Im having trouble figuring out what fuel tank and sending unit to buy for my '84 T/A, the problem is that ive heard on the forums that the H.O. L69 had a mechanical AND an in tank fuel pump helper, looking at the fuses this seems to be the case since I have one in "F. Pump", but seemingly no connector/clip above the gas tank that ive seen in the later F.I. years.


Fuse-box

Directly beneath fuel-tank/diff looking up

Im redoing my entire rear suspension soon, so I thought it'd be best to knock this out of the way now since my fuel gauge doesnt accurately read level and everything I need to remove would be gone at that point.

Thanks!

 

The power/sender harness comes from near the tail lights on the driver side. The harness goes along the frame and up the tank. The 82-83 efi cars I think actually shared a ground or power wire w the tail light harness. Idk about the HO cars but the harness is in the same place, so more on the back side of the tank. It's totally different than the 85- up bulkhead style.

 

Most of the HO cars don't have the electric pump until later years than 84. Seems to me it was only a dealer-installed hack-around to stifle customer complaints in 84.

Look at your gas tank harness. If memory serves, the gauge wire is pink. There's probably a ground wire there also which would be black. If there aren't any other wires you don't have an in-tank fuel pump. The wire for that in EFI cars was tan/wht if memory serves even more; no idea whether the dealer-installed thing would have been the same color.

Odds are also, if you don't have the EEEEEEZZZZZZZZY hack-around in your car, which was a stuuupid little goofy fan mounted on the driver's side strut tower and blowing on the carb, you probably don't have the HARD one (the pump) either.

 

I never knew about the fan fix, that is goofy

Anyways, I finally got the time to check out the harness and I found it running back to the tail-lights.



I know its not all that clear to make out, but it definitely does have the tan/white wire in addition to the pink and black, so should I buy something like this for the sending unit?

https://eclassics.com/eclassics-1982...caAucEEALw_wcB

Also, what fuel tank should I buy to match it?

 

I used a specter tank. It fit well but the filler neck needed a little "manipulation" to sit centered in the filler door. I'd drop the tank and check it out. The inside of my 82 tanks was perfect. I didn't need a new one but had one sitting so I used it.


that sender is for efi/an electric pump. It would probably work as long as you have an in tank pump which it looks like you have.

Gm put a little fan blowing on the carb! WTF! That's a **** poor fix. I thought ford sucked cause the electronics in my f350 glitch out all the time, they sent out a recall saying they're aware of the issue and don't know what to do! Maybe they need a little fan blowing on the infotainment system!

 

Check to see if that tan wire is hooked to anything. They may have included it in the loom in all cars and just not used it when not needed.

 

Its hard to tell without dropping the tank entirely, but I definitely see it running along the harness to the top of the sending unit along with the pink and black wires.



Hard to get a good picture, but shortly after its no longer visible they all three take a 90° turn upwards into where the center of the tank would be.

Not exactly "concrete evidence", but is it safe to say ill need a 3-pin fuel sending unit since the one in it currently is?

 

So, I agree w sofa, the factory often puts unused wires in the harness. That said. My lg4 82 had only 2 wires. I had an 83ho I parted out and used the rear wiring harness, it didn't have the fuel pump wire either (or a little fan in the engine comp!). But you're not gonna know till you drop it.


but, if you have an in place fuse and the wire, I'd put money on a pump too!

one thing I never understood is the pressure the pump puts out, is it the same as a crossfire pump? I'm aware it's more of a helper pump for the block mounted mech pump.

 

I wanna say they're two separate pumps, the helper should be only around ~3psi while the cross-fire pumped around ~12psi (?).

Ill start the process on dropping my tank later today, we'll see

 

Right: the carb "helper" pump only put a tweeeek of pressure in the line to help keep the fuel in it from flashing into vapor as it passed through hot places. I kinda don't think they had those in 84 though.

 

I have found the helper pump factory installed on two '84 model L69s: a 12/83 build and 2/84.The pump is about 1/2 the power of a CFI pump and may be from the Vega parts bin -single stage turbine and no check valve.

 

kinda a moot question though since the sender for the carb vehicles WITHOUT fuel pumps are no longer available

easy enough to modify the fuel pump sender WITH PUMP though by cutting off the fuel pump bracket and installing an extension for the fuel pickup line

pretty common practice here, a search should show some examples

 

I believe they are available now, at a hefty price...

 

One of my 84 L69 had it and the other did not. The one with the pump had 3 wires going to the gas tank the other 2

 

I didn't find one available last year at the standard parts establishments. I did not look at ebay, I try to stay away from there for parts that may need to be returned.

the sock for the non-pump sender was not widely available either and I paid around $20 for one. I can imagine what the non-pump sender may cost now if you can find it

modification of the fuel PUMP sender is simple enough with a fuel line repair kit and a little rewiring- you'll need to remove one lead and solder your two wire plug in place of the 3 wire.

hold onto your old one so you know how long to lengthen the suction line.

