Replacing all fuel lines, 88 RCSB TBI 4.3L

[DeCaff2007]

I'm confused.....where is the problem?

4.3 uses a different size return line, 5/16" iirc.
kit appears to be for a 5.7, does the 5.7 use 3/8 or 5/16?

also check out lines to go, linestogo.com, quality stuff.

The kit was advertised for a 5.7L. I have a 4.3L The question was whether or not the return line was going to be the correct size. The sellers Ebay page advertised the fuel lines to fit a 4.3L all the way up to a 6.0.

Luckily, the return line is the correct size.

 

[454cid]

I don't believe the lines are engine displacement dependent. Even my 454 uses a 3/8" line for the supply, a 5/16" for the return, and a 1/4" for the vent line. The only lines I'd expect to be different would be for the diesel, or year differences for connection changes....later trucks like mine use quick connect fittings.

I think those sizes have been a GM standard for quite some time, as I think my 69 Buicks are the same.

 

[DeCaff2007]

A 69 Buick, eh? What model? My Wife has a 67 Buick Special Deluxe... it has 1 fuel line from the tank to the pump. 1 fuel line from the pump to the carburetor. No return lines, although the line from tank to pump is 3/8ths. The line from the pump to the carburetor is 5/16ths.

Nevermind... just read the Buicks in your sig. I favor the LeSabre.

 

[454cid]

A 69 Buick, eh? What model? My Wife has a 67 Buick Special Deluxe... it has 1 fuel line from the tank to the pump. 1 fuel line from the pump to the carburetor. No return lines, although the line from tank to pump is 3/8ths. The line from the pump to the carburetor is 5/16ths.

Nevermind... just read the Buicks in your sig. I favor the LeSabre.

Yeah, some of them were plumbed that way....might be non-ac cars?

 

[Schurkey]

Generally, the old cars with engine-driven fuel pumps and A/C would get a 1/4" vapor return tube back to the tank from the fuel pump; restricted at the pump to ~.060 or smaller. Passed vapor easily, but cut down on the amount of liquid fuel going back to the tank.

 

[DeCaff2007]

You're both correct. My Wife's non A/C Buick has no return line, nor that 1/4" vapor line. I still don't understand why A/C has anything to do with fuel return and vapor lines.

My 76 Trans Am, however, was equipped with A/C from the factory.... and indeed has both a return and vapor line.

Ironically, my 88 RCSB does have the return and vapor lines. No A/C. It does, however, have A.I.R. and a smog pump. Maybe that's why there's three steel lines running up the driver side frame... (Actually, there's four. One is a brake line lol).

 

[Nad_Yvalhosert]

On the fuel injected trucks, SUV's, etc, all gasoline engines, 6 or 8 cyl, used 3/8" pressure, 5/16" return, and 1/4" vapor lines from 88-98. Regardless of horsepower, or injection design (TBI or Vortec). The shapes and lengths changed based on wheelbase, tank location, and connector. But the sizes stayed the same.

 

[Schurkey]

You're both correct. My Wife's non A/C Buick has no return line, nor that 1/4" vapor line.

Huh? The vapor return should be the ONLY return. Are you sure the extra tube you're looking at goes to the fuel pump? I'm thinking maybe fuel tank vent to the charcoal canister.

I still don't understand why A/C has anything to do with fuel return and vapor lines.

Added heat load in the engine compartment, makes the vehicle prone to vapor lock. The vapor return reduces the chances of vapor-locking the pump.

My 76 Trans Am, however, was equipped with A/C from the factory.... and indeed has both a return and vapor line.

Ironically, my 88 RCSB does have the return and vapor lines. No A/C. It does, however, have A.I.R. and a smog pump. Maybe that's why there's three steel lines running up the driver side frame... (Actually, there's four. One is a brake line lol).

Again, there should only be one, 1/4" vapor return. There's no "liquid" fuel return except what blows down the vapor-return tube unintentionally.

Are you CERTAIN that there's four tubes screwed to the fuel pump--Fuel inlet (suction), fuel outlet (pressure to carb), vapor return, and some other "return"?

 

[454cid]

Huh? The vapor return should be the ONLY return. Are you sure the extra tube you're looking at goes to the fuel pump? I'm thinking maybe fuel tank vent to the charcoal canister.

I don't have a charcoal canister on either of my 69 Buicks, unless it's under the car near the gas tank like a GMT-800, but I don't think that's the case. Buick used 2 and 3 port fuel pumps. There has to be a supply (from the tank) and a carb feed..... I guess I don't really know what the extra line is for. I was thinking 3 ports = 3 lines, but then the carb would get nothing I think I only have two lines running along the frame, now that I think about it.... so not exactly like my truck.

Added heat load in the engine compartment, makes the vehicle prone to vapor lock. The vapor return reduces the chances of vapor-locking the pump.

Thanks, I wondered about that too.

 

[DeCaff2007]

Huh? The vapor return should be the ONLY return. Are you sure the extra tube you're looking at goes to the fuel pump? I'm thinking maybe fuel tank vent to the charcoal canister.


Added heat load in the engine compartment, makes the vehicle prone to vapor lock. The vapor return reduces the chances of vapor-locking the pump.


Again, there should only be one, 1/4" vapor return. There's no "liquid" fuel return except what blows down the vapor-return tube unintentionally.

Are you CERTAIN that there's four tubes screwed to the fuel pump--Fuel inlet (suction), fuel outlet (pressure to carb), vapor return, and some other "return"?

On which vehicle?