85 K 10 Fuel Gauge issue

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Cutman

Junior Member
Joined
Jan 5, 2023
Posts
1
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Location
Texas
First Name
Vince
Truck Year
1985
Truck Model
K10
Engine Size
350
Hello. My first post although have been an avid reader of the forum and it has been very useful, thanks to all of you!
I have an 1985 K10 born a 6.2 diesel, dual tanks. When I purchased it, someone had swapped a 92 TBI motor in. (Have a 6.0 & 4L80 just not ready to devote the time for the swap yet)
I am running off the LH tank and it was plumbed to run off of LH tank prior to me. I put a fuel pump and sending unit for an 87 Blazer in LH tank. The truck runs fine on the fuel pump.
I can't get the gauge to come off 3 o'clock. Grounding gauge (Pink wire) does send it to empty. The resistor on the back of the gauge reads 90 ohms. I have checked and all grounds are good, no breaks in wire from sending unit to gauge. I pulled the cluster out and had to replace the plug in connector and verified pins are all in the right place. Connection at fuse block is good.
The Pink wire from sending unit goes to the fuse block, then up to cluster. The wiring for the dual tanks, cab switch and the solenoid switch are still on the truck. I've connect the Pink/white wire to Pink, Pink/black wire to Pink, tan wire to Pink (Individually, not all at once) still reads at 3 o'clock.

Let me know if anyone knows what I am missing from above.

Last question. I can't find how many Ohms the 87 Blazer sending rheostat unit is putting out per factory spec. Could this be the issue not being 90 like the resister on the back of the gauge.
please help, it's driving me nuts and taking way to long to figure out.
 

75gmck25

Full Access Member
Joined
Oct 13, 2016
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Location
Northern Virginia
First Name
Bruce
Truck Year
1975
Truck Model
K25 Camper Special TH350 NP203
Engine Size
5.7
Not sure about an ‘87, but in past years the wire for the fuel gauge was always tan for the main tank and tan/white stripe for the other side. Pink is probably related to the switching solenoid to switch between tanks.
 

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