How many lines, 2 or 3 on stock 85 SS fuel sending unit? Every where I look 2 or 3 lines are listed, I would like to have the right one on hand before dropping the tank to replace mine.

Not sure if it's the same as an 88 ss but mine has a supply, a return, and a vent.

Should be a three line unit. A 3/8" feed to the pump, a 1/4" return from the pump back to the tank and a 5/16'' vent line that runs to the charcoal canister under the hood in the front left corner.

There is a sheetmetal plate that is bolted above the rear axle on the right side. Under that protective cover is the fuel line rubber hoses. You will need to remove that cover to access and disconnect the rubber hoses from the tank's fuel pickup. Should be three rubber hoses under that cover. Then you have a three line pickup.

The reason to replace the pickup?
Bob

Fuel gauge not working, sitting on full, if I disconnect and ground the wire at the tank it goes to empty so the gauge is working, the wire is good, that leaves the sending unit, Correct?

Should be two wires from the tank's sending unit. One is the BLACK with a WHITE stripe, this is the ground. it is grounded to the frame near the tank filler neck. T he other is a PINK, this has a plug, this PINK runs to the fuel gauge. Unplug the PINK wire at the plug and using a VOM measure the resistance between the PINK from the tank and the BLACK/WHITE ground. At a fill tank of fuel should have 90 ohms. Empty a reading of near zero ohms should be had. A 1/2 tank would be in the area of 45 ohms. If you have the meter connected and shake the car side to side at the back to slosh the gas you shock see a up and down change of the meter reading. Not a lot but some varying of the meter.

Generally most times the tank sender isn't the problem. The BLACK/WHITE ground wire at the frame back at the filler neck is often the problem. Clean that connection and install little dielectric grease on the connection.
The connection of the cluster's 13 wire plug at the bottom right corner of the cluster can also be an issue. Lightly pressing in that lower right bottom cluster corner may show a connection problem. Be aware all the plastic dash parts are fragile.
My fuel gauge erratic behavior was caused by the connection of the fuel gauge to the cluster printed circuit and the metal clips that make that connection to the plastic printed circuit were loose. That was like 15 years ago. I cleaned the sender ground, replaced the sender and still that same problem, erratic gauge measurements. Bought a new gauge thinking it was the problem and when I removed the cluster found the loose connection on the printed circuit. Fix that and never had a problem since. Original gauge went back in at that time.

One other problem common to the gauges of the 80's GMs is in the gauges is a viscous fluid, maybe liquid silicone, used internally to dampen the movement of the needle. It can leak out over time and needles will get jumpy. Can be noticeable when turn signal is blinking causing a voltage to rise and drop in the cluster printed circuit. Gauges with leaked dampen fluid will have needles that jump to the tune of the turn signal blinking. Years ago had all 6 gauges in the stock cluster re calibrated and refaced, 180 speedo, 80 psi oil and 8k tach and found two gauges were in tune with the blinking turn signal. Had to replace both of those gauges and a dissection of the jump gauges showed the fluid leak problem. Just some FYI.

I later did a complete 1/2" fuel system upgrade to an FI tank and also an aftermarket 1/2" tank pickup and have the second OEM tank unit sitting in the shop, still nice condition it you think you need to drop the tank because of a faulty pickup. Most people today will use the Spectra Premium FG08A. 3 tube, as a replacement. It WAS made in Canada, but who knows now. GM #25001613 was the original tank pickup number, paid 77 bucks for one in 1998.

Borrow a VOM and check the sender resistance numbers before you drop the tank.
If you ground that PINK wire to the chassis that would show zero resistance to the gauge and it should read empty. If you were to install a 90 ohm resistor would show full, or one 50 the gauge should show 3/4 tank. So a 20 ohm resistor would show give or take a 1/4 tank.

Dropping the tank is not a big deal, just much easier if it doesn't have much gas in it. After 30+ years of road use there will be a lot of dirt on the top side of the tan, be aware.
Bob

Bob,
Finally got time to check the ground today, the connection looked pretty nasty. I disconnected it and used a wire wheel on the frame, the same on the bolt till it looked new. I just went ahead and cut off the ring terminal on the wire and replaced it with a new one. Hooked it all back up and rats! same problem so will be dropping the tank to replace the sending unit. I would have cleaned up that connection anyway for the new sending unit so no labor lost there, thanks for the tip, it had me hopeful but no dice.
I do have a cycle jack so should make dropping the tank less of a hassle since it has more than twice the support area of a floor jack, sold the Harley a few years but hung on to the jack. Was very handy when I replaced the in-tank fuel pump on my F-150.
I will probably try the resistor test before I actually drop the tank just to be sure. My back doesn't like doing work that my brain can do with no lifting involved.

Carl