Goofy Gas Gauge or Pesky Space Aliens!!

[mtnmankev]

Okay, it did it again today.
I swapped the gas caps, topped off the tanks and went to Flagstaff today.
On the way home, got about 20 miles out of Flagstaff and the engine started sputtering so I switched over to the passenger tank and drove home without issue.
Stopped along the way home where gas was the cheapest and topped off the main tank i drove on initially today and it only took 8.57 gallons to refill it.
This is becoming a mind teaser .......
I'm rapidly running out of ideas what to check.

 

[DoubleDingo]

Very interesting. I head scratcher indeed. Swapping caps didn't help, it bogs at the same place each time, switching to the passenger tank gets you back up and running, all the while the driver's side tank is still half full of fuel. Not vapor lock, perhaps it's the fuel lines themselves collapsing. If you haven't replaced the old ones, it may be your culprit. Get some high grade fuel injection hose and replace the old rubber lines, it may be the vacuum from the pump collapsing the old lines on that side. In my old Mean Green, it had dual tanks, steel or copper lines plumbed to the manual diverter valve, and hard line up to the pump. On the side tank, going down the road, I knew when it was running dry because it would make a thunk sound from the tank being drawn in from the vacuum. If I kept running it on that tank it would run out soon after, so on trips I would fill both tanks and start the trip on the side tank so I knew when it was dry from that thunk sound it made, then I'd switch it over to the saddle tank and knew I had another few hours of drive time before a fuel stop was needed. These trucks having rubber lines plumbed from the tanks and everywhere else, you may just have some old rubber that collapses easily.

And yes, Indian spirits do exist. Have heard some crazy stories from guys that work at a geothermal plant that is built on old Indian land, not a burial ground, just the land.

 

[mtnmankev]

I know the rubber lines from the passenger tank leak, and want to replace them.
I am going to buy some 2x4's on payday so I can build a framework and remove the truck bed to access the lines and I will replace ALL of them and thank you for the injection line suggestion.
Maybe the ethanol gas won't affect them as much as rubber.

I watch a LOT of Ghost Adventures so I can relate to what they investigate, along with personal experiences.
The area I live in has always been populated by native Americans, I have found a couple dozen arrowheads on my 1.6 acres alone.
I got a copy of They Live dvd from the library today, so I am probably going to see if I can locate and order a pair of the special sunglasses so i can ID the aliens living here.

 

[Snoots]

I've been probed.

Without photos, it didn't happen.

 

[mtnmankev]

For the time being, I will live with the goofy gas gauge until I can pull the truck bed and go over everything.

But I DID find the running out of gas problem, and it's surprising.
It IS vapor lock despite the spacing from the exhaust pipe to everything else.
It's amazing the amount of heat under the truck, more than I have ever felt from any other vehicle I have owned.

I will have to get a custom made exhaust system that will end up being at least 4 inches lower than it currently is, and then I won't drive through dry grass for fear of starting a wildfire, plus I will have to fabricate some heat shields to try and keep the heat from getting close to the fuel lines.

 

[75gmck25]

When you buy new fuel lines, go online and order SAE 30R9 (high pressure) or SAE 30R7 (low pressure) rubber fuel injection hose. It is designed to hold up to modern fuels with ethanol.

Most local parts stores also stock this hose, but its going to be several dollars per foot in the store. It won't be a lot cheaper online, but I found some places where I could get a little price break. I also used fuel injection hose clamps that provide full circle clamping without pinching the rubber.

Bruce

 

[bucket]

When you buy new fuel lines, go online and order SAE 30R9 (high pressure) or SAE 30R7 (low pressure) rubber fuel injection hose. It is designed to hold up to modern fuels with ethanol.

Most local parts stores also stock this hose, but its going to be several dollars per foot in the store. It won't be a lot cheaper online, but I found some places where I could get a little price break. I also used fuel injection hose clamps that provide full circle clamping without pinching the rubber.

Bruce

Do you prefer a specific brand of fuel injection hose clamps? It seems like every single one I've used was garbage and I've always preferred worm clamps because of it.

 

[Blue Ox]

For the time being, I will live with the goofy gas gauge until I can pull the truck bed and go over everything.

But I DID find the running out of gas problem, and it's surprising.
It IS vapor lock despite the spacing from the exhaust pipe to everything else.
It's amazing the amount of heat under the truck, more than I have ever felt from any other vehicle I have owned.

I will have to get a custom made exhaust system that will end up being at least 4 inches lower than it currently is, and then I won't drive through dry grass for fear of starting a wildfire, plus I will have to fabricate some heat shields to try and keep the heat from getting close to the fuel lines.

If it's getting that hot under there is it possible you have some other issue, like a mixture problem that's causing the exhaust to be so hot? Do you have cats?

It doesn't make a lot of sense that the factory plumbing and exhaust has this problem. GM usually knows to look for these things, and if it was an issue one would think they would have solved it over the course of 15 million units.

 

[mtnmankev]

No cats.
But it is a dual system made up from what I had on hand, so it will be different from factory, but I tried to space everything away from the frame and cross rails but not drag on the ground.
Often I see exhaust systems tucked up not far from the body and they seem to do fine, mine is actually a ways lower and i feel it needs to be farther down yet for air circulation.
I adjusted the Q-jet turning the screws out just to max rpm at idle, then back in just a hair.
Also have a problem with heat soak in the starter, after a good highway run the starter is so hot the truck will not crank until the starter cools.
It did it before when it had headers and it still does it with stock manifolds.
I am about at my wit's end ...

 

[Albrigap]

I fixed the dual tank and one gauge problem.
I pulled the needle off the gauge and then took out the rivets holding the gauge to the plate.
I done the same to a second gauge so I had two gauges and one plate.
I then repainted the gauge disk black.
I then drilled holes mounting the gauge units side by side on the face.
I then used the short amp gauge needles on each gauge unit.
I used model railroad stickers to put the E/F on both gauges.
I had to run one wire to the switching valve to get the gauge reading to the second gauge unit.
This worked great.
I now have separate gauges for each tank.
The valve switch works as it should.
To know what tank you are on, look at the switch.
Now I do not run one tank dry, switch over only to find that one dry too.
This is on a 1981 C10 6.2 diesel.