 

UPDATE: Sorry gents, ive had quite the busy life these past few months, but I was finally able to drop the tank (among other things) and...

There's a fuel pump!



Or rather whats left of one, im genuinely surprised this thing ran at all after seeing the state of it.

Tomorrow I should be receiving all that I need to get her back on the road, I know my cars a rare case but ill pop back in to verify the parts I have worked and list the part numbers if anyone ever needs to do the same in the future.

 

Oh, and one last thing.

My Carter M6626 mech. pump has a built in return line, but ive gone about purchasing a bypass style fuel regulator just to make sure both pumps wont overwhelm the carb, as of now I have it plumbed to block off the return line on the mech. pump and use the regulators return, but does this setup work to begin with?




Or is it better to just swap back to the steel hard straight from the mech. pump to the carb and ditch the regulator entirely?

 

best to let the fuel circulate through the mechanical pump then to the return as the factory plumbing intended

if you have the correct in-tank pump installed, it should put out no more than 2 or 3 PSI

I imagine however that there's a non-zero probability of getting a TPI pump, or some such other, with the fuel sending unit when purchased today

probably worth checking the actual pump model number if possible before installing.

 

It went even better then I thought it would!

I'll list all the parts used below and a few notes on what I had to modify/change for my application.

CARTER M6626 - Mech. Pump -
*Old one worked well, but theyre cheap so might as well
MOTORAD MGC822 - Fuel Tank Cap

SPECTRA PREMIUM GM2721B - Fuel Tank
*The main fuel feed line had an inverted flare nut as opposed to a standard hose fitting, I had to trim the lip of the end to allow the 3/8" hose to fit over it.
SPECTRA PREMIUM ST23 - Fuel Tank Straps

CARTER STS4 - In-Tank Fuel Pump Strainer

https://a.co/d/hI4Va2T - Fuel Tank Vent Valve
*Legitimately couldn't find it anywhere other then Hawks Motorsports and Amazon
CARTER P90070 - In-Tank Fuel Pump
*Biggest thing of note, this came in the later 1987+ H.O. firebirds that had a mechanical pump and a helper unit, I cross referenced this pump with the one that came out of my old tank, theyre functionally identical and you only need to modify the sending units connectors.
SPECTRA PREMIUM FG20A - Sending Unit
*See note above, other thing of note is my Trans Am came with a 3-pin connection already, my harness code is FEH as pictured earlier in these posts, otherwise functionally identical and displays fuel accurately, primes fuel pump, etc. Only necessary change for me was lengthening the harness to ~45in from the pigtail to make it long enough to reach the connector.




Note: Pic taken before lengthening connector pigtail

Since getting everything bolted back together, I can tell a SIGNIFICANT improvement, not only does the car start right up (and my gas gauge works finally), but it has a significantly snappier throttle.

Thanks for reading!

 

This is good information to know.

Quick question though. Where did that short piece of rubber fuel hose you used to connect the fuel pump outlet to the fuel supply line come from?

That piece of fuel hose MUST be rated for constant submersion in gasoline. It's a special fuel hose and it's expensive. Like $25.00 a foot.

If it's not that special fuel hose it will turn to goo, and you will be dropping the tank and doing it all over again.

 

I ended up going with what should be SAE J30R10 hose, but the more I think about it the more im starting to doubt it...

As easy as an access panel is, ive already done it once so I guess I can drop the tank again...

 

Checked the receipts... it was SAE J30R9...

Time to run it back

 

Sorry man.

Better to find out now than a year later and wonder why your car is acting funny while you beat your head against a wall trying to figure out what's up.

 

Its fine, you live and learn I suppose

Genuinely thank you for the heads up on that though, it absolutely would have flown right over my head until it became an issue down the road like you said.

 

Great video explaining about fuel hoses. Helpful for others that might come across this thread later on.

 

Definitely a good video to watch.

Got it all done in just shy of ~2 hours, that hose absolutely would not have lasted, felt like a stress ball when I got it out.

 

Glad you got it caught now rather than later on.

It's still fresh on your mind taking everything apart and putting it back together and you probably didn't even have all your tools put up yet from doing it the first time.

I actually was researching doing this for some other members on here facing the same problem. The parts I came up with were more or less the same as the ones you used. I noticed the Carter 3 PSI helper fuel pump was shorter than the TBI or TPI electric fuel pump that would normally be used with the Spectra fuel pump hanger/sending unit, and it would need a longer piece of the special submersion rated fuel hose to make it work.

I saw your picture with the assembled unit on your workbench with the length of fuel hose laying to the side next to your hose cutters. I thought to myself "I wonder if he used a piece of that special hose or not?".

So, I decided to ask you if you did.