1977 K10 fuel sender questions

[3x2GTO]

I'm replacing the gas tank on my 77 K10, and noticed it has a 2 port sending unit ( it also needs replaced) the 2nd port is plugged with piece of fuel hose with a bolt stuck in the end. Can I just run a single port sending unit?

[cadillac_al]

I would go with a 3 port sending unit. Then you get the return line and a nice vent line to use the old style plastic vent.

[3x2GTO]

I'll check my pump to see if it has a return on it. Old style plastic vent, something like a differential vent?

[Dead Parrot]

The mid 70's squares with what was called "Heavy Duty Emissions" often used the no-return fuel pump and the over the tank vent. There should be a SPID entry to that effect. Usually has a max gross weight of 6200lbs. Guessing yours does not have or ever had a charcoal canister?

As for the vent, yes it is the same as a differential vent that has a loose cap.

[3x2GTO]

Aluminum tag on the door jamb GVWR 6200lbs, 10 x 15B 30 PSI, Camper instructions, 3520lb front, 3520 lb rear, no evidence of a charcoal cannister, fuel pump has no return, SPID has nothing about emissions on it. It's a short bed K10.

[cadillac_al]

I like to use the return when available but I probably wouldn't plumb one back there if it didn't come with one. I guess the 2 port sender is all you need. Don't plug the vent though, use a diff vent.

[3x2GTO]

Thanks for the info! I'll use a 2 port and run a diff vent cap.

[Dead Parrot]

I double checked my SPID. The Heavy Duty code was a F44 for Heavy Duty Chassis. In 75 that avoided Cats, air pump, EGR and such and your fuel gauge just read Fuel instead of Unleaded Fuel.

The vent cap may have disintegrated due to age and a PO replaced with bolt and then used a vented gas cap for a vent. The OEM cap is non-vented. Or possible the rubber hoses from the fill port to the gas tank now have venting due to cracks.

[3x2GTO]

Only HD on my SPID is F60 for springs, my gas gauge reads unleaded fuel only, the truck was originally a stepside, but bed has been replaced with a fleetside one, and has the original gas cap for the fleetside. The gas lines are old and cracking, very possible it's venting through those or elsewhere. Thanks for the info.

[wazzabie]

Originally Posted by 3x2GTO

Only HD on my SPID is F60 for springs, my gas gauge reads unleaded fuel only, the truck was originally a stepside, but bed has been replaced with a fleetside one, and has the original gas cap for the fleetside. The gas lines are old and cracking, very possible it's venting through those or elsewhere. Thanks for the info.

I know on an original 78 K5 Blazer w/ federal emission and the HD F60 springs the fuel gauge does not read unleaded fuel only. Does your PID show federal emissions? I think federal emissions is the same as heavy duty emissions.

[3x2GTO]

No, there's no mention of any kind of emissions on the SPID. I dropped the old tank today, turns out what I thought was a bolt plugging off the vent hose was actually an old style vent cap ( like a differential one), there was so much caked on grease that it was hard to tell what was what. The old tank was actually a Spectra Premium replacement that just started to weep, my new one will be here tomorrow from Summit, but now I'll have to order new braces and straps and sending unit.

[wazzabie]

Originally Posted by 3x2GTO

No, there's no mention of any kind of emissions on the SPID. I dropped the old tank today, turns out what I thought was a bolt plugging off the vent hose was actually an old style vent cap ( like a differential one), there was so much caked on grease that it was hard to tell what was what. The old tank was actually a Spectra Premium replacement that just started to weep, my new one will be here tomorrow from Summit, but now I'll have to order new braces and straps and sending unit.

Did you have any rust in your tank?

[3x2GTO]

I didn't check the insides, the bottom was soft and leaking, so I'm sure it did.