescope inspection. (Dont send a cheap $15 cellphone borescope into whatever they call gasoline these days )

Hard to imagine there's a random 2-6 gallons of water in there,and I didn't see any phase separation with the scope, but my next 'experiment' is to dump a couple of gallons of toluene in with my next fill up.

That's miscable with water and pretty difficult to separate.

It will burn in its equilibrium state and has a good octane #.

Can anyone see something I'm missing?

Any other ideas to fix or figure this out?

Hijack/

 

[Rembrant]

I don't "know", but I'd think that the pickup tube should be almost to the bottom of the tank. Otherwise the water at the bottom of the tank can't be used.

FIFY...

I hope this hijack isn't inappropriate, but I want to say that I changed both tanks and senders about four years ago.

I could not find the one year wonder '87 senders, so I went with '86 mechanical pump senders.

These read completely wrong, so I've been just watching mileage with fill ups and figure I need gas around 160 miles per 19 gallon tank.

Gary has mentioned an Arduino workaround for this.

This has been working fine for five years.

But now, the rear tank runs dry seemingly at a random mileage between 120-150.

At first it thought it was because I'm pushing the truck so hard, or my speedo/odo was dying.

So I've been using Google maps to follow miles and check speed.

BUT when filling up I can only get 13-17 gallons into the tank.

I can see the fuel in the fill neck, so I know it's full.

If it was consistent, I would say the pickup had fallen off.

I can leave the gas cap loose and it still happens, so not a vacuum problem.

Tanks are fairly new, and clean according to borescope inspection. (Dont send a cheap $15 cellphone borescope into whatever they call gasoline these days )

Hard to imagine there's a random 2-6 gallons of water in there,and I didn't see any phase separation with the scope, but my next 'experiment' is to dump a couple of gallons of toluene in with my next fill up.

That's miscable with water and pretty difficult to separate.

It will burn in its equilibrium state and has a good octane #.

Can anyone see something I'm missing?

Any other ideas to fix or figure this out?

Hijack/

How much does the rear tank hold? Or, how much is it supposed to hold?

[ArdWrknTrk]

How much does the rear tank hold? Or, how much is it supposed to hold?

Cory, i have 19 gallon tanks both side and rear.

At 160 indicated miles I used to fit around 18.3 gallons, and I hadn't run it dry.

Now it 'runs dry' when it feels like it.

Hopefully while I'm rolling, not stuck in traffic, as it takes a lot of cranking to prime the pump.

I now have to remain vigilant to the hint of starvation, since it is so random

[Gary Lewis]

Cory, i have 19 gallon tanks both side and rear.

At 160 indicated miles I used to fit around 18.3 gallons, and I hadn't run it dry.

Now it 'runs dry' when it feels like it.

Hopefully while I'm rolling, not stuck in traffic, as it takes a lot of cranking to prime the pump.

I now have to remain vigilant to the hint of starvation, since it is so random

You said you went with '86 mechanical pump senders. Does that mean you either have a mechanical pump or a frame-mounted electric pump. If so I'll guess that you have a bad hose that's leaking at times, perhaps as the body twists, and allowing air into the system and killing the vacuum the pump is creating.

But yours should have the plastic hose, and they don't seem to age. Maybe a connection is leaking or loose?

[ArdWrknTrk]

You said you went with '86 mechanical pump senders. Does that mean you either have a mechanical pump or a frame-mounted electric pump. If so I'll guess that you have a bad hose that's leaking at times, perhaps as the body twists, and allowing air into the system and killing the vacuum the pump is creating.

But yours should have the plastic hose, and they don't seem to age. Maybe a connection is leaking or loose?

I have a pump on the timing case.(two pin connector on the bung)

There are no fuel line leaks, and the switch valve is good.

It ONLY does it towards the bottom of the tank, not randomly.(but at a random fill level)

The senders look 'new' when I scoped it.

I don't see, nor could I understand a hole in the pickup tube.

Because one day it will take 13, and the next 17, but never the full 19 like it did before (if I ran the tank dry)

[Gary Lewis]

I have a pump on the timing case.(two pin connector on the bung)

There are no fuel line leaks, and the switch valve is good.

It ONLY does it towards the bottom of the tank, not randomly.(but at a random fill level)

The senders look 'new' when I scoped it.

I don't see, nor could I understand a hole in the pickup tube.

Because one day it will take 13, and the next 17, but never the full 19 like it did before (if I ran the tank dry)

You have it in the right thread - weird!