Late Model TBI Tank/Sender swap questions

[goathearder]

Hey Guys,
I am about 70% done with the TBI swap on my 73 and have a few questions regarding the tank and sender. I bought a brand new tank and sender with in-tank pump for a 90 Blazer and they fit like a glove but this is whats stumping me:

1) Wiring - On the 73 I have a wire for fuel level sender and ground. On the new sender there are 3 wires, Black - Ground, Tan - Assuming this is the Fuel Pump + and Purple - Assuming this is the fuel level sender wire

Can anyone verify my wiring assumptions? I am pretty sure its right but wanted to triple check.

2) My old fuel tank has this isolation material on it where the straps go and also at the top. I know you can get this stuff from LMC but I don't want to wait that long, is there anything local I can get that will do the trick?


Thanks,
John

 

[dyeager535]

Roofing felt will work for the straps, I jsut happened to have some lying around. I painted the tank where the straps ride before installation as that was the only place my tank was really rusty.

I wouldn't assume anything with electrical, but I believe you are correct on wiring. You can check resistance on the wires to ensure that the one you assume is the fuel gauge is indeed. Or, jumper that wire with the known gauge wire, and see which one reads correctly. Make sure your ground is good first.

 

[goathearder]

Roofing felt huh? Can you get that at like Home Depot or Lowes? I've never heard of it before.

If I check resistance, what should I expect for the sender wire with an empty tank?

 

[dyeager535]

I can never remember on the resistance values. I know the gauge reads 0-90 ohms, so empty is either 0 or 90 or higher If the tank is out you can simply flip it over if you don't want to pull the sender again...the resistance should go the opposite direction.

I'm not sure if buying roofing felt is cost effective, but if you are in a hurry...

Here are some other options: http://coloradok5.com/forums/showthread.php?t=113283&highlight=roofing A mountain bike tube may be wide enough if split in half. Not sure how badly the roofing stuff retains moisture, but I would think it would eventually dry out, where rubber against metal would probably retain water indefinitely, IF it got between the two.

 

[goathearder]

Ok, this is perfect. Home depot should definitely have something.

Great idea on just flipping it, that will narrow it down for sure!

 

[K85 Octane]

if the color wiring is still up in the air when I get home, I'll check, but flipping the tank will at least show which one is for the sender

get it done J
this weekend I'm back at the blazer, gotta finish!

 

[goathearder]

I'm almost there. Hopefully tonight it'll be running under its own fuel injected power.

I'm gonna make myself hold off on the 700R4 and NP205 swap for a month so I can enjoy the truck for a while, hahahaha.

 

[goathearder]

Just to finish this up for future searches my assumptions above were correct. After measuring the resistance I confirmed:

Purple wire = Sender wire
Tan wire = Fuel Pump positive

 

[goathearder]

One more update to this thread for future reference. The filler neck on the 73 is 1.5 inches but on the 91 tank its 1.75 inches. Just a heads up for anyone doing the swap. I was able to get some 1.75 inch hose at a marine supply place, then got a piece of 1.75 inch OD exhaust tubing and a silicon 1.5 to 1.75 inch reducer to fit the new tank to the original filler.

 

[4X4HIGH]

One more update to this thread for future reference. The filler neck on the 73 is 1.5 inches but on the 91 tank its 1.75 inches. Just a heads up for anyone doing the swap. I was able to get some 1.75 inch hose at a marine supply place, then got a piece of 1.75 inch OD exhaust tubing and a silicon 1.5 to 1.75 inch reducer to fit the new tank to the original filler.

Fuel filler hose is special so I hope you bought the correct hose otherwise you're in for fun.

 

[goathearder]

Yea, i bought marine fuel filler hose so it should do the trick.