Bad gas is downright offensive. It can cause 4x4 owners and their passengers to gag. Under extreme circumstances, bad gas can even be lethal. Over-the-counter remedies can relieve intestinal gas problems, but vehicular gas problems can't be solved with pills or pink liquid.
We found this out the hard way on a '77 Chevy 3/4-ton. The vehicle sits during the week, its gas tank sweating with condensation. Crud accrued over the years. Stalling intervals were extended by siphoning out the tank and by changing the fuel filter frequently. However, pulling the fuel filter to limp a half-mile home proved to be the last straw, plugging Quadrajet orifices. The resulting rich condition emitted enough tailpipe carbon monoxide to make everyone within 10 feet nauseated. Emissions-testing classified it a gross-polluter.
Gunk is us. Rust and corrosion...
Gunk is us. Rust and corrosion from a 30-plus-year-old gas tank entered the fuel system through an equally old sender, complete with a decomposed filter sock. LMC Truck is one-stop shopping for popular American truck replacement parts. Shown below is their repro gas tank, mounting kit, prebent lines, hardware, and fuel pump made for a complete pre-carburetor system revival. A Proform fuel filter is also shown.
Rehab or Replace?
Always looking for the cheapest fix, we checked into professionally cleaning the old gas tank, which didn't have any external signs of rust. Research revealed that California toxic-waste regulations now keep the average radiator shop from performing gas-tank service. The procedure's cost at the closest (far-away) place led to Plan B.
Legendary driveway mechanics mentioned at-home cleaning by pouring pea gravel into the tank and shaking vigorously to bead-blast the corrosion loose. Then the tank could be internally revived with fancy swish-around sealer from an auto-restoration specialist. Our issues with this were where to dispose of toxic rocks (small kids and curious pets on the premises) and how to thoroughly rinse out the tank. On to Plan C.
For popular trucks, replacing the tank can actually be cheaper than resurrecting the original one. Unless you're into hyper-anal 100-point OE car shows, a repro tank is a viable solution. Even rustproof polyethylene replacement tanks can be somewhat affordable, depending on the vehicle.
Since the OE fuel lines are also steel and prone to internal corrosion, it makes sense to replace them too. (OE-contour stainless lines are even available from aftermarket specialists.) We verified this hunch by running the new tank behind the old lines. The fuel filter eventually plugged. For good measure, we obtained a new Carter fuel pump to replace the existing one (vintage unknown). LMC Truck is a comprehensive source for replacement Chevy truck parts.
| LMC TRUCK PARTS LIST (’77 CHEVY K20) |
| 32-5930 | 20-gal side-mount gas tank | $119.95 |
| 32-5820 | gas tank strap set | $29.95 |
| 32-5816 | gas tank antisqueak kit | $9.95 |
| 32-4034 | sending unit (2-outlet) | $69.95 |
| 30-1290 | sending unit lock ring with O-ring | $8.95 |
| 32-3650 | main fuel line | $79.95 |
| 32-3676 | pump-to-carb line (Quadrajet) | $24.95 |
| 32-3654 | vapor line | $79.95 |
| 30-1746 | fuel line clips | $26.95 |
| 32-4728 | fuel pump | $24.95 |
| 32-4620 | fuel pump pushrod | $9.95 |
1. Use the proverbial Oklahoma...
1. Use the proverbial Oklahoma credit card to give the old tank a high colonic before removing it. Check local ordinances for approved toxic-waste disposal. Unclamp or cut the filler, vent, and sender hoses depending on their condition. Four bolts hold each of the saddle-mount tank's two straps to the frame.
2. The shiny new tank is prepped...
2. The shiny new tank is prepped by wrapping antisqueak material under the mounting straps and installing the sending unit. Our old straps were in reusable condition. Gluttons for punishment, we removed the old lines like a surgeon extracting intestinal tapeworms. Instead of snipping them, we wanted to prerun the line routing.
3. The LMC replacement lines...
3. The LMC replacement lines have shipping bends with tags indicating where the tubing needs to be stretched. Straightness isn't critical-the lines will get tweaked during installation.
4. Leave the shipping caps...
4. Leave the shipping caps on while threading the new lines along the frame through the crossmembers. Secure in the OE locations (the area under the motor mount can be challenging) to protect against cracking. Uncap and blow out the new lines, then use new fuel hose for the necessary connections. (The bypassed dual-tank valve is visible at the top of the photo.)
5. We spliced an auxiliary...
5. We spliced an auxiliary Proform 2-stage inline fuel filter into the hose between the main line and new fuel pump. This provides 50- and 30-micron filtration plus easy contamination inspection upstream of the primary Quadrajet filter.
Installation Insights
* Have a helper. Rent a "friend" if necessary to expedite tank R&R and line-routing. Also, fuel pump replacement is challenging at best without a second pair of hands to insert the pushrod.
* Empty the existing tank as much as possible using a siphon that doesn't require mouth suction.
* Use a floorjack and a piece of plywood to support the tank if attempting a DIY/friendless installation.
* Capture and dispose of old gas appropriately.
* Even though many legendary fuel-system gurus smoke while working, they're apparently trained professionals, not mere mortals. Along the same lines, resist the temptation to apply flame to corroded fuel fittings.
* Instead of applying flame, spray all existing fittings and fasteners with penetrating lubricant to ease their removal.
* A 5/8-inch line wrench should be used on the fuel-pump-to-carb line's fittings on older Chevys.
* Any fuel debris in the carburetor means it'll need to be rebuilt or replaced.
* The photos and captions provide more details on solving the truck equivalent of irritable bowel syndrome. (Drivers and passengers are on their own to solve any personal gastric issues.)