Unmolested 1971 EEC system??? - If it matters, 402/400TH with A/C

[71CHEVYSHORTBED402]

Finding it somewhat difficult determining the factory EEC configuration for my 71/402/AC project truck. I'll be reconnecting it with the rebuild.

For what it's worth, the story is I bought this truck in 89 with 90K miles. Other than paint & a missing stove pipe, to my knowledge the truck was truly "unmolested" less unseen repairs, which there couldn't have been many.

In 1993 we R/Rd' the engine rebuild and removed the vapor canister & A/C. If I recall, the A/C was working less a possible charge. At the time we installed a valve on the end of the vapor line. I can't say if the vapor canister was connected per factory, but if I had to guess it was.

Unless I'm off me rocker (quite possible), since then the vapor line has been connected to the fuel pump. Can't say for certain, because I often used a mechanic (oooops, wasn't raised around a wrench).......I think the original fuel pump was a single port from the tank, and since then it was replaced with a dual port pump for a return line.


Anyway, some questions please & appreciate any responses. The first image is how I found my fuel tank. It's consistent with the second image below (for A/C, non-A/C, both?)..............Course there may be factory variances.

1. I was informed because this is an A/C truck the sending unit should have had two lines to minimize vapor lock. My other truck (72 A/C) has a dual line fuel sender, but the vapor assembly and canister was removed. That and the tank is unlike my 71.............Anyway, if the sending unit is supposed to have two lines, I'm assuming both run through the cab floor. Beings there are just two holes in the cab floor, can you describe how the tank is connected to the vapor canister?

2. On the flip side, I'd be a bit surprised to learn my sending unit had been replaced at some point. That and by the looks of the filter sock (yikes). My gut says the fuel sender is correct for this truck (doesn't mean it is). To me that would mean there was never a return line. One 3/8" line was run from the tank to the fuel pump, & one 5/16" line was run from the tank to the vapor canister.

My 1971:



Matches this (A/C, non-A/C, both?)

[FirstOwner69]

DAMN, I'm glad they didn't use this crap in 1969!

[71CHEVYSHORTBED402]

Originally Posted by FirstOwner69

DAMN, I'm glad they didn't use this crap in 1969!

No doubt!..........I think it all started in 70. Obviously I don't need to hook it up, but I'd like to just cuz.

I still say someone can earn some cash with a repro. canister. Most GMs used the same can.

[dfwright]

So mine is a '72, NON-AC truck. I have 2 lines from the sender. I believe one is the feed, and one is for return from the fuel pump. I can post other pictures of where all the lines actually run if you need.

[71CHEVYSHORTBED402]

Originally Posted by dfwright

So mine is a '72, NON-AC truck. I have 2 lines from the sender. I believe one is the feed, and one is for return from the fuel pump. I can post other pictures of where all the lines actually run if you need.

Very cool. Looks like mine only two lines that run through the same hole, and the other hole for vent. Other pics aren't necessary, I know where that vent line is going. Hmmm, non-A/C..............I suspect there were variances. Anyone have an EEC A/C truck without a return line per factory?

Thanks for the response.

[davepl]

Mine's a 70 '402 but it's a C2500 (C20) - is that why it's lacking these I wonder? Or is it because it's a year older?

[71CHEVYSHORTBED402]

As I drill down, perhaps as verification of a single line sending unit (no return)............ There are quite a few variances for sending units. http://www.gmpartswiki.com/getpage?pageid=21463. Here's what I found on parts WIKI for 71 C-10. All single line sending units. A few of these probably don't apply:

67-72 6428272 Service 10 (D-D) Meter assm. W gasket Single Line Sender: Don't know anything about vans, but does this mean service 10 van only, or service 10 & van?

68-71 6428271 Service 10-20 (single unit) (327, 350, 396) Meter assm. W gasket Single Line Sender: 3/8" line.

69-71 6428361 Service 10-30 - W/4BC -350, 396, 400 Meter assm. W gasket Single Line Sender: I believe 4BC means four barrel carb. Looks to be the correct sender for my 71 402 4BC. 3/8" line.

70-72 6428850 Fleetside Meter assm. Aux. Fuel Tank Single Line Sender: Looks to be for an aux. tank. Unsure of configuration.

[71CHEVYSHORTBED402]

Originally Posted by davepl

Mine's a 70 '402 but it's a C2500 (C20) - is that why it's lacking these I wonder? Or is it because it's a year older?

Probably because it's a year older. I believe they began using these in 70-71. There's not much under parts WIKI. The oldest can I'm aware of drills down to a 1970 Chevelle & 1971 Nova/Chevelle/Camero

Edit: The parts wiki search engine doesn't always work. I found this though. By the looks of it the EEC systems began in 1970. Variances may have to do with state regulations, similar to what I think applies to coolant expansion tanks: http://www.gmpartswiki.com/getpage?pageid=21464

EDIT: I didn't want to bump this thread, but if interested, see post #7 here. Couple parts relative to some trucks. There are variances. Some dual line senders/pumps, some single. From my angle EEC nor A/C has anything to do with it: http://67-72chevytrucks.com/vboard/s...d.php?t=737